Tweet WHY ARE TESTS SO IMPORTANT? Modern growing practices include scientific evaluations of soil, water, fertilizers, diseases, etc. While some tests are best performed by a laboratory, others can be easily conducted on location, saving time and money. Three tests in particular, EC, pH, and ALKALINITY, […]
WHY ARE TESTS SO IMPORTANT?
Modern growing practices include scientific evaluations of soil, water, fertilizers, diseases, etc. While some tests are best performed by a laboratory, others can be easily conducted on location, saving time and money. Three tests in particular, EC, pH, and ALKALINITY, can reveal valuable information about water quality, soil salinity, and fertilizer concentration. Our portable AGRI-METERS™ provide you with a simple, fast, and accurate means of testing these parameters.
WHAT IS ELECTRICAL CONDUCTIVITY (EC)?
EC is the measurement of a solution’s ability to conduct an electrical current. For horticultural applications, the unit of measure is often expressed as millimhos. Absolutely pure water is actually a poor electrical conductor. It is the substances (or electrolytes) dissolved in the water which determine how conductive the solution will be.
Therefore, EC can be an excellent indicator of:
1. Water quality
2. Soil salinity
3. Fertilizer concentration
EC AND WATER QUALITY
The quality of irrigation water is one of the most critical factors influencing your growing operation. It is important to have a complete water analysis performed on a regular basis. Environmental conditions such as drought, changing seasons, heavy rainfall, etc., can cause the concentrations of dissolved salts in your water to vary significantly. These dissolved salts (i.e. calcium, sodium, etc.) can directly affect your plants’ health and, over time, render even the best soil useless.
You can monitor your overall water quality by testing its electrical conductivity with an AGRI-METER™. The higher the EC, the more salts are dissolved in your water. By comparing your EC with previous readings, you can tell if any dramatic changes have occurred. Nutrient deficiencies are possible when water is too pure (low EC) or if the relative concentrations of some nutrients are unbalanced (i.e. calcium/magnesium). On the other hand, nutrient toxicities or osmotic interferences can also be traced to water quality. Water EC of even one millimho or below can cause problems. High EC readings of more than two millimhos can suggest serious problems, and special cultural procedures may be required.
EC AND SOIL SALINITY
“Water, water, everywhere, but not a drop to drink” is an old saying that applies to your plants when the soil salinity becomes too high. Salts from irrigation water and fertilizers tend to accumulate in your soil or growing media. High soil salinity disrupts the normal osmotic balance in plant roots. In severe cases a plant will become dehydrated even when the soil is wet. Symptoms of high soil salinity include: leaf chlorosis and necrosis, leaf drop, root death, nutrient deficiency symptoms, and wilting. All too often these symptoms are not recognized as being caused by soluble salts in the growing media. Sampling your soil and testing the EC of an extract can reveal important information about a soil’s suitability and your crop’s health.
Samples should be representative of different depths and locations. An easy-to-perform extract method is available with a Soil Test Kit. A 2:1 or 5:1 water-to-soil ratio is made using the small vials provided. Soil test labs often use a method that calls for testing the EC of an extract from a thicker slurry. Therefore, you may see higher soil EC readings from a lab. It is important to standardize your sampling, extract, and testing methods. This will keep the difference between lab and field testing to a predictable factor.
EC AND FERTILIZER CONCENTRATION
You know how important fertilizer is to your plants, but do you know how accurate your fertilizer dosage is? Relying on traditional proportional methods is risky to plants and can waste expensive fertilizer. Improperly mixed fertilizer or a malfunctioning injector can lead to less than optimal results or even a disastrous loss of crops. Many fertilizer companies now recommend using a simple EC test to verify correct fertilizer concentrations. Many growers check their fertilizer injectors on a weekly basis, or they use a continuous EC monitor.
Fertilizer companies and suppliers often can provide a chart relating EC to parts per million concentrations of their various fertilizers. If one is not available for the fertilizer you use, carefully make some stock solutions at commonly used strengths and test their EC. This will give you a data base for future reference.
To test the EC of fertilizer solutions:
- Test and record the EC of the water to be mixed with the fertilizer.
- Test the conductivity of the fertilizer and water mixture.
- Subtract the water conductivity determined in #1 above.
- The resulting figure is an accurate indication of how much fertilizer is present (a higher conductivity means more fertilizer).
Important note: Interpretation of results differs from formula to formula and even among manufacturers of the same formula. Obtain the proper EC charts from the fertilizer company.
Myron L Meters sells both portable and inline instrumentation to make your fertilizer monitoring easy. Myron L AGRI-METERS™, AG-5 and AG6/PH, TH1, waterproof TECHPRO II™ models TP1, TPH1 and TH1, and waterproof ULTRAMETER II™ models 4P and 6PFCEare handheld instruments which make fertilizer testing as simple as filling a cup and pushing a button.
The Myron L 750 Series II™ EC Monitor/controllers can be used to continuously monitor your fertilizer concentration. Their “alarm” relay circuit acts as a safeguard in a fertilizer injection system or even as the main controller for your injector. A 0-10 VDC output for chart recorders or PLC (SCADA) input is standard on all monitor/controller models.
IMPORTANCE OF pH
pH, the measure of acidity or basicity, should be included in any soil or water test. It is well documented that growing media pH is critical to successful plant growth. This is especially true for new soilless mixes and hydroponics. pH affects the roots’ ability to absorb many plant nutrients. Examples include iron and manganese, which are insoluble at high pHs and toxic at low pHs. pH also directly affects the health of necessary micro-organisms in soil.
The effectiveness of pesticides and growth regulators can be severely limited by spray water pH that is either too low or too high.
It is important to note that testing the pH of irrigation water reveals only part of the story. Testing water alkalinity (bicarbonates and carbonates) is much more important than generally recognized. Alkalinity dictates how much influence the water’s pH will have on your soil and nutrient availability. In addition, alkalinity has a very great effect on the ease or difficulty of reducing the pH of water.
TweetWhen disaster strikes, people are scared and disorganized. They need resources — safe water and proper sanitation — that aren’t easy to come by in the aftermath. Without the help of humanitarian organizations to provide assistance, large populations of survivors are subject to epidemics of cholera, diarrhea, meningitis, and other diseases as they struggle to […]
When disaster strikes, people are scared and disorganized. They need resources — safe water and proper sanitation — that aren’t easy to come by in the aftermath. Without the help of humanitarian organizations to provide assistance, large populations of survivors are subject to epidemics of cholera, diarrhea, meningitis, and other diseases as they struggle to meet these basic needs.
Dr. Roddy Tempest, a leading designer and manufacturer of water purification systems has headed the efforts of public and private aid organizations, such as the United Nations and AmeriCares, in responding to people in crisis all over the world for over 15 years.
Dr. Tempest contributed his expertise and experience in such situ- ations as the aftermath of Hurricane Andrew in 1992, the Kosovar refugee crisis in the Balkans, the devastating earthquakes in Tur- key and the flood and mudslides that ravaged the coastal states of Venezuela in 1999. He has assisted in disaster relief efforts in Japan, Africa, Central America, and Taiwan, as well.
So when AmeriCares launched its water purification program for the inhabitants of Sri Lanka following the devastation of the tsunami on December 26, 2004, it turned to Dr. Tempest.
For this heroic effort, Dr. Tempest used two Ultrameter II 6P portable, handheld water testing instruments. Dr Tempest said the instruments gave him “a good, quick first-brush assessment of the possible water sources.”
The Ultrameter II reported and recorded instant precise measurements of Conductivity, Resistivity, TDS, ORP (REDOX), pH, and Temperature. But creating a livable situation for hundreds of thousands of displaced survivors wasn’t as easy as testing the water.
Water Doctor to the Rescue
From his offices in the United States, Dr. Tempest responded to the call for help by first reviewing satellite maps that showed the location of potential water sources in relation to groups of survivors, or Internally Displaced Persons (IDPs). He assessed the total situation of the potential water sources, trying at a glance to deter- mine possible contamination by flooding or infiltration of seawater. Upon his arrival in Sri Lanka, Dr. Tempest worked 24 hours a day to determine a suitable survival supply of water for the IDPs. As indicated in the World Health Organization’s Environmental Health in Emergencies and Disasters, the required water per person per day is 15 liters / 3.963 gallons.
Faced with this daunting task, Dr. Tempest surveyed the land via helicopter and fixed wing aircraft to record the extent of the damage, the location of IDPs, and the viability of potential water sources. Some of the photographs reveal the mammoth challenge he had ahead of him. Debris lay everywhere, indicating the likelihood of surface water and well contamination. Filtration was a must.
Dr. Tempest then combined satellite imagery, the photographs and sketches of water sources from his survey and a list of supplies to determine which water sources would be targeted for testing.
Following World Health Organization guidelines, Dr. Tempest considered as many potential water sources as possible, not just the most obvious ones. These included surface and groundwater near the groups of IDPs and tankered or bottled water brought in from a distance – though this would not be suitable for the long- term supply. The preferred source would have been groundwater, especially for the long-term.
Ultrameter II in Action
Dr. Tempest used the Ultrameter II 6P to screen these sources for their potential disinfection and filtering.
First, Dr. Tempest considered whether or not potential water sources could be protected from pollution and secured. Any potential source water had to be filterable and sanitizable. If the water was brackish, it would require a certain treatment method. If it was high in turbidity, then it would require another. If the pH needed adjusting, then yet another. If the source water was not easily treatable, then the source had to be discarded as an option and a better alternative found.
The Ultrameter II provided Dr. Tempest with fast, reliable, accurate initial information on whether or not to pursue further testing and treatment of a potential source. Dr. Tempest used a multiparameter approach and tested for Total Dissolved Solids (TDS), pH, ORP (REDOX), and temperature (recorded with every reading taken.) He also tested for turbidity and bacteria using other instrumentation.
Initially, Dr. Tempest used a measurement of the mineral salt concentration using TDS calibrated to a sodium chloride solution and TDS calibrated to a natural water standard.
Right away Dr. Tempest knew whether or not the water was too saline or saturated to be filtered economically. If the TDS is too high, filtration systems that work by reverse osmosis can be overwhelmingly expensive to operate in a disaster area, especially considering electrical costs alone. At the very least, the systems become less efficient as the TDS increases and a burden in operation and maintenance costs. This is critical for the short-term disaster response, where Dr. Tempest has to get as much safe water to IDPs in as short amount of time as possible.
High TDS can also indicate an unacceptable level of specifically known inorganic contaminants caused by industrial pollution.
And though it is not a health consideration, high TDS water often has an unpleasant taste that deters people from using it. People may try to return to old wells or other sources of previously safe drinking water that have been contaminated in the disaster. The old source may be more trusted than one that tastes “polluted.” So even though TDS is a secondary water quality standard, it can profoundly impact whether or not the new source is acceptable.
Dr. Tempest also took instant electronic pH readings using the Ultrameter II. The pH directly affects the potential to disinfect the water. pH levels beyond 8 will require substantial increases in the amount of disinfectant required or the length of time the water must be disinfected before safe consumption. And at a pH beyond 9, a residual disinfectant is extremely difficult to maintain.
pH is also critical in the long-term disaster recovery planning. pH that is too low or too high affects water balance, as well, and can contribute to either corrosion or scaling of filtration and disinfection system components and plumbing. An electronic meter is the best choice in this application as compared to colored strips or solutions or other colorimetric methods that do not produce the accuracy required to consistently and correctly balance water and maintain proper disinfection levels. The more precisely the pH is maintained, the less costly safe water production is.
Dr. Tempest also took quick ORP (REDOX) measurements using the Ultrameter II. ORP (REDOX) is the oxidation reduction potential of the water and indicates the state of the water for gaining or losing electrons. Unlike pH, which measures the water’s ability to donate or receive hydrogen ions, ORP (REDOX) values reflect the presence of all oxidizing and reducing agents — not just acids and bases. Initially, the ORP (REDOX) value gave Dr. Tempest a rough idea of the organic load in the water. A reading of 650 mV or greater indicated good water quality that could effectively be sanitized by a minimal amount of free chlorine. A value like 250 mV indicated that the organic contaminants would significantly increase chlorine demand and thereby significantly increase operation and management costs.
ORP (REDOX) is not only a good first indicator about the viability of a water source, but it also is the best way of measuring the disinfectant present in the water after treatment has begun.
Putting It All Together
Using all of the results from these parameters and based on his knowledge of the location of IDPs in relation to potential water sources, Dr. Tempest decided which source would satisfy the needs of each specific location of groups of IDPs. Where possible, water treatment technology would be designed around the quality of the source waters tested where IDPs had gathered, since it was not practical to re-locate large groups of people to distant water sources. Unfortunately, in the case of the Tsunami in Sri Lanka, oftentimes the water closest to IDPs could not be filtered and relocation was necessary.
Dr. Tempest found after his first quick assessment of potential water sources that it was not practical to supply the IDPs in parts of the Batticoloa and Ampara Districts along the eastern coast, because the source water was too saline from seawater intrusion. With limited electricity, this
made the use of reverse osmosis or desalination equipment impractical.
He ended up settling on sites that were more inland, using source waters from man-made reservoirs. IDPs were then settled inland near the cleaner water source.
However, the water in the man-made reservoirs was heavily contaminated with toxic blue-green algae.
Dr. Tempest chose microfiltration and ultrafiltration water treatment systems in the eastern district locations, taking algae-infested water over the salt-saturated, so that treatment and operation costs would be significantly less. Dr. Tempest designed, built and commissioned 4 large transportable water treatment systems, each capable of producing over 500,000 liters/day.
Plans then continued to follow through with long-term water treatment using the Tempest Environmental Systems equipment for the Sri Lankan Ministry of Urban Development and Water Supply and their National Water Supply & Drain- age Board (NWSDB). The NWSDB has 14 Ultrameter II 6Ps in current use in Sri Lanka, which are providing continuing confidence checks to ensure system equipment remains up and running properly.
The Ultrameter II 6P is an excellent multiparameter water quality meter used by thousands of water treatment professionals. The instrument can test for pH, total dissolved solids, conductivity, resistivity, oxidation reduction potential, temperature, and has the capability of testing for free chlorine. This meter handles the job of SIX single parameter testers using one single water sample. Save 10% on the Ultrameter II 6P at MyronLMeters.com.
Tweet1. Introduction The economic development of any region, state or country, depends not only on its natural resources and productive activities, but also on the infrastructure that account for the exploitation, processing and marketing of goods. Irrigation systems, roads, bridges, airports, maritime, land and air transport, school buildings, offices and housing, industrial installations are affected […]
The economic development of any region, state or country, depends not only on its natural resources and productive activities, but also on the infrastructure that account for the exploitation, processing and marketing of goods. Irrigation systems, roads, bridges, airports, maritime, land and air transport, school buildings, offices and housing, industrial installations are affected by corrosion and therefore susceptible to deterioration and degradation processes.
Corrosion is a worldwide crucial problem that strongly affects natural and industrial environments. Today, it is generally accepted that corrosion and pollution are interrelated harmful processes since many pollutants accelerate corrosion and corrosion products such as rust, also pollute water bodies. Both are pernicious processes that impair the quality of the environment, the efficiency of the industry and the durability of the infrastructure assets. Therefore, it is essential to develop and apply corrosion engineering control methods and techniques.
Other critical problems, that impact on infrastructure and industry are climate change, global warming and greenhouse emissions, all interrelated phenomena.
This post presents important aspects of corrosion in industrial infrastructure, its causes, impacts, control, protection and prevention methods.
1. Materials in industry
Metallic materials play a key role in the development of a country and its sustained growth in the context of the global economy. Table 1 shows a classification and the properties of different types of materials used in the industry. During the course of the metal production it undergoes various types of processes: mining of minerals, manufacturing and application and generation of gases, liquids or solids that are released into the environment. In the industrial development, production and use of materials in general, economic cycles are due to take effect that influence the environment (Raichev et al., 2010). The selection of a predominant group of materials depends on the particular industries; they determine to a greater or lesser extent the pattern of consumption of a given product, inducing the market to adapt itself to this new reality. The materials industry follows two general strategies: re‐ search the materials and the available technology recommended for their. Recycled materi‐ als typically require less capital and energy consumption, but need more manpower, for primary processing. Also, the costs of pollution control are lower than those required for primary processing of minerals. Recycling becomes more intense, as economies tend to be more sophisticated, since viable quantities of recycled material must be available for reuse (Garcia, R., et al, 2012, Lopez, G. 2011, Schorr, M., 2010).
In the production of a material waste is generated: for example, parts of material that was left aside, through the production steps. There are called effluent, which consist of waste that comes from the processes linked to the technology involved in each step of production, although not necessarily with the main material. Industrial processes for the recovery of ore from the mine to produce a metal, are related to technological development and therefore varies from one country to another, including regulatory laws, financial aspects etc.. Therefore, the environmental impacts vary widely. A low grade or poor quality of the ore, with low metal content, increase the cost of recovery, requiring large amounts of mineral raw material and en‐ ergy invested for the recovery of small amounts of metal. Also important is the feasibility of the mineral that can be worked out e.g., the cost of physical removal of rock, accessibility to the mines, thickness and regularity of the ore zone, and its hardness. Figure 1, shows the material cycle, which involves processes from raw material, extraction from natural sources, processing and conversion into industrial materials, their processing and application, the deterioration rate effects, its mechanical properties, environmental behavior, corrosion, disposal and possible recovery of some of these through the use of recycling methods.
There are many examples of recovery of metals, which could help to describe step by step the various interactions with the environment itself. A mineral submitted to a production process will impact the environment, during four steps: extraction, processing, fabrication and manufacturing, of goods as seen in the cycle of materials. (Figure 1)
In the mineral extraction step, the effluents of N, C, S, NOx, SOx and COx, from machinery and equipment, operation process water, particulate matter and ground movement in landfills.
The processing stage, chemical operations or extractive metallurgy for converting the concentrate into metal apply selected technologies. The effluents are gases such as SO2, NO2 and CO2, water contaminated with heavy metals, and hazard sediments.
In the manufacturing step the material undergoes operations that transform it into rods, bars, sheets; losses are scrap metal, such as cuts, burrs, mill scale, which recycled with no net loss of metal. In the manufacturing stage the metal is formed by stamping, machining and forging.
Focus on good operations management involves control of air emissions, water management and treatment, solid waste disposal and good land use, will greatly help to maintain a good balance with the environment. It is also necessary to analyze the production area to identify what improvements or measures should be implemented. The role of hydrometallurgist is particularly important and so he is responsible for the design of environmentally friendly processes in each of his steps, to promote sustainable production.
2.1 Processes of materials biodeterioration in industrial systems
In addition to the common processes of deterioration of materials by chemical reactions and mechanical fracture, there are others who are concerned with the participation of various types of microorganisms that adhere in colonies or develop on their surfaces.
Biocorrosion and biodeterioration of metallic materials and nonmetallic materials are two important processes that cause serious problems to the infrastructure of various industrial systems. Generally, microorganisms do not deteriorate or corrode metals directly, but modify the conditions of interface material / environment and surroundings, favoring the degradation of these materials in such a way that induce or influence the development process.
Biofouling is a common term that indicates the presence of microbiological growth on the surfaces of structures built of different materials favoring the formation of biofilms with the colonies of various types of microorganisms.
In the case of metal, biocorrosion occurs due to corrosion electrochemical processes and bio‐ logical agents due to the action of microorganisms and / or bacteria present in the system. The knowledge of these biological processes and their effects is necessary in order to establish preventive measures and control measures in industrial systems.
An industrial plant containing several biocorrosion environments is a potential risk:
In a heat exchangers system, usually dust accumulates biological waste; biocorrosion could occur, leading to corrosion film formation on walls surface. Therefore, it will be energy loss by increasing the resistance to fluid flow and heat transfer. Loss by evaporation of water favors the increase of the concentration of nutrients, the residence time, the water temperature and the surface / volume ratio, which leads to higher rate of microbial growth (Stoytcheva et al., 2010, Carrillo M. et al., 2010).
Until the early 80′s of the twentieth century, we used mixtures of anodic and cathodic inhibitors, such as chromium, zinc and phosphates, to lessen the effects of corrosion in water systems. In some cases we added a polymer, as is still done to date, to avoid or eliminate the problems of fouling on the metal walls. On the other hand, to prevent microbiological growth, we added biocides such as chlorine and quaternary ammonium compounds under acidic conditions.
In the early 90′s, the strategies for industrial water treatment changed because of pressure from laws for the preservation of the environment. Chromates and acid pH values are replaced by the use of organic phosphonates as corrosion inhibitors, while for the control of fouling polycarboxylate type polymers are used. However, this change brought about an increase in the amount of suspended solids, a greater number and variety of microorganisms and therefore a greater amount of inorganic deposits on the heat exchangers walls.
2.2. Biodeterioration of metallic and nonmetallic materials
The metal nature has an effect on the distribution and development of microbial films on its surface. These films influence on the wear and corrosion of the metal substrate. The lack of homogeneity in the biofilm is a precursor of differential aeration processes with formation of differential cell concentration, for example, stainless steels (SS) and nickel-copper (Ni-Cu) alloys in seawater. The oxides passive films or hydrated hydroxides (corrosion products) are a good place for the establishment and growth of bacteria, especially when these products are at a physiological pH values (pH ≈ 7.4)
- Carbon Steel (CS)
CS are very active metals in aggressive media, such as seawater. In this case, the action of microorganisms involves the dissolution of films of corrosion products, by processes of oxidation and reduction. This creates new metal active areas, exposed to the aggressive medium and suffers corrosion processes. In the case of sulfate-reducing bacteria (SRB), the species generated by their metabolism (sulfides) are corrosive to the metal. Figure 2 shows the final state pitting outside a CS pipe, which was affected by microbial growth inside, prompting a process of microbial corrosion with not uniform localized attack.
- Stainless steel
The presence of chromium and molybdenum as alloying elements, enable passive behavior of stainless steels in different environments. However, the passive surface of these SS provides an ideal location for microbial adhesion and therefore are susceptible to corrosion pit‐ ting, crevice corrosion under stress or in solutions containing chlorides, as sea water.
In marine environments, the generation of peroxides during bacterial metabolism causes an ennoblement of the pitting potential of SS, thus promoting corrosion. Obviously, not all SS have the same behavior, but in general they tend to deteriorated in the presence of colonies of microorganisms.
- Copper and nickel alloys
Alloys of Cu with Zn, Sn and Al, brasses, bronzes, aluminum bronzes; also the nickel alloys: Monel, Hastelloy, nickel superalloys: Ni-Mo, Ni-Cr-Mo, Ni-Cr-Fe- Mo; the traditional nickel alloys: Ni-Cr-Fe, Ni-Fe-Cr, Fe-Ni-Cr-Mo), and the Cu-ni alloys CuNi\70/30, CuNi\90/10, have shown great corrosion resistance in different environments, so they have found a wide use in different industries and environments. However, despite these skills, there are reports that these alloys are colonized by bacteria after several months of exposure in seawater (Acuña, N. et al., 2004).
- Aluminum and its alloys
Al is an active metal which is passivated rapidly in some neutral and acid media, thus offer‐ ing a good resistance to corrosion. Al alloys with copper, magnesium and zinc, are widely used in the aviation industry. However, there have been cases of biocorrosion on fuel tanks of jet aircraft made of Al alloys by microbial contaminants in turbo combustibles. The presence of water (moisture), even in minimal amounts, allows growth of microorganisms (typically fungi), when these are able to utilize hydrocarbons as a carbon source.
Ti is considered as the most resistant metal to biocorrosion, according to the results of tests carried in different conditions, due to its passive behavior that is reinforced in the presence of oxidizing agents. This is the reason why Ti is the material of choice, for example, for the manufacture of tubes in cooling systems that use seawater.
- Nonmetallic materials
Non-metallic materials such as fiberglass reinforced polyester (FGRP), concrete and wood, are also affected by biodeterioration processes in the presence of microorganisms
In the case of FGRP, bacteria and algae are able to use the polyester matrix as a carbon source, consuming and considerably reducing the mechanical strength of composite material, ultimately causing its failure. This is easily observable in screens of this material in cool‐ ing towers or tanks containing fresh water or salt water. Wood suffers biodeterioration by the presence of fungi in moist environments that promote the delignification of this material (Valdez B., et al., 1996, 1999, 2008).
2.2. Facing the problems of biodeteriorationThe inevitable presence of microorganisms in the feed water causes a sequence of biofouling, biocorrosion and biodeterioration of the materials component of the structures. This sequence depends on the degree of microbial contamination and the system operating characteristics.
The most common methods of controlling these problems involve the application of continuous or metered biocides such as chlorine. Currently, we use substances more compatible with the environment, since the use of chlorine is limited to certain concentrations. Such is the case of ozone, which is also ascribed with passivating effects on certain metals and alloys commonly applied in industry, and also in antifouling action.
In order to tackle a biodeterioration problem it is required a prior analysis of the problem, to know when conditions are suitable for the development of this process. In industrial systems we need to know some parameters: temperature, pH, nutrients; carbon, phosphorus, nitrogen, sulfate ion levels and flow rates. The places where we find biodeterioration are: biofouling deposits, under any deposit, zones of localized metal corrosion. to check their presence it is necessary to utilize sampling techniques, isolation and identification of micro‐ organisms. It is interesting to note that there are commercial devices for in situ measurements that are practical and useful for the plant engineer.
1. Corrosion in the electronics industry
Corrosion of device components, manufactured by the electronics industry, is a problem that has occurred during a long time. Often, especially corrosion of one or more of the metallic ele‐ ments of an electronic component is the primary cause of failure in various electronic equip‐ ments. The high density of components required to reduce the size of electronic equipment, also for a better signal processing, leads to the generation of enclosed corrosion between thin metal sections. Furthermore, when electronic devices are in more severe environments such as tropical, subtropical, contaminated deserts, etc., they have high failure rates. Problems, due to the aggressiveness of the medium in electronic equipment for military use, have also occurred in aircraft and submarine guidance systems. Another common problem is corrosion damage suffered by components music players, when exposed to humid environments contaminated with chlorides, for example, during transport by ship, from the manufacture location to the consumer place. Thin layers of corrosion products on the surface of the metal component change their electrical characteristics: resistance, capacity and lead to partial or total failure of the electronic system. There are reported cases where small amounts of moisture have caused corrosion in tablets with printed circuits, nichrome resistors, fittings, electrical connectors and a wide range of components, and micro-electronic components, which have been coated with metallic films (Valdez B. et al., 2006, G. Lopez et. al., 2007)
Corrosion of metal components in the electronics industry may occur at different stages: during manufacture, storage, shipping and service. The main factors in the onset of corrosion and subsequent development are moisture and corrosive pollutants, such as chlorides, fluorides, sulfides and nitrogen compounds, organic solvent vapors, emanating from the resins used as label, or coatings formed during the curing process and packaging of microcircuits.
The sources providing aggressive pollutants are diverse, from flux residues used for welding processes, waste and vapors from electrolytic baths, arising volatile organic adhesives, plastics and acidification of their environment. Assays in artificial atmosphere, which simulates an in‐ door environment of an electronic plant have shown that the surface of the silver undergoes browning or tarnishing and the formation of dendrite whiskers due to corrosion (Figure 3).
The elemental chemical analysis of the surface (EDX – Scattered Electron Spectroscopy and XRD – X-rays) shows that the corrosion product formed on the silver surface is silver sulfide (Ag2S), due to the action of pollutant gases such as SO2 and H2S present in a humid environment (Figure 4). Moreover, the micrograph of the silver surface (SEM) shows a dendritic growth of corrosion products, characteristic for silver components.
The design of electronics equipment requires a great variety of different metals, due to their different physical and electrical features. Metals and alloys used in the electronics industry are:
- Gold (Au) coating and / or foil in electrical connectors, printed circuits, hybrid and miniature circuits.;
- Silver (Ag) for protective coating in contact relays, cables, EMI gaskets, etc..;
- Magnesium (Mg) alloys for radar antenna dishes and light structures, chassis brackets, etc..;
- Iron (Fe), steel and ferroalloys for guide components, magnetic shielding, magnetic coatings memory disks, processors, certain structures, etc..;
- Aluminum (Al) alloys for armor equipment, chassis, mounting frames, brackets, trusses, etc..;
- Copper and its alloys for cables, tablets printed circuit terminals, nuts and bolts, RF pack‐ aging, etc..;
- Cadmium (Cd) for sacrificial protective coating on iron and safe electrical connectors;
- Nickel (Ni) coating for layers such as barrier between copper and gold electrical contacts, corrosion protection, electromagnetic interference applications and compatibility of dis‐ similar material joints;
- Tin (Sn) coating for corrosion protection of welding; for compatibility between dissimilar metals, electrical connectors, RF shielding, filters, automatic switching mechanisms;
- Welding and weld coatings for binding, weldability, and corrosion protection.
Many of these metals are in contact with each other, so that in the presence of moisture, galvanic corrosion / bimetallic corrosion occurs. When using similar metals, due to design the following requirements must be taken into account.
- Designing the contact of different metals such that the area of the more noble cathodic metal should be appreciably smaller than the area of the more active anodic metal. The area of the cathode can be decreased by applying paint or coating.
- Coating the contact area of a metal with a compatible metal.
- Interpose between dissimilar metals in a metal compatible packaging.
- Sealing interfaces to prevent ingress of moisture.
- Set the electronic device in a hermetically sealed arrangement.
Other corrosion problems can occur due to the characteristics of electronic components such as electromagnetic interference, electromagnetic pulse, flux residues, finishes and materials component tips, organic products that are used for various purposes and emitting gases during curing, whiskers, embrittlement inter-metallic electrical contacts.
Metal components may corrode during manufacture and storage prior to assembly, needing protection against corrosion. In plants and warehouses, air conditioning systems must operate efficiently, removing moisture and suspended particulate matter. Filters and traps should be cleaned and replaced regularly. For closed containers, we recommend the installation of dryers with visual indicators, and the use of volatile vapor phase corrosion inhibitors. In the case of sealed black boxes, the temperature inside these drops should never be below the dew point (Veleva L. et al., 2008, Vargas L. et al., 2009, Lopez G. et al., 2010).
1. Corrosion in water
Abundant water sources are essential to a country’s industrial development. Large quantities of this precious liquid are required for cooling products, machinery and equipment, to feed boilers, meet health needs and provide drinking water to humans. Estimates of water consumption for each country are different and depend on the degree of industrial development thereof. In first world countries like the United States, these intakes are as high as several hundred billion liters per day. These countries have implemented water reuse systems with certain efficiency due to the application of appropriate treatment for purification. Water, a natural electrolyte is an aggressive environment for many metals / alloys, so that they may suffer from corrosion, whose nature is electrochemical.
As raw water or fresh water we mean natural water from direct sources such as rivers, lakes, wells or springs. Water has several unique properties and one of these is its ability to dis‐ solve to some degree the substances found in the earth’s crust and atmosphere allowing the water to contain a certain amount of impurities, which causes problems of scale deposition on the metal surface, e.g. in pipelines, boiler tubes and all kinds of surfaces that are in con‐ tact with water (Valdez, B. et al., 1999, 2010).
Oxygen is the main gas dissolved in water, it is also responsible for the costly replacement of piping and equipment due to its corrosive attack on metals in contact with dissolved oxygen (DO). The origin of all sources of water is the moisture that has evaporated from the land masses and oceans, then precipitated from the atmosphere. Depending on weather conditions, water may fall as rain, snow, dew, or hail. Falling water comes into contact with gas‐ es and particulate matter in the form of dust, smoke and industrial fumes and volcanic emissions present in the atmosphere.
The concentrations of several substances in water in dissolved, colloidal or suspended form are low but vary considerably. A water hardness value greater than 400 parts per million (ppm) of calcium carbonate, for example, is sometimes tolerated in the public supply, but 1 ppm of dissolved iron should be unacceptable. In treated water for high pressure boiler or where radiation effects are important, as in nuclear reactors, impurities are measured in very small amounts such as parts per billion (ppb).
In the case of drinking water the main concern are detailed physicochemical analysis, to find contamination, and biological assays to detect bacterial load. For industrial water supplies it is of interest the analysis of minerals in particular salts. The main constituents of water are classified as follows:
- Dissolved gases: oxygen, nitrogen, carbon dioxide, ammonia and sulfide gases;
- Minerals: calcium, sodium (chloride, sulfate, nitrate, bicarbonate, etc.), Salts of heavy metals and silica;
- Organic matter: plant and animal matter, oil, agricultural waste, household and synthetic detergents;
- Microbiological organisms: include various types of algae, slime forming bacteria and fungi.
The pH of natural waters typically lies within the range of 4.5 to 8.5; at higher pH values, there is the possibility that the corrosion of steel can be suppressed by the metal passivation. For example, Cu is greatly affected by the pH value in acidic water and undergoes a slight corrosion in water releasing small amounts of Cu in the form of ions, so that it’s corroded surface because green stained clothing and sanitary ware. Moreover, deposition of the Cu ions on surfaces of aluminum or galvanized zinc corrosion cells leads to new bimetallic con‐ tact, which cause severe corrosion in metals.
The mineral water saturation produces a greater possibility of fouling on the metal walls, due to the ease with which the insoluble salts (carbonates) can be precipitated. To control this effect it is necessary to know and use the Saturation Indices. Water saturation refers to the solubility product of a compound and is defined as the ratio of the ion activity and the solubility product. For example, water is saturated with calcium carbonate when it is no more possible to dissolve the salt in water and then it begins to precipitate as scale. In fact, it is called supersaturated when carbonate precipitation occurs on standing the solution. The most common parameters that must be known to characterize the water corrosivity, be it raw or treated, for operation in an industrial facility are shown in Table 2.
There six formulas to calculate Saturation Indices and embedding: Langelier index (LSI), Ryznar stability index, Puckorious index of scaling, Larson-Shold index, index of Stiff- Davis and Oddo-Tomson index. There is some controversy and concern for the correlation of these indices with the corrosivity of the waters, particularly regarding the Langelier (LSI).
A LSI saturation index with value “0″ indicates that the water is balanced and will not be fouling, while the positive value indicates that the water may be fouling (Table 3). The negative value of the LSI suggests that water is corrosive and can damage the metal installation, increasing the content of metallic ions in water. While some sectors of the water management industry uses the values of the indices as a measure of the corrosivity of the water. Corrosion specialists are alerted and are very wary of issuing an opinion, or extrapolate the use of indices to measure the corrosivity of the environment.
Sometimes the raw water is contaminated with chemicals such as fertilizers and other chemicals coming from agricultural areas (Figure 5).
In these cases, ionic agents such as nitrites, nitrates, etc., in water causes an accelerated process of localized corrosion to many metals and the consequent failure of equipment.
Raw water contaminants can be quite varied, including both heavy metals and organic chemicals, referred to as toxic pollutants. Among the heavy metals may be mentioned arsenic (As), mercury (Hg), cadmium (Cd), lead (Pb), zinc (Zn) and cadmium (Cd), which are sometimes at trace levels, but they tend to accumulate over time, so that priority pollutants are to be treated.
Pesticides, insecticides and plaguicides comprise a long list of compounds, for which we should be concerned: DDT (insecticide), aldrin (an insecticide), chlordane (pesticide), endo‐ sulfan (insecticide), diazinon (insecticide), among others.
Contaminants, such as polycyclic aromatic organic compounds, include what is known as volatile organic compounds such as naphthalene, anthracene and benzopyrene. There are two main sources of these pollutants: petroleum and combustion products found in munici‐ pal effluents. On the other hand, there are polychlorinated biphenyls or PCBs, which are mainly used in transformers for the electrical industry, heavy machinery and hydraulic equipment. This class of chemicals is extremely persistent in the environment and affects human health.
From the viewpoint of corrosion, these contaminants which are present even at low concentrations or trace in the raw water, favor the corrosivity the metals which are in contact with. The combination of the corrosive effects of these contaminants together with the oxidation by oxygen, minerals and other impurities, leads to consider raw water as a natural means capable of generating corrosion of metals. It is recommended at least, to carry out a process of treating raw water, to reduce significantly the hardness and remove suspended solids, which will help greatly in preventing subsequent problems of corrosion and fouling on metal surfaces, curbing economic losses and maintaining the industrial process in good operating condition.
4.1. Corrosion in potable water systems
Corrosion is a complex phenomenon that arises as a result of the interaction between water and the surface of metallic pipes or the equipment of storage and handling. The process is invariably a combination of oxidation and reduction, as already described in previous chapters. In drinking water, it should be noted that the corrosion products which are partially soluble in water in ionic form are toxic at certain concentrations, e.g. copper and lead. The existence of high concentrations of lead in water carried by copper tubing, indicate that the source of lead may be tin-lead solder at the junctions of the copper pipes. The consumption of domestic water contaminated with toxic metal ions (Pb+2, Cu+2, Zn+2, Cr+3), gives rise to acute chronic health problems. The regulations have set the following limits allowable concentration in drinking water: Cr (0.05 ppm), Cu (0.01 ppm), Pb (0.05 ppm) and Zn (5 ppm). These regulations are made in order to protect the public user and consumer of drinking water and are continuously striving for a reduction in the maximum allowable limits. Some concentrations reach zero as is the case of Pb in the United States due to the concerns Pb about poisoning of children. Still, many sources such as wells and springs are outside the control of law and toxic substances, bacteria and pathogens. Damage caused by corrosion of household plumbing may be accompanied by unpleasant aesthetic problems such as soiled clothing, unpleasant taste, stains and deposits in the toilets, floors of bathrooms, tubs and showers. To prevent corrosion of pipes, we recommend the use of PVC pipes for drinking water, replacing the metal, as a preventive measure.
Corrosion can occur anywhere on the pipes that carry drinking water, mainly at sites of con‐ tact between two dissimilar metals, thus forming a corrosion cell. In general, the metals will corrode to a greater or lesser degree in water, depending on the nature of the metal, on the ionic composition of water and its pH. Waters high in dissolved salts (water hardness), favor the formation of scale, more or less adherent, in different parts of the equipment (Figure 6). These deposits may be hard or brittle, sometimes acting as cement, creating a physical barrier between the metal and water, thereby inhibiting corrosion. Calcium carbonate (Ca‐ CO3) is the most common scale; its origin is associated with the presence of carbon dioxide gas (CO2) in water. Sometimes these deposits are filled with pasty or gelatinous hydrated iron oxides or colonies of bacteria (Valdez, B. et al., 1999, 2010).
Usually, groundwater CaCO3 saturated (calcareous soils), due to the presence of dissolved CO2, whose content depends on its content in the air in contact with the water and on temperature. These waters are often much higher in CO2 content, so they may dissolve substantial amounts of calcium carbonate. These waters are at pressures lower than they had in the ground, so CO2 gas lost with consequent supersaturation of carbonates. If conditions are appropriate, the excess of CaCO3 can precipitate as small agglomerates deposited in muddy or hard layers on solid surfaces, forming deposits. An increase in temperature is an important factor and also leads to supersaturation of carbonates, with the consequent possibility of fouling. To a lesser extent fouling can precipitate more soluble Mg carbonates (MgCO3) and Mn (MnCO3), and also oxides / hydroxides, dark colored and gelatinous. Except in very exceptional cases in sulfated water, it is normal to find deposits of gypsum (CaSO4•½ H2O) because their solubility is high, but decreases with increasing temperature. Hard silica scale (SiO2) may appear with oversaturated waters or appear as different silicates (SiO44-) trapped in the carbonate deposits. Generally, the silica appears trapped in other types of scale and it is not chemical precipitation.
Waters often carry considerable amounts of iron (ferrous ion, Fe+2), which may be often precipitated by oxidation upon contact with air as hydrated iron oxide (ferric, Fe+3) but sometimes can be Fe+2 form black sludge, more or less pasty or gelatinous and sometimes very large. The voluminous precipitate occupies the pores, significantly reducing the permeability of the fouling. Sometimes the Fe ions can come from corrosion of the pipe giving rise to simultaneous corrosion and scaling (Figure 6). Common bacteria of the genera Gallionella, Leptothrix Cremothrix are known as Fe bacteria, can give reddish-yellow voluminous precipitate and sticky ferric compounds from ferrous ion, which drastically reduce the permeability of the deposit, in addition to trap other insoluble particles.
The cost for impairment of domestic water systems and the impact on health, involves several consequences: premature corrosion and failure of the pipes and fittings that carry water in a house or building, a low thermal efficiency (up to 70%) of water heaters (boilers), which can cause their premature failure. High levels of metals or oxides, which usually are not properly, treated in drinking water cause red or blue-green deposits and stains in the toilets sinks. In addition to concerns about the aesthetic appearance, a corrosion process can result in the presence of toxic metals in our drinking water. For evaluating water quality and their tendency corrosive and / or fouling, LSI can be used. This analysis must be accompanied by measurements of water pH and conductivity, and corrosion tests applying international standards.
4.1. Anticorrosive treatment of water Corrosion control is complex and requires a basic knowledge of corrosion of the system and water chemistry. Systems can be installed for water pretreatment, using non-conductive connections, reducing the temperature of hot Cu water pipes employed and copper installing PVC or other plastic materials. It is important to note that the corrosiveness of water can be increased by the use of water softeners, aeration mechanisms, increasing the temperature of hot water, water chlorination, and attachment of various metals in the water conduction system. A proper balance between the treatment systems and water quality, can be obtained with acceptable levels of corrosivity. Thus, the lifetime of the materials that make the water system in buildings, public networks, homes and other systems will be longer.
1. Soil corrosion
A large part of steel structures: aqueducts, pipelines, oil pipelines, communications wire ropes, fuel storage tanks, water pipes, containers of toxic waste, are buried, in aggressive soils. Large amounts of steel reinforced concrete structures are also buried in various soil types. In the presence of soil moisture it is possible to have humid layer on the metal sur‐ face, whose aggressiveness depends on soil type and degree of pollution (decaying organic matter, bacterial flora, etc.). Thus, the soil can form on the metal surface an electrolyte complex with varying degrees of aggressiveness, a necessary element for the development of an underground electrochemical corrosion. The corrosion process of buried structures is extremely variable and can occur in a very fast, but insignificant rate, so that pipes in the soil can have perforations, presenting localized corrosion attack or uniform.
Metal structures are buried depending on their functionality and security. Most often they traverse large tracts of land, being exposed to soils with different degrees of aggressiveness exposed to air under atmospheric conditions (Figure 7).
When pipes or tanks are damaged by corrosion, the formation of macro-and micro-cracks can lead to leaks of contained products or fluids transported, causing problems of environmental pollution, accidents and explosions, which can end in loss of life and property (Guadalajara, Jalisco, Mexico, 1992). In the case of pipes used to carry and distribute water, a leak may cause loss of this vital liquid, so necessary for the development of society in general and especially important in regions where water is scarce, so the leakage through aqueducts pipes should be avoided. An important tool needed to prevent the most serious events, is the knowledge of the specific soil and its influence on the corrosion of metal structures.
5.1. Types of soils and their mineralogy
A natural soil contains various components, such as sand, clay, silt, peat and also organic matter and organisms, gas, mineral particles and moisture. The soils are usually named and classified according to the predominant size range of individual inorganic constituent particles. For example, sandy soil particles (0.02 – 2 mm) are classified as fine sand (0.02 – 0.2 mm) or thick (0.20 -2.00 mm). Silt particles (0.002 to 0.02 mm) and clay, which have an average diameter 0.002 mm, are classified as colloidal matter. A comparison of the sizes of these typical soils is done in Figure 8.
Currently exists in the U.S. and in over 50 countries worldwide, a detailed classification for soils, which includes nine classes with 47 subgroups.
The variation in the proportion of the groups of soil with different sizes, determines many of its properties. Fine-textured soils due to high clay content, have amassed particles, so they have less ability to store and transport gases such as oxygen, that any ground-open e.g. sandy soil. The mineralogy of both clay types and their properties, are closely related to the corrosivity of the soil. Silica (SiO2) is the main chemical constituent of soils type clay, loam and silt, also in the presence of Al2O3. Common species in moist soil are dissolved ions H+, Cl-, 2- -SO4 , HCO3 . The chemical composition and mineralogy of the soil determine its corrosive aggressiveness; poorly drained soils (clay, silt and loam) are the most corrosive, while soils with good drainage (gravel and sand type) are less aggressive to metals. Vertically homogeneous soils do not exist, so it is convenient to consider the non-uniformity of ground, formed of different earth layers. To understand the corrosion behavior of a buried metal is very important to have information about the soil profile (cross section of soil layers). The physicochemical and biological nature of soil, corrosive aggressiveness and dynamic interactions with the environment, distinguishes the ground like a very complex environment and different from many others. Climate changes of solar radiation, air temperature and relative humidity, amount of rainfall and soil moisture are important factors in corrosion. Wind, mechanical action of natural forces, chemical and biological factors, human manipulation can alter soil properties, which directly affects the rate of corrosion of metals buried in the ground. Conditions may vary from atmospheric corrosion, complete immersion of the metal, depending on the degree of compactness of the soil (existence of capillaries and pores) and moisture content. Thus the variation in soil composition and structure can create different corrosion environments, resulting in different behavior of the metal and oxygen concentrations at the metal / soil interface.
Two conditions are necessary to initiate corrosion of metal in soil: water (moisture, ionic conductor) and oxygen content. After startup, a variety of variables can affect the corrosion process, mentioned above, and among them of importance are the relative acidity or alkalinity of the soil (pH), also the content and type of dissolved salts.
Mainly three types of water provide moisture to the soil: groundwater (from several meters to hundreds below the surface), gravitational (rain, snow, flood and irrigation) and capillary (detained in the pores and capillary spaces in the soil particles type clay and silt). The mois‐ ture content in soils can be determined according to the methodology of ASTM D 2216 (“Method for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass”), while its permeability and moisture retention can be measured the methods descri‐ bed in ASTM D2434 and D2980. The presence of moisture in soils with a good conductivity (presence of dissolved salts), is an indication for high ion content and possible strong corrosive attack.
The main factors that determine the corrosive aggressiveness of the soil are moisture, rela‐ tive acidity (pH), ionic composition, electrical resistance, microbiological activity.
5.1. Corrosion control of buried metals
Given the electrochemical nature of corrosion of buried metals and specific soils, this can be controlled through the application of electrochemical techniques of control, such as cathodic protection. This method has been universally adopted and is appropriate to protect buried metallic structures. For an effective system of protection and cheaper maintenance, pipelines must be pre-coated, using different types of coatings, such as coal tar, epoxies, etc. This helps reduce the area of bare metal in direct contact with the ground, lowering the demand for protection during the corrosion process. The purpose of indirect inspection is to identify the locations of faulty coatings, cathodic protection and electrical Insufficient shorts (close- interval, on/off Potential surveys, electromagnetic surveys of attenuation current, alternating current voltage gradient surveys, etc..), interference current, geological surveys, and other anomalies along the pipeline.
1. Corrosion under thermal insulation
One of the most common corrosion problems in pipes, ducts, tanks, preheaters, boilers and other metal structures, insulated heat exchange systems, is the wear and corrosion occurring on metal (steel, galvanized steel, Al, SS, etc.), below a deposit or in its immediate neighbor‐ hood. This corrosion is known as corrosion under deposit. The deposit may be formed by metal corrosion products and / or different types of coating applied for protection. For ex‐ ample, in the case of a calcareous deposit, formed in the walls of galvanized steel pipes which carry water with a high degree of hardness (dissolved salts), it might develop corro‐ sion under deposit. These shells may be porous, calcareous deposit and / or partially detach‐ ed from the metal surface, so that direct contact between metal, water and oxygen (the oxidizing agent in the corrosion process) allows the development of metal corrosion. For this reason the pipes could be damaged severely in these locations up to perforation, while in parts of the installation corrosion might occur at a much lower level.
There is a considerable amount of factors in the design, construction and maintenance, which can be controlled to avoid the effects of deterioration of metal by corrosion under de‐ posit. In general, under these conditions the metal is exposed to frequent cycles of moisture, corrosivity of the aqueous medium or failure in the protective coatings (paint, metal, ce‐ ment, fiberglass, etc.). Figure 9 shows a conductor tube steam in a geothermal power plant, where CS corrosion happened beneath the insulation.
Seven factors can be controlled on the ground, to prevent this type of corrosion: design of equipment, operating temperature, selection of the insulation, protective coatings and paints, physical barriers from the elements, climate and maintenance practices of the facility. Any change in any of these factors may provide the necessary conditions for the corrosion process to take place. The management knowledge of these factors help explain the causes of the onset conditions of corrosion under deposits, and it will guide a better inspection of existing equipment and the best design.
6.1. Equipment design
The design of pressure vessels, tanks and pipes, generally includes accessories for support, reinforcement and connection to other equipment. Details about the installation of accessories are the responsibility of the engineers or designers, using building codes to ensure reliability of both insulated and non insulated equipment. The protective barrier against the environment surrounding the metal structure in such designs often breaks donor due to an inappropriate insulation, loss of space for the specified thickness of insulation or simply by improper handling during installation of the equipment. The consequence of a rupture or insulation failure means greater flow water ingress to the space between metal and coating hot-cold cycle, generating over time a buildup of corrosive fluid, increasing the likelihood of corrosive damage. Moreover, wet insulation will be inefficient and also cause economic loss‐ es. The solution of this factor is to meet the thickness specifications and spacing, as indicated in the code or equipment-building specifications and characteristics of the coating used.
The operating temperature is important for two reasons: a high temperature favors the wa‐ ter is in contact with the metal for less time, however, also provides a more corrosive environment, causes fast failures of coatings. Usually a team operating in freezing temperatures is protected against corrosion for a considerable life time. However, some peripheral devices, which are coupled to these cold spots and operating at higher temperatures, are ex‐ posed to moist, air and steam, with cycles of condensation in localized areas, which make them more vulnerable to corrosion. For most operating equipment at freezing conditions, the corrosion occurs in areas outside and below the insulation. The temperature range where this type of corrosion occurs is 60 °C to 80 °C; however, there have been failures in zones at temperatures up to 370 °C. Also, in good water-proof insulation, corrosion is likely to occur at points where small cracks or flaws are present, so that water can reach the hot metal and evaporate quickly. On the other hand, in machines where the temperature reach‐ es extreme values, as in the case of distillation towers, it is very likely to occur severe corro‐ sion problems.
6.2. Selection of insulation
The characteristics of the insulation, which have a greater influence on the corrosion proc‐ esses deposits, are the ability to absorb water and chemical contribution to the aqueous phase. The polyurethane foam insulation is one of the most widely used; however, in cold conditions they promote corrosion due to water absorption present. The coatings of glass fi‐ ber or asbestos can be used in these conditions, always when the capacity of absorbing wa‐ ter do not becomes too high. Corrosion is possible under all these types of coating, such insulation. The selection of insulation requires considering a large group of advantages and disadvantages regarding the installation, operation, cost, and corrosion protection, which is not an easy task. The outside of the insulation is the first protective barrier against the ele‐ ments and this makes it a critical factor, plus it is the only part of the system that can be readily inspected and repaired by a relatively inexpensive process. The durability and ap‐ pearance, melting point fire protection, flame resistance and installation costs are other im‐ portant factors that must be taken into account together with the permeability of the insulation. Usually the maintenance program should include repairs to the range of 2 to 5 years. Obviously the weather is important and corrosion under thermal insulation will more easily in areas where humidity is high. Sometimes conditions of microclimate can be ach‐ ieved through the use of a good design team.
1. Corrosion in the automotive industry
One of the most important elements of our daily life, which has great impact on economic activity, is represented by automotive vehicles. These vehicles are used to transport people, animals, grains, food, machinery, medicines, supplies, materials, etc. They range from com‐ pact cars to light trucks, heavy duty, large capacity and size. All operate mostly through the operation of internal combustion engines, which exploit the heat energy generated by this process and convert it in a mechanical force and provide traction to these vehicles.
The amount and type of materials used in the construction of automotive vehicles are diverse, as the component parts. They are usually constructed of carbon steel, fiberglass, aluminum, magnesium, copper, cast iron, glass, various polymers and metal alloys. Also, for aesthetic and protection against corrosion due to environmental factors, most of the body is covered with paint systems, but different metal parts are protected with metallic or inorganic coatings.
Corrosion in a car is a phenomenon with which we are in some way familiar and is perhaps for this reason that we often take precautions to avoid this deterioration problem.
A small family car, with an average weight of 1000 kg, is constructed of about 360 kg of sheet steel, forged steel 250 kg, 140 kg cast iron mainly for the engine block (now many are made of aluminum), 15 kg of copper wires, 35 kg and of plastic 50 kg of glass that usually do not deteriorate, and 60 kg for rubber tires; which wear and tear. The remaining material is for carpets, water and oil. Obviously, that is an advanced technology in the car industry, with automobiles incorporating many non-metallic materials into their structure. However, the problem of corrosion occurs at parts where the operation of the vehicle is compromised. Corrosion happens in many parts of the car (mostly invisible) it is not only undesirable for the problems it causes, but also reduces the vehicle’s resale value and decreases the strength of the structure. To keep the car in good condition and appearance, its high price, it is neces‐ sary to pay attention to the hidden parts of the vehicle.
The main cause of corrosion of the car body is the accumulation of dust in different closed parts, which stays for a long time by absorbing moisture, so that in these areas metal corrosion proceeds, while in the clean and dry external parts it does not occur (Figure 10).
The corrosion problem that occurs in the metal car body has been a serious problem that usually arises most often in coastal environments, contaminated with chlorides and rural areas with high humidity and specific contaminants. Many countries use salt (NaCl, CaCl2 or MgCl2) to keep the roads free of ice; under these conditions these salts, in combination with the dust blown by the car, provide conditions for accelerated corrosion. Therefore, it is recommended as a preventative measure, after a visit on the coast or being on dirty roads, to wash the car with water, and also the tires and the doors, especially their lower parts. In urban environments, the corrosion problem has been reduced due to the new design and application of protective coatings, introduced by major manufacturers in the early nineties of the twentieth century. The areas most affected are fenders, metal and chrome bumpers views which are used in some luxury vehicles as well as areas where water and mud are easily accumulated e.g. auctions of funds windshield and doors (Figure 11).
In regions with high incidence of solar radiation and the presence of abrasive dust, paint vehicles deteriorate rapidly. The hot, humid weather, combined with high levels of SO2 and NOx emissions that come from burning oil, chlorides salt. In the Gulf of Arabia, the blowing sand from the nearby desert, creates a very aggressive environment; statistics reveals that one in seven cars is damaged and due to corrosion the car life is estimated to an average of 8 months, also the car corrosion resistance decreases in the following order: manufactured in Europe, USA and Japan. White paints generally have shown a significantly better corrosion protection than other colors. Initially, corrosion defects appear as a kind of dots and spots of corrosion products formed under the paint and subsequently emerge from the steel sheet, leaving a free entry for moisture and air (oxygen), accelerating the corrosion process; in these cases reddish metal corrosion products.
7.1. Corrosion in the cooling systemThe cooling system of a car combustion engine consists of several components, constructed of a variety of metals: radiators are made of copper or aluminum, bronze and solder couplings with tin water pumps; motors are made of steel, cast iron or aluminum. Most modern automobiles, with iron block engine and aluminum cylinder head, require inhibitor introduced into the cooling water to prevent corrosion in the cooling system. The inhibitor is not antifreeze, although there are in the market solutions which have the combination of inhibitor-antifreeze. The important thing is to use only the inhibitor recommended in the automobile manual and not a mixture of inhibitors, since these may act in different ways and mechanisms. The circulating water flow should work fine without loss outside the system. If the system is dirty, the water should be drain and filling the system with a cleaning solution. It is not recommended to fill the system with hard water, but with soft water, introducing again the inhibitor in the correct concentration. If there exhaust at the water cooling system, every time water is added the inhibitor concentration should be maintained to prevent.
In small cars, it is common for water pumps; constructed mainly of aluminum, to fail due to corrosion, cavitation, erosion and corrosion, making it necessary to replace the pump (Val‐ dez, B. et al., 1995). Accelerated corrosion in these cases is often due to the use of a strong alkaline solution of antifreeze. On the other hand, in heavy duty diesel trucks, the cooling system is filled with tap water or use filters with rich conditioner chromates that can cause the pistons jackets to suffer localized corrosion. After 12 or 15 months, the steel jackets are perforated and the water passes into the cavity through which the piston runs, forcing tocarry out repair operations (Figure 12).
Corrosion causes great economic losses to the transport industry, since it must stop to repair the truck and abandon to provide the service with all the consequences that this entails. Fur‐ thermore, the use of chemical conditioning is now controlled by environmental regulations, so chromates and phosphates are restricted and novel mixtures of corrosion inhibitors have been produced to control the problem of corrosion in automobile cooling systems.
7.1. Corrosion in exhaust pipes and batteries
Exhaust pipes made of SS (0.6 – 0.8 mm thick) have a better resistance to chemical corrosion at high temperatures, which is why we are now using SS in many popular models. This SS resists corrosion much more than conventional CS and thus their long life covers the higher price. An‐ other alternative is to use conventional CS tube, zinc coated or aluminum (Figure 13). These ex‐ haust pipes are less expensive than stainless steel, but less resistant to corrosion.
The acidic environment which is generated on the surface of accumulators supplying the energy necessary for starting the engine, favors conducting corrosion processes in the lead terminals, where the cables are connected by bronze or steel clamps. Thus, this environment and these contact zones predispose cells to a process galvanic corrosion, which gradually deteriorates the contact wires, generating bulky corrosion products. This phenomenon is called sulfation of the contacts due to the sulfuric acid containing the battery, thus forming white sulfates on the corroded metal surface. These products introduce high resistance to current flow and cause failure to the engine ignition system, and impede the battery charge process. This problem has been eliminated in batteries that have airtight seals, or are manufactured with new technologies as well as bases covered with organic coatings that prevent corrosion.
Some years ago it was common for starters to fail, because the moisture or water penetrated into the gear area preventing it sliding motion and causing burning of the electric motor. Currently, new designs avoid contact with moisture and other foreign agents, preventing the occurrence of corrosion problems in these devices. As a preventive measure is recommended to prevent spillage of battery acid, to periodically clean the battery terminals (with a brush of wire or a special instrument), also coat them with petroleum jelly to prevent corrosion in these contact areas. A fat based composition which contains several components: alkaline salts and oxides of lithium, sodium bicarbonate and magnesium oxide are applied to the terminals and the connector. In general, in wet weather, the contacts of the accumulators have a tendency to more accelerated corrosion, thus requiring greater care to disconnect the terminals when not being used.
7.1. Corrosion prevention
To keep the vehicle for a longer time without the appearance of corrosion, it always requires washing with running water and, the use of very soft brush or cloth-like material, with a special detergent (not household detergents, which are very corrosive) and finally wash the vehicle with plenty of water. The floor carpet should be maintained clean and dry. A car should not be left wet in a hot garage, since under these conditions accelerated corrosion takes place since the water does not dry and can condense on the cold parts of the vehicle. In these cases, it is best not to close the garage door or use a roof space, to protect it from rain, and not allow moisture condensation. However, if the vehicle is left unused for a long time in a closed garage, it should be protected from dust, moisture and contaminants.
1. Corrosion control in thermoelectric plantsElectricity is a key element in ensuring economic growth and social development of a country. Many conventional power plants in recent years are being installed in combined cycle power plants, also called cogeneration. The latter, simultaneously generate electricity and / or mechanical power and useful heat, sometimes using thermal energy sources that are lost in conventional plants.
A power station is a thermoelectric energy conversion system, starting with the chemical energy of fuel that during combustion is converted into heat energy accumulated in the steam. This thermal energy generates mechanical energy from the hot steam, which expands in a turbine, turning on electricity in the generator. In this process of low energy thermal efficiency is lost in the hot gases that escape through the chimney and the cooling steam in the condenser.
Electricity generating plants burn fossil fuels such as coal, fuel oil and natural gas. These fuels containing as minor components sulfur compounds (S), nitrogen (N), vanadium (V) and chloride (Cl-). These are corrosive chemicals attacking the metal infrastructure; and polluting the environment by becoming acid gas emissions, also affecting the health of the population.
The three central equipment of a thermoelectric plant are the boiler, which converts the wa‐ ter into steam, the steam turbine to whom the pressure imparts a rotary motion and the con‐ denser that condenses the vapor released by the turbine and the condensed water is returned to the boiler as feed water. The turbine itself transmits rotary motion to the genera‐ tor of electricity, which will be distributed to industrial, commercial and homes in cities.
Corrosion in steam plant equipment occurs in two parts of the boiler: on the water side and the steam side, with the fire temperature up to 700 ° C, depending on the type, size and ca‐ pacity of the boiler. The boiler feedwater must be treated to eliminate the corrosive components: salts such as chlorides and sulfates dissolved oxygen (DO); silicates and carbonates, producing calcareous scale on the boiler walls, regarded as precursors for the formation of corrosion under deposits. The water is softened by eliminating salts and treated to remove oxygen; the pH is controlled by addition of alkaline phosphate to reach a pH range of 10 to 11, and inhibitors are added to the feedwater to prevent corrosion.
The flue gases and ash solid particles reach temperatures up to 1000 to 1200 °C, impinging on the outer surface of the boiler water tubes and preheater, creating an atmosphere for aggressive chemical corrosion. The damaged tubes lose its thickness generating metal corrosion products; they often are fractured, suffering a stress corrosion due to the combined effects of mechanical stress and corrosion (Figure 14). Since the tubes lose steam and pres‐ sure, the operation of the plant is interrupted and the tubes or its sections should be changed incurring severe economic losses. For example, in the United States has been concluded that the costs of electricity are more affected by corrosion than any other factor, contributing 10% of the cost of energy produced.
A study reveals that in 1991 there were more than 1250 days lost in nuclear plants operating in the United States, due to failure by corrosion, which represented an economic loss of $250.000 per day. Such statistics indicate that the power generation industry needs to obtain a balance between cost and methods for controlling effectively corrosion in their plants. It is sometimes advisable to add additives to the fuel, for example, magnesium oxide which prevent the deposition of the molten salts on the boiler tubes. Corrosion occurs also in the combustion air preheater, by sulphurous gases which react with condense and form sulfuric acid. Metal components of the turbine rotor: disks and blades suffer from corrosion by salts, alkali and solid particles contained in the vapor. In these cases, it is common to observe the phenomena of erosion-corrosion, pitting and stress corrosion fracture; their damage can be ameliorated through a strict quality control of boiler water and steam.
Efficient maintenance and corrosion control in a power plant is based on the following:
- Operation according to mechanical and thermal regime, indicated by the designer and builder of the plant;
- Correct treatment of fuel, water and steam;
- Chemical cleaning of the surfaces in contact with water and steam, using acidic solutions containing corrosion inhibitors, passivating ammoniacal solutions and solutions;
- Mechanical cleaning of surfaces covered with deposits (deposits), using alkaline solutions and water under pressure;
- Perform an optimum selection of the materials of construction for the components of the plant, including those suitable as protective coatings.
- The installation of online monitoring of corrosion in critical plant areas will be one of the most effective actions to control corrosion. In addition, it is recommended same use and document to use corrosion expert system software and materials databases for the analy‐ sis of the materials corrosion behavior.
Corrosion in power plants can be controlled by applying the knowledge, methods, stand‐ ards and materials, based on corrosion engineering and technology.
1. Corrosion in geothermal environments
The development of alternative energy sources represents one of the most attractive challenges for engineering. There are several types of renewable energies already in operation, such as wind, solar and geothermal. Geothermal environments can lead to aggressive environments, e.g. the geothermal field of “Cerro Prieto”, located in Baja California, Mexico.
The physical and chemical properties of the vapor at “Cerro Prieto” make it an aggressive environment for almost any type of material: metal, plastic, wood, fiberglass or concrete. The typical chemical composition of a geothermal brine, is shown in Table 4. Many engineering materials are present as components of the infrastructure and field equipment, required for the steam separation, purification and posterior operations for the generation of electricity. This entire infrastructure is a costly investment and therefore, failure or stoppage of one of them, means economic losses, regardless of how vital it is to maintain constant production of much-needed electricity.
In the process of the geothermal fluid exploitation, corrosion of metal structures occurs from the wells drilling operation, where the drilling mud used, causes corrosion of pumping and piping equipment. Subsequently, when the wells pipes are in contact with the steam, they can also suffer from corrosion-erosion problems, where the corrosive agent is hydrogen sulfide. Steam separators and the pipes are exposed to problems of fouling and localized corrosion due to the presence of aggressive components such as H2S and chloride ions (Cl-), present in the wells fluid. These agents lead to the deterioration of reinforced concrete foundations supporting steel pipes, or other concrete structures used to separate steam from water and to operate steam silencers. The reinforced concrete deterioration due to steel corrosion in this aggressive environment, and the steam pressure mechanical forces lead to concrete damage with formation of cracks and fractures.
In the power plants, the observed corrosion affects components of the steam turbines, condensers and pipelines, and also the cooling towers and concrete structures inside and outside the building that houses the plant. In these cases, the effects of corrosive attack appears in the form of localized corrosion in metal walls and gas piping) or as corrosion fatigue or stress corrosion, caused by cyclic mechanical forces or residual stresses, in turbines and other metal equipment. Table 5 shows a list of equipment and materials used for construction,which are part of the infrastructure of a geothermal power (Valdez, B. et al., 1999, 2008)
The combination of an aerated moist environment with the presence of hydrogen sulfide gas (H2S) dissolved in water provides a very aggressive medium (Figure 16), which promotes the corrosion of metals and alloys, such as CS and SS. The presence of dust, from the geothermal field and condensation cycles favor the failure of protective coatings applied to steel, so that developed corrosion leads to constant repairs and maintenance of metal installations: pipes, machinery, cooling towers, vehicles, tools, fences, warehouses, etc.
Cooling towers constructed of wood, steel and fiberglass in the presence of flowing and stagnant water and air currents (induced to complete cooling fans), suffer a serious deterioration of the steel by corrosion and biodeterioration, involving a variety of microorganisms. The timber is subjected to oxygen delignification under the effect of colonies of fungi and algae, as well as fiberglass reinforced polyester screens, which deteriorate due to colonies of aerobic and anaerobic bacteria e.g. sulfate reducers.
Furthermore, carbon steels corrode in the form of delamination due to sulfate reduction processes which induce the oxidation of iron, while the SS nails and screws undergoes localized corrosion, forming pits (Figure 17)
The deterioration by microorganisms capable of living in these conditions is one of the processes that have provided more information to the study of corrosion induced by microorganisms. In “Cerro Prieto”, for example, have been isolated and studied various bacteria capable of growing even at temperatures of 70 ° C under conditions of low nutrient concen‐ trations, while in the geothermal field of “Azufres” bacteria have been isolated to survive at temperatures of 105 °C and pressures of downhole (Figure 18).
1. Corrosion in the paper industry
Corrosion of the infrastructure used in the pulping and paper industry, is another serious problem for corrosion specialists. The wide experience, gathered from cases of corrosion in the various infrastructure components of the paper industry, has provided an extensive literature on mechanisms, types and control of corrosion in this environment.
In the early 60′s of last century, when the continuous digester process was adopted, the paper industry had limited knowledge about caustic embrittlement. Currently, it is known that the digesters are subjected to caustic levels and temperatures too close to the fracture caustic range where the total relieves of stresses in the material are essential. To elucidate the mechanism of this phenomenon, it was necessary to conduct serious investigations, which subsequently provide solutions to the problem of corrosion and caustic embrittlement. Technology in the paper industry has evolved over the last forty years and in parallel we can talk about the solution of corrosion problems in different parts of its infrastructure. Components with high failure rate due to corrosion are those built of bronze, SS, cast iron. Corrosion occurs in the papermaking machinery, where the white water equipment is subjected to an aggressive environment. The metal surfaces are exposed to immersion in this water; to steam that promotes the formation of cracks, which favor the deposit of pulp and other compounds. CS undergoes rapid uniform corrosion, while the copper alloys and SS (austenitic UNS S30400 L: 18% Cr8% Ni, UNS S31600 L: 16% Cr10% Ni 2% Mo) develop localized pitting corrosion. In the mill bleach plants the pulp equipment has traditionally been made of SS which has good general corrosion resistance and weldability. The use of chlorine gas (Cl2) and oxygen in the bleach plant and pulp bleaching, favors a very aggressive oxidant and SS, as type 317 L (18% Cr14% Ni3.5% Mo). However, in the last 25 years the environment in these plants has become much more corrosive due to the wash systems employed for the paper pulp, which increased the emission of oxidizing and corrosive gas‐ es; so type “317 L” SS is not resistant and has a shorter service life. Many mills in the paper industry have opted for the use of high-alloy SS, nickel (Ni) and titanium (Ti), for better corrosion resistance in these particular environments. In general, SS exposed to corrosive environment of bleach plants are benefited by the share of chromium, nickel and molybdenum as alloying elements, which increase their resistance to the initiation of pitting and crevice corrosion. The addition of nitrogen (N) increases its resistance to pitting corrosion, particularly when it contains molybdenum (Mo). Furthermore, to avoid waste of elements such as carbon (C), where a concentration greater than 0.03%, can cause sensitization at affected by heat areas in the solder, causing the SS to be less resistant to corrosion. Other waste elements, such as phosphorus (P) and sulfur (S) can cause fractures in the hot steel, formed in the metal welding area. The corrosive environment of bleach plants contain residual oxidants such as chlorine (Cl2) and chlorine dioxide (ClO2), these are added to resists the effects of temperature and acidity, maintaining a very aggressive environment.
Corrosion also occurs in the pulping liquor facilities by sulfites, chemical recovery boilers, suction rolls and Kraft pulping liquors. The Kraft process is the method of producing pulp or cellulose paste, to extract the wood fibers, necessary for the manufacture of paper.
The process involves the use of sodium hydroxide (NaOH) and sodium sulfite (Na2SO3) to extract the lignin from wood fibers, using large high pressure digesters. High strength is obtained in the fiber and methods for recovery of chemicals explain the popularity of the Kraft process. The black liquor separated, is concentrated by evaporation and burned in a recovery boiler to generate high pressure steam, which can be used for the plant steam requirements for the production of electricity. The inorganic portion of the liquor is used to regenerate sodium hydroxide and sodium sulfite, necessary for pulping. Corrosion of metals in the facilities used in this process may occur during the acid pickling operation for the removal of carbonate incrustations on the walls and black liquor pipe heaters. It has been found that SS 304 L presents fracture failure and stress corrosion. In the recovery processes of chemical reagents, known as stage re alkalinization, metals can fail due to caustic embrittlement or corrosion-erosion under conditions of turbulent flow. Corrosion also occurs in the equipment used for mechanical pulping, such as stress corrosion cracking, crevice corrosion, cavitation and corrosion-friction.
B. Valdez1, M. Schorr1, R. Zlatev1, M. Carrillo1, M. Stoytcheva1, L. Alvarez1, A. Eliezer2 and N. Rosas3
1 Instituto de Ingeniería, Departamento de Materiales, Minerales y Corrosión, Universidad Autónoma de Baja California, Mexicali, Baja California, México
2 Sami Shamoon College of Engineering Corrosion Research Center, Ber Sheva, Israel 3 Unversidad Politécnica de Baja California, Mexicali, Baja California, México
 Acuña, N., Valdez, B., Schorr, M., Hernández-Duque, G., Effect, of., Marine, Biofilm., on, Fatigue., Resistance, of., an, Austenitic., & Stainless, Steel. Corrosion Reviews, United Kingdom (2004). , 22(2), 101-114.
 Carrillo, M., Valdez, B., Schorr, M., Vargas, L., Álvarez, L., Zlatev, R., Stoytcheva, M., In-vitro, Actinomyces., israelii’s, biofilm., development, on. I. U. D., copper, surfa‐ ces., & Contraception, Vol. (2010). (3), 261-264.
 Carrillo Irene, Valdez Benjamin, Zlatev Roumen, Stoycheva Margarita, Schorr Mi‐ chael, and Carrillo Monica, Corrosion Inhibition of the Galvanic Couple Copper-Car‐ bon Steel in Reverse Osmosis Water, Research Article, Hindawi Publishing Corporation, International Journal of Corrosion, Volume(2011). Article ID 856415
 2010, Garcia, A., Valdez, B., Schorr, M., Zlatev, R., Eliezer, A., Haddad, J., Assess‐ ment, of., marine, , fluvial, corrosion., of, steel., aluminium, Journal., of, Marine., En‐ gineering, , & Technology, Vol. (18), 3-9.
 Garcia Inzunza Ramses, Benjamin Valdez, Margarita Kharshan,Alla Furman, and Mi‐ chael Schorr, ((2012). Interesting behavior of Pachycormus discolor Leaves Ethanol Extract as a Corrosion Inhibitor of Carbon Steel in 1M HCl. A preliminary study. Re‐ search Article, Hindawi Publishing Corporation, International Journal of Corrosion, Article ID 980654, 8 , 2012, 2012.
 Lopez, B. G., Valdez, B., , S., Zlatev, R., , K., Flores, J., , P., Carrillo, M., , B., Schorr, M., & , W. Corrosion of metals at indoor conditions in the electronics manufacturing industry. Anti-Corrosion Methods and MaterialsUnited Kingdom, N0. 6, Noviembre (2007). , 54, 354 EOF-359 EOF.
 Lopez, B. G., Valdez, B., , S., Schorr, M., , W., Rosas, N., , G., Tiznado, H., , V., Soto, G., & , H. Influence of climate factors on copper corrosion in electronic equipment and devices. Anti-Corrosion Methods and MaterialsUnited Kingdom, N0. 3, (2010). , 57, 148 EOF-152 EOF.
 Lopez, Gustavo, Hugo Tiznado, Gerardo Soto Herrera, Wencel De la Cruz, Benjamin Valdez, Miguel Schorr, Zlatev Roumen,(2011). Use of AES in corrosion of copper connectors of electronic devices and equipments in arid and marine environments. Anti-Corrosion Methods and MaterialsIss: 6, , 58, 331-336.
 Lopez, Badilla Gustavo, Benjamin Valdez Salas and Michael Schorr Wiener, Analysis of Corrosion in Steel Cans in the Seafood Industry on the Gulf of California, Materi‐ als Performance, Vol.April (2012). (4), 52-57.
 Navarrete, M., Ballesteros, M., Sánchez, J., Valdez, B., Hernández, G., Biocorrosion, in. a., geothermal, power., plant, Materials., & Performance, April. (1999). USA., 38, 52-56.
 Schorr, M., Valdez, B., Zlatev, R., Stoytcheva, M., Erosion, Corrosion., in, Phosphor‐ ic., Acid, Production., Materials, Performance., & Jan, . (2010). USA, 50(1), 56-59.
 Stoytcheva, M., Valdez, B., Zlatev, R., Schorr, M., Carrillo, M., Velkova, Z., Microbial‐ ly, Induced., Corrosion, in., The, Mineral., Processing, Industry., Advanced, Materi‐ als., & Research, . (2010). Trans. Tech publications, Switzerland, 95, 73-76.
 Raicho Raichev, Lucien Veleva y Benjamín Valdez, Corrosión de metales y degrada‐ ción de materiales.Principios y prácticas de laboratorio. Editorial UABC, 978-6-07775-307-0(2009). pp
 Santillan, S. N., Valdez, S. B., Schorr, W. M., Martinez, R. A., Colton, S. J., Corrosion, of., the, heat., affected, zone., of, stainless., steel, weldments., Anti-Corrosion, Meth‐ ods., Materials, United., & Kingdom, Vol. (2010). (4), 180 EOF-184 EOF.
 Schorr, M., Valdez, B., Zlatev, R., Stoytheva, M., Santillan, N., Phosphate, Ore., Proc‐ essing, For., Phosphoric, Acid., Production, Classical., And, Novel., Technology, Min‐ eral., Processing, , Extractive, Metallurgy., & Vol, . (2010). (3), 125-129.
 Valdez, B., Guillermo Hernandez-Duque, Corrosion control in heavy-duty diesel en‐ gine cooling systems, CORROSION REVIEWS Vol.Nos. 2-4, (1995). , 245-260.
 Valdéz, Salas. B., Miguel, Beltrán., Rioseco, L., Rosas, N., Sampedro, J. A., Hernan‐ dez, G., & Quintero, M. Corrosion control in cooling towers of geothermoelectric power plants. Corrosion Reviews, (1996). England., 14, 237-252.
 Valdez, B., Rosas, N., Sampedro, J., Quintero, M., Vivero, J., Hernández, G., Corro‐ sion, of., reinforced, concrete., of, the., Rio, Colorado., Tijuana, aqueduct., Materials, Performance., & May, . (1999). USA., 38, 80-82.
 Valdez, B., Rosas, N., Sampedro, J., Quintero, M., Vivero, J., Influence, of., elemental, sulphur., on, corrosion., of, carbon., steel, in., geothermal, environments., Corrosion, Reviews., & Vol, . Nos. 3- 4, October (1999). England, 167-180.
 Valdez, S. B., Zlatev, R., , K., Schorr, M., , W., Rosas, N., , G., Ts, Dobrev. M., Monev, I., Krastev, Rapid., method, for., corrosion, protection., determination, of. V. C. I., Films-Corrosion, Anti., Methods, , Materials, United., & Kingdom, Vol. Noviembre (2006). (6), 362-366.
 Valdez, B., Carrillo, M., Zlatev, R., Stoytcheva, M., Schorr, M., Cobo, J., Perez, T., & Bastidas, J. M. Influence of Actinomyces israelii biofilm on the corrosion behaviour of copper IUD, Anti-Corrosion Methods and Materials, United Kingdom, N0. 2, 55-59, (2008). , 55
 Valdez, B., Schorr, M., Quintero, M., Carrillo, M., Zlatev, R., Stoytcheva, M., Ocampo, J., Corrosion, , scaling, at., Cerro, Prieto., Geothermal, Field., Anti-Corrosion, Meth‐ ods., Materials, United., & Kingdom, Vol. N0. 1, (2009). , 28 EOF-34 EOF.
 Valdez, B., Schorr, M., Corrosion, Control., in, The., Desalination, Industry., Ad‐ vanced, Materials., & Research, . (2010). Trans. Tech publications, Switzerland, 95, 29-32.
 Valdez, B., Schorr, M., Quintero, M., García, R., Rosas, N., The, effect., of, climate., change, on., the, durability., of, engineering., materials, in., the, hydraulic., & infra‐ structure, . An overview. Corrosion Engineering Science and Technology(2010). , 45(1), 34-41.
 Valdez, B., Schorr, M., So, A., Eliezer, A., Liquefied, Natural., Gas, Regasification., Plants, Materials., Corrosion, M. A. T. E. R. I. A. L. S. P. E. R. F. O. R. M. A. N. C. E., & Vol, . December (2011). (12), 64-68.
 Vargas, O. L., Valdez, S. B., Veleva, M. L., Zlatev, K. R., Schorr, W. M., Terrazas, G. J., Corrosion, of., silver, at., indoor, conditions., of, assembly., processes, in., the, micro‐ electronics., industry-Corrosion, Anti., Methods, , Materials, United., & Kingdom, Vol. N0. 4, (2009). , 218 EOF-225 EOF.
 Veleva, L., Valdez, B., López, G., Vargas, L., Flores, J., Atmospheric, Corrosion., of- Electronics, Electro., Metals, in., Urban-Desert, Indoor., & Environment, . Corrosion of Electro-Electronics Metals in Urban-Desert Indoor Environment. Corrosion Engineering Science and Technology(2008). , 43(2), 149-155.
This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), original found here:http://www.intechopen.com/books/environmental-and-industrial-corrosion-practical-and-theoretical-aspects/corrosion-control-in-industry
TweetFeatures • Handheld meters measure TDS and/or pH • Monitor measures TDS • All instruments are easy to operate and calibrate • High degree of accuracy • Immediate results • Kit comes with solutions required to calibrate • Temperature compensated readings TDS Monitoring The nutrient solution and its management are the foundation of a successful […]
• Handheld meters measure TDS and/or pH
• Monitor measures TDS
• All instruments are easy to operate and calibrate
• High degree of accuracy
• Immediate results
• Kit comes with solutions required to calibrate
• Temperature compensated readings
The nutrient solution and its management are the foundation of a successful hydroponics system. The function of a hydroponics nutrient solution is to supply the plant roots with water, oxygen and essential mineral elements in soluble form.
A test of the Total Dissolved Solids (TDS) using the DS Meter or pDS Meter or continuous monitoring with the HYDRO-STIK gives the grower accurate measurements of the concentration of nutrients in solution. If the concentration drops below the optimum level required to sustain and grow the plants, add more nutrient- rich solution until the desired concentration level is achieved. This prevents haphazard dosing and wasted solution, which minimizes costs to the grower.
pH of the nutrient solution is also critical to successful plant growth. All elements have a specific solubility pH range. This means that mineral elements dissolve and can become more concentrated in solution within certain pH ranges. Roots absorb only the dissolved nutrients, so this is critical to plant growth.
The TH1H and the pDS Meter quickly and easily measure pH.
Monitoring the addition of a pH balancing solution with the proper meter lets the grower precisely adjust the pH level.
Beyond affecting nutrient availability, extremely low or high pH can even damage or kill plants.
All Myron L TDS and pH meters give lab-accurate results in the field.
All Myron L meters use advanced Temperature Compensation (TC) circuitry and equations to give you the best TC correction available.
Tweet What is pH? Definition: pH is the negative logarithm of hydrogen ion activity in a solution. The Concentration ratio of hydrogen ions (H+) and hydroxyl ions (OH-) determine the pH value of a solution. Any hydrogen activity will produce a 59.16 mV/ pH unit across the glass membrane. The measurement is expressed on a […]
Definition: pH is the negative logarithm of hydrogen ion activity in a solution.
The Concentration ratio of hydrogen ions (H+) and hydroxyl ions (OH-) determine the pH value of a solution. Any hydrogen activity will produce a 59.16 mV/ pH unit across the glass membrane. The measurement is expressed on a scale of 0.0 to 14.0. Water with a pH of 7 is considered neutral (H+ ions = 10-7 and OH-
ions =10-7). A solution is considered acidic when the hydrogen ions (H+) exceed the hydroxyl ions (OH-), and a solution is considered an alkaline (base) when the hydroxyl ions (OH-) exceed Hydrogen ions (H+).
How is pH measured?
A pH instrument consists of three main components, refer to Figure 1.
1. The pH measuring cell: Hydrogen sensitive glass is blown onto the end of an inert glass stem.
A silver wire, treated with silver chloride (Ag/AgCl) is sealed inside the glass (cell) with a solution of potassium chloride saturated with Silver chloride.
The measuring solution has a neutral pH level of 7 or 0 mV. A properly hydrated glass sensor will produce a “Gel Layer” on the inside and outside of the glass membrane. The “Gel Layer” enables hydrogen ions to develop an electrical potential
across the pH glass sensor; a millivolt signal varies with hydrogen ion activity on the glass membrane while submerged in the solution being tested.
1. The Reference cell: A silver wire treated with silver chloride (Ag/AgCl) is sealed inside an inert glass housing (cell) with a solution of potassium chloride saturated with silver chloride. The inert glass prevents hydrogen ion activity from test solutions to influence the reference cells constant millivolt signal. The combination of the reference electrode silver- silver chloride wire, and the saturated potassium chloride solution develops a constant 199-millivolt reference signal. The millivolt signal produced inside the reference electrode does not vary as long as the chloride concentration remains constant. The reference voltage is used as a baseline to compare variations or changes in the solution being tested. The reference cell is in contact with the test solution through a reference junction that is commonly made of porous Teflon®*‚ ceramic, or a wick type material called a Pelon strip. This junction completes the measuring circuit of the pH sensor.
2. Display meter: When the pH sensor is placed in a solution, the pH-measuring cell develops a millivolt signal that reflects the hydrogen ion activity of the test solution. A high impedance meter accurately measures the small millivolt changes and displays the results in pH units on either an analog meter or digital display.
The pH glass membrane is sensitive to the temperatures of solutions being tested. Prolonged use and/or exposure to temperatures (above 35°C) will accelerate the aging, and increase chemical attack
to the glass membrane which will shorten the overall service life of the sensor.
ELEVATED TEMPERATURES WILL SHORTEN THE SERVICE LIFE OF A pH SENSOR.
Increase temperatures also decreases the impedance of the glass membrane. The decrease of the impedance affects the millivolt output of glass membrane.
Temperature changes close to neutral (pH 7) usually do not affect pH levels; however, when levels are
< pH 3 and > pH 11 a dramatic error may occur. This problem is resolved using a built in ATC (Automatic Temperature compensation) which uses a mathematical formula (Nernst equation) to correct pH errors due to temperature factors.
Other factors that affect the life of a sensor Because standard glass electrodes are manufactured using a silver/silver chloride electrode inserted into
a potassium chloride/silver chloride solution, the following list of solutions cause the reference solution to precipitate. If the following solutions are tested, it is recommended that the pH sensor well be thoroughly rinsed. The testing of these solutions will severely reduce the service life of the pH sensor.
1. Heavy metals – silver, iron, and lead
3. Low ion solutions – distilled water
4. High sodium concentrates
6. Fluorides (In high concentrations or prolonged use)
Note: This is not a complete list of solutions that can cause the reference solution to precipitate.
Sodium ion error
As solutions approach, and exceed the pH level of 12.0 the high concentration of sodium ions interfere with the standard glass membrane and cause pH levels to be displayed lower than actual pH levels. If solutions being tested are normally high alkaline, (>12 pH) a probe manufactured with special glass may be required. The special glass may be used throughout the pH range of 0 to 14, but due to the high resistance nature of the glass it will significantly increase the overall time to analyze a sample. Constant use in solutions with pH levels higher than 12 will reduce the life of the probe.
The break down of the pH sensor electrodes and the depletion, and/or saturation of the reference solution require your pH instrument to be re-calibrated. This should normally be performed twice a month, but depending on the actual use of the instrument it may be necessary to increase the intervals between calibrations.
Refer to your operations manual or to Myron L Meters video page for detailed instructions on your specific instrument calibration procedures. The calibration should be performed using at least two pH buffer standards. The initial calibration should use Myron L pH buffer solution 7. This will check and allow the instrument to be adjusted so its output reflects 0 millivolts, neutral, or pH 7. A second calibration using a standard solution that reflects the normal range of solutions being analyzed. If acidic solutions are normally tested, a pH buffer solution 4 should be used. If solutions to be tested are normally alkaline, a pH buffer solution 10 should be used. It is not necessary to calibrate your instrument over three standards (4, 7, and 10) unless during normal daily use of the instrument, the solutions being tested varies from low to high pH ranges. In
this case an increase of calibration intervals is also recommended.
How to maximize the life of your pH or pH/ORP sensor
Myron L uses a general-purpose glass pH sensor. This glass sensor may be used in most applications. To ensure maximum life of your Myron L pH test instruments, the following information should be considered whether you are a distributor or an end user. Most premature pH sensor failures can be prevented with a few maintenance procedures. The following procedures should be performed after using your Myron L meter, or if you plan to store your meter for an extended period of time.
1. The pH sensor well (fig 1) must be filled with
Myron L storage solution (preferred) or Myron L pH buffer 4, or tap water with table salt added and its protective cap (with foam insert) firmly installed.
Failure to do so will:
• Allow the glass membrane to dry out. A de- hydrated glass membrane will not produce the necessary “Gel layer” on the sensor surface, which is essential to allow the exchange of hydrogen ions (measure pH).
• Allow airborne contaminants to settle on the glass membrane surface. Once contaminants dry onto the surface of the glass membrane, it will inhibit the transfer of hydrogen ions. (See factory approved cleaning process below.)
• Allow the reference junction to dry out. The reference junction material is usually a wick or fiber type material that completes the electrical circuit between the reference electrode cell
and the solution being tested. Dehydration causes the reference solution to leach out of the electrode cavity, and form crystals in the junction. This is normally referred to as the “Bridging effect”.
Repeated dehydration of the pH or pH/ORP sensor will cause the instrument to have a slower response time, and be more difficult to calibrate. Dehydration will
significantly reduce the normal service life of the sensor.
2. Store spare pH or pH/ORP sensors in a refrigerator. “Do not Freeze”. Take proper precautions not to allow the temperature to fall below freezing. This
will cause the solution to expand and may damage the electrodes inside the sensor. Storage in a refrigerated environment will slow the evaporation of the storage solution, but not prevent evaporation. Always inspect and replace storage solution in spare sensor well on a regular basis.
Note: When using the Myron L storage solution, it is common for white crystal formations to form around the seal of the pH sensor well and protective cap; this is a normal occurrence as the solution evaporates. Never store the sensor in high purity water (distilled or de-ionized).
Approved factory cleaning process
Failure to do so will:
• Allow the glass membrane to dry out. A de- hydrated glass membrane will not produce the necessary “Gel layer” on the sensor surface, which is essential to allow the exchange of hydrogen ions (measure pH).
• Allow airborne contaminants to settle on the glass membrane surface. Once contaminants dry onto the surface of the glass membrane, it will inhibit the transfer of hydrogen ions. (See factory approved cleaning process below.)
• Allow the reference junction to dry out. The reference junction material is usually a wick or fiber type material that completes the electrical circuit between the reference electrode cell
and the solution being tested. Dehydration causes the reference solution to leach out of the electrode cavity, and form crystals in the junction. This is normally referred to as the “Bridging effect”.
Repeated dehydration of the pH or pH/ORP sensor will cause the instrument to have a slower response time, and be more difficult to calibrate. Dehydration will
significantly reduce the normal service life of the sensor.
2. Store spare pH or pH/ORP sensors in a refrigerator. “Do not Freeze”. Take proper precautions not to allow the temperature to fall below freezing. This
will cause the solution to expand and may damage the electrodes inside the sensor. Storage in a refrigerated environment will slow the evaporation of the storage solution, but not prevent evaporation. Always inspect and replace storage solution in spare sensor well on a regular basis.
Note: When using the Myron L storage solution, it is common for white crystal formations to form around the seal of the pH sensor well and protective cap; this is a normal occurrence as the solution evaporates. Never store the sensor in high purity water (distilled or de-ionized).
Approved factory cleaning process for the pH sensor
During normal use of your Myron L handheld pH or pH/ORP meter, you’ll have to clean your pH sensor bulb. The cleaning is necessary because of deposits left on the sensor from the test samples.
If you suspect your instrument is inaccurate, or the display value drifts, or the response is slow and sluggish, try the following.
Rinse the sensor well (three times) and fill with pH buffer 4 solution. If the pH continues to drift below the pH 4 level (i.e. 3, 2, or 1) repeat the test using pH buffer 10. If the pH level drifts beyond the pH level of 10 (i.e. 11, 12 etc.) follow the cleaning procedure outlined below.
If the pH levels of the buffer solutions 4 and 10 actually drift towards pH 7, this could mean that the pH sensor is damaged and needs to be replaced.
Caution: Wear proper eye protection and gloves during the cleaning procedure.
The following procedures may help clean and recover the pH or pH/ORP sensors.
NOTE: Not all pH or pH/ORP sensors can be recovered.
1. Fill the pH/ORP sensor well with 100% Isopropyl alcohol. If not available use additive- free rubbing alcohol (70%). This will remove any oils.
2. Allow the sensor to soak for 10 minutes.
3. Rinse with RO or DI water.
4. Rinse the sensor well (three times) and fill
with Myron L storage solution or Myron L pH buffer 4. Replace the protective cap and allow the sensor to recover overnight.
5. Re-calibrate the instrument according to the Myron L instruction manual that was provided with your instrument. If the instrument fails to calibrate properly, continue to the next step.
If the above procedure does not recover the pH sensor function, perform the following:
1. Fill the pH or pH/ORP sensor well with a hot salt solution 60°C (140°F) potassium chloride (KCI preferred) or hot tap water with table salt (NaCl). Allow the solution to cool.
2. Re-calibrate the instrument according to the Myron L instruction manual that was provided with your instrument. If the instrument fails to calibrate properly, the pH or pH/ORP sensor must be replaced.
The manufacturer warrants the pH and pH/ORP sensor assemblies against manufacturer defects. Shelf life for most pH and ORP sensors is 12 months. Failure to maintain proper hydration of the glass pH sensors or the use of the instrument in any manner not described in the operation manual supplied with the instrument may shorten the life of the sensor.
*CAUTION: If you do not use your Myron L instrument on a regular basis or if you are a stocking distributor, the storage solution in the pH or pH/ORP sensor well will evaporate over time and must be replenished. To prevent premature pH glass sensor failure, the manufacturer suggests a preventative maintenance program. Failure to do so could void the factory warranty. The use of liquids containing high levels of solvents, such as acetone, xylene, and chlorinated hydrocarbons, or other harsh chemicals in your Myron L meter is not recommended. Doing so may damage the sensor.
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TweetWastewater is treated in 3 phases: primary (solid removal), secondary (bacterial decomposition), and tertiary (extra filtration). fig. 1 Origins of Sewage Sewage is generated by residential and industrial establishments. It includes household waste liquid from toilets, baths, showers, kitchens, sinks, and so forth that is disposed of via sewers. In many areas, sewage also includes […]
Wastewater is treated in 3 phases: primary (solid removal), secondary (bacterial decomposition), and tertiary (extra filtration).
Origins of Sewage
Sewage is generated by residential and industrial establishments. It includes household waste liquid from toilets, baths, showers, kitchens, sinks, and so forth that is disposed of via sewers. In many areas, sewage also includes liquid waste from industry and commerce. The separation and draining of household waste into greywater and blackwater is becoming more common in the developed world. Greywater is water generated from domestic activities such as laundry, dishwashing, and bathing, and can be reused more readily. Blackwater comes from toilets and contains human waste.
Sewage may include stormwater runoff. Sewerage systems capable of handling storm water are known as combined sewer systems. This design was common when urban sewerage systems were first developed, in the late 19th and early 20th centuries. Combined sewers require much larger and more expensive treatment facilities than sanitary sewers. Heavy volumes of storm runoff may overwhelm the sewage treatment system, causing a spill or overflow. Sanitary sewers are typically much smaller than combined sewers, and they are not designed to transport stormwater. Backups of raw sewage can occur if excessive infiltration/inflow (dilution by stormwater and/or groundwater) is allowed into a sanitary sewer system. Communities that have urbanized in the mid-20th century or later generally have built separate systems for sewage (sanitary sewers) and stormwater, because precipitation causes widely varying flows, reducing sewage treatment plant efficiency.
As rainfall travels over roofs and the ground, it may pick up various contaminants including soil particles and other sediment, heavy metals, organic compounds, animal waste, and oil and grease. (See urban runoff.) Some jurisdictions require stormwater to receive some level of treatment before being discharged directly into waterways. Examples of treatment processes used for stormwater include retention basins, wetlands, buried vaults with various kinds of media filters, and vortex separators (to remove coarse solids).
Sewage treatment is done in three stages: primary, secondary and tertiary treatment (Figure 1).
In primary treatment, sewage is stored in a basin where solids (sludge) can settle to the bottom and oil and lighter substances can rise to the top. These layers are then removed and then the remaining liquid can be sent to secondary treatment. Sewage sludge is treated in a separate process called sludge digestion.
Secondary treatment removes dissolved and suspended biological matter, often using microorganisms in a controlled environment. Most secondary treatment systems use aerobic bacteria, which consume the organic components of the sewage (sugar, fat, and so on). Some systems use fixed film systems, where the bacteria grow on filters, and the water passes through them. Suspended growth systems use “activated” sludge, where decomposing bacteria are mixed directly into the sewage. Because oxygen is critical to bacterial growth, the sewage is often mixed with air to facilitate decomposition.
Tertiary treatment (sometimes called “effluent polishing”) is used to further clean water when it is being discharged into a sensitive ecosystem. Several methods can be used to further disinfect sewage beyond primary and secondary treatment. Sand filtration, where water is passed through a sand filter, can be used to remove particulate matter. Wastewater may still have high levels of nutrients such as nitrogen and phosphorus. These can disrupt the nutrient balance of aquatic ecosystems and cause algae blooms and excessive weed growth. Phosphorus can be removed biologically in a process called enhanced biological phosphorus removal. In this process, specific bacteria, called polyphosphate accumulate organisms that store phosphate in their tissue. When the biomass accumulated in these bacteria is separated from the treated water, these biosolids have a high fertilizer value. Nitrogen can also be removed using nitrifying bacteria. Lagooning is another method for removing nutrients and waste from sewage. Water is stored in a lagoon and native plants, bacteria, algae, and small zooplankton filter nutrients and small particles from the water.
Sludge Digestion & Disposal
Sewage sludge scraped off the bottom of the settling tank during primary treatment is treated separately from wastewater. Sludge can be disposed of in several ways. First, it can be digested using bacteria; bacterial digestion can sometimes produce methane biogas, which can be used to generate electricity. Sludge can also be incinerated, or condensed, heated to disinfect it, and reused as fertilizer.
When a liquid sludge is produced, further treatment may be required to make it suitable for final disposal. Sewage sludge scraped off the bottom of the settling tank during primary treatment is treated separately from wastewater. Sludge can be disposed of in several ways. First, it can be digested using bacteria; bacterial digestion can sometimes produce methane biogas, which can be used to generate electricity. Sludge can also be incinerated, or condensed, heated to disinfect it, and reused as fertilizer.
Typically, sludges are thickened (dewatered) to reduce the volumes transported off-site for disposal. There is no process which completely eliminates the need to dispose of biosolids. There is, however, an additional step some cities are taking to superheat sludge and convert it into small pelletized granules that are high in nitrogen and other organic materials. In New York City, for example, several sewage treatment plants have dewatering facilities that use large centrifuges along with the addition of chemicals such as polymer to further remove liquid from the sludge. The removed fluid, called “centrate,” is typically reintroduced into the wastewater process. The product which is left is called “cake,” and that is picked up by companies which turn it into fertilizer pellets. This product is then sold to local farmers and turf farms as a soil amendment or fertilizer, reducing the amount of space required to dispose of sludge in landfills. Much sludge originating from commercial or industrial areas is contaminated with toxic materials that are released into the sewers from the industrial processes. Elevated concentrations of such materials may make the sludge unsuitable for agricultural use and it may then have to be incinerated or disposed of to landfill.
Notably, throughout the development of excreta, wastewater, wastewater sludge and biosolids management – from the least developed to the most developed countries – there are inevitable public concerns about how best to manage this “waste” that is also a resource. Putting biosolids to their best uses in each local situation is the goal of most of the programs discussed in the following reports. That is the goal of many sanitation and water quality experts. But the general public has other goals: avoiding the waste and the odors it can produce.There is a natural aversion to fecal matter and anything associated with it. Conflicts arise when experts propose recycling this “waste,” usually in a treated and tested form commonly called “biosolids,” back to soils in communities.
Managing excreta and wastewater sludge to produce recyclable biosolids involves many technical challenges. But equally significant are these social, cultural, and political challenges. Funding is required to build infrastructure – and, around the world, the public is the source of funding, either through taxes or sewer usage fees. In order for proper sanitation to be built and operated, complex community sanitation agencies with support from state, provincial, and national governments are needed.
Wastewater quality indicators are laboratory tests to assess suitability of wastewater for disposal or re-use. Tests selected and desired test results vary with the intended use or discharge location. Tests measure physical, chemical, and biological characteristics of the wastewater.
Aquatic organisms cannot survive outside of specific temperature ranges. Irrigation runoff and water cooling of power stations may elevate temperatures above the acceptable range for some species. Temperature may be measured with a calibrated thermometer.
Solid material in wastewater may be dissolved, suspended, or settleable. Total dissolved solids or TDS (sometimes called filtrable residue) is measured as the mass of residue remaining when a measured volume of filtered water is evaporated. The mass of dried solids remaining on the filter is called total suspended solids (TSS) or nonfiltrable residue. Settleable solids are measured as the visible volume accumulated at the bottom of an Imhoff cone after water has settled for one hour. Turbidity is a measure of the light scattering ability of suspended matter in the water. Salinity measures water density or conductivity changes caused by dissolved materials.
Virtually any chemical may be found in water, but routine testing is commonly limited to a few chemical elements of unique significance.
Water ionizes into hydronium (H3O) cations and hydroxyl (OH) anions. The concentration of ionized hydrogen (as protonated water) is expressed as pH.
Most aquatic habitats are occupied by fish or other animals requiring certain minimum dissolved oxygen concentrations to survive. Dissolved oxygen concentrations may be measured directly in wastewater, but the amount of oxygen potentially required by other chemicals in the wastewater is termed an oxygen demand. Dissolved or suspended oxidizable organic material in wastewater will be used as a food source. Finely divided material is readily available to microorganisms whose populations will increase to digest the amount of food available. Digestion of this food requires oxygen, so the oxygen content of the water will ultimately be decreased by the amount required to digest the dissolved or suspended food. Oxygen concentrations may fall below the minimum required by aquatic animals if the rate of oxygen utilization exceeds replacement by atmospheric oxygen.
The reaction for biochemical oxidation may be written as:
Oxidizable material + bacteria + nutrient + O2 → CO2 + H2O + oxidized inorganics such as NO3 or SO4
Oxygen consumption by reducing chemicals such as sulfides and nitrites is typified as follows:
S– + 2 O2 → SO4–
NO2- + ½ O2 → NO3-
Since all natural waterways contain bacteria and nutrient, almost any waste compounds introduced into such waterways will initiate biochemical reactions (such as shown above). Those biochemical reactions create what is measured in the laboratory as the biochemical oxygen demand (BOD).
Oxidizable chemicals (such as reducing chemicals) introduced into a natural water will similarly initiate chemical reactions (such as shown above). Those chemical reactions create what is measured in the laboratory as the chemical oxygen demand (COD).
Both the BOD and COD tests are a measure of the relative oxygen-depletion effect of a waste contaminant. Both have been widely adopted as a measure of pollution effect. The BOD test measures the oxygen demand of biodegradable pollutants whereas the COD test measures the oxygen demand of biogradable pollutants plus the oxygen demand of non-biodegradable oxidizable pollutants.
The so-called 5-day BOD measures the amount of oxygen consumed by biochemical oxidation of waste contaminants in a 5-day period. The total amount of oxygen consumed when the biochemical reaction is allowed to proceed to completion is called the Ultimate BOD. The Ultimate BOD is too time consuming, so the 5-day BOD has almost universally been adopted as a measure of relative pollution effect.
There are also many different COD tests. Perhaps, the most common is the 4-hour COD.
There is no generalized correlation between the 5-day BOD and the Ultimate BOD. Likewise, there is no generalized correlation between BOD and COD. It is possible to develop such correlations for a specific waste contaminant in a specific wastewater stream, but such correlations cannot be generalized for use with any other waste contaminants or wastewater streams.
The laboratory test procedures for the determining the above oxygen demands are detailed in the following sections of the “Standard Methods For the Examination Of Water and Wastewater” available at www.standardmethods.org:
5-day BOD and Ultimate BOD: Sections 5210B and 5210C
COD: Section 5220
Nitrogen is an important nutrient for plant and animal growth. Atmospheric nitrogen is less biologically available than dissolved nitrogen in the form of ammonia and nitrates. Availability of dissolved nitrogen may contribute to algal blooms. Ammonia and organic forms of nitrogen are often measured as Total Kjeldahl Nitrogen, and analysis for inorganic forms of nitrogen may be performed for more accurate estimates of total nitrogen content.
Chlorine has been widely used for bleaching, as a disinfectant, and for biofouling prevention in water cooling systems. Remaining concentrations of oxidizing hypochlorous acid and hypochlorite ions may be measured as chlorine residual to estimate effectiveness of disinfection or to demonstrate safety for discharge to aquatic ecosystems.
Water may be tested by a bioassay comparing survival of an aquatic test species in the wastewater in comparison to water from some other source. Water may also be evaluated to determine the approximate biological population of the wastewater. Pathogenic micro-organisms using water as a means of moving from one host to another may be present in sewage. Coliform index measures the population of an organism commonly found in the intestines of warm-blooded animals as an indicator of the possible presence of other intestinal pathogens.
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Electrical Conductivity Testing Applied to the Assessment of Freshly Collected Kielmeyera coriacea Mart. Seeds: MyronLMeters.com
Tweet MyronLMeters.com brings you the latest in conductivity measurement research like the article below. Please click here for accurate, reliable, conductivity meters. Abstract Assessment of seed vigor has long been an important tool of seed quality control programs. The conductivity test is a promising method for assessment of seed vigor, but proper protocols for its […]
MyronLMeters.com brings you the latest in conductivity measurement research like the article below. Please click here for accurate, reliable, conductivity meters.
Assessment of seed vigor has long been an important tool of seed quality control programs. The conductivity test is a promising method for assessment of seed vigor, but proper protocols for its execution have yet to be established. The objective of this study was to assess the efficiency of electrical conductivity (EC) testing as a means of assessing the viability of freshly collected Kielmeyera Coriacea Mart. seeds. The test was performed on individual seeds rather than in a bulk configuration. Seeds were soaked for different periods (30 min, 90 min, 120 min., 180 min, and 240 min) at a constant temperature of 25°C. Conductivity was then measured with a benchtop EC meter.
Seeds are the primary factor of the seedling production process, despite their minor contribution to the end cost of each seedling. In order to estimate the success rate of seedling production, it is essential that seed characteristics such as vigor and germinability be known .
The importance of knowing the characteristics of Brazilian forest species to safer and more objective management of seedling production cannot be overstated. However, such studies are scarce, particularly in light of the vast number of species with this potential . Given the intensity of anthropogenic pressure and the importance of rehabilitating disrupted or degraded environments, in-depth research of forest species is warranted.
Routine methods used for determination of seed quality and viability include germination testing and the tetrazolium test. Methods such as measurement of soak solution pH, electrical conductivity, and potassium content of leachate, all based on the permeability of the cell membrane system, are increasingly being employed in the assessment of seed vigor, as they are reliable and fast and can thus speed the decision making process.
Electrical conductivity testing, as applied to forest seeds, has yet to be standardized. Studies conducted thus far have focused on assessment of seed soaking times, which may range from 4 to 48 hours. Even at 48 hours, the conductivity test is considered a rapid technique as compared to the germination test, which, despite its status as a widespread and firmly established method, can take anywhere from 30 to 360 days to yield results (depending on species), and is limited by factors such as dormant seeds.
The total concentration of electrolytes leached by seeds during soaking has long been assessed indirectly, mostly through the conductivity test, which takes advantage of the fact that inorganic ions make up a substantial portion of these electrolytes [3–5].
Rapid assessment of seed quality allows for preemptive decision-making during harvest, processing, sale and storage operations, thus optimizing use of financial resources throughout these processes.
K. coriacea Mart. is a species of the Clusiaceae (Guttiferae) family popularly known in Brazil as pau-santo (Portuguese for “holy wood”), due to its properties as a medicinal and melliferous plant and as a source of cork. In traditional Brazilian medicine, the leaves are used as an emollient and antitumor agent, and the resin as a tonic and in the treatment of toothache and various infections. The fruits are used in regional crafts and flower arrangements. Even if the dye is of the leaves and bark. The trunk provides cork .
K. coriaceae specimens grow to approximately 4 meters in height. The flowering period extends from January to April and the fruiting period from May to September, and seed collection can take place from September onwards. Leaves are alternate, simple, oval to elliptical, coriaceous, and clustered at the end of the branches, and feature highly visible, pink midribs. A white to off-white latex is secreted in small amounts upon removal of leaves. Flowers are white to pale pink in color, large, fragrant, with many yellow stamens and are borne in short clusters near the apex of the branches. Seedling production requires that seeds be sown shortly after collection.
In the fruit are found 60 to 80 seeds with anemochoric. The seed varies from round to oblong, winged at the ends, light brown color, has integument thin and fragile, with smooth texture, the sizes range from 4.3 to 5.6 cm long, 1.3 to 1.9 cm wide, and 0.2 to 0.5 centimeter thick. The individual weight of the seeds ranges from. 112 to.128 grams. Nursery radicle emission occurred at 7 days and the germination rate was 90%. Germination occurs within 7 to 10 days. The species is slow growing, both in the field and in a nursery setting .
The present study sought to assess the applicability of the conductivity test to freshly collected K. coriacea Mart. seeds by determining the optimal soak time for performance of the test and comparing results obtained with this method against those obtained by tetrazolium and germination testing of seeds from the same batch.
2. Materials and Methods
2.1. Seed Collection
Seeds were collected in the cerrado sensu stricto, in SCA (Clean Water Farm), area of study at the University of Brasília (UNB) in August 2010, matrixes marked with the aid of GPS, after the period of physiological maturation of the seeds. The collection of fruits was directly from the tree, with the help of trimmer, then the seeds were processed and stored in paper bags at room temperature in the laboratory.
2.2. Conductivity Test
The development of tests to evaluate the physiological quality of seeds, as well as the standardization of these is essential for the establishment of an efficient quality control . One of the main requirements for the seed vigor refers to obtain reliable results in a relatively short period of time, allowing the speed of decision making especially as regards the operations of collection, processing, and marketing . The literature indicates that rapid tests are most studied early events related to the deterioration of the sequence proposed by Delouche and Baskin  as the degradation of cell membranes and reduced activity, and biosynthetic respiratory . The measurement of electrical conductivity through the electrolyte amount released by soaking seeds in water has been applied by the individual method where each seed is a sample or more often, a sample of seed representative of a population (mass method). For this case, the results represent the average conductivity of a group of seeds, may a small amount of dead seeds affect the conductivity of a batch with many high-quality seed generating a read underestimated. To minimize this problem, we recommend choosing the seeds, excluding the damaged seeds.
The electrical conductivity is based on the principle that the deterioration process is the leaching of the cells of seeds soaked in water due to loss of integrity of cellular systems. Thus, low conductivity means a high-quality seed and high conductivity, that is, greater output seed leachate, suggests that less force .
The electrical conductivity is not yet widely used in Brazil, its use is restricted to activities related to research (Krzyzanowski et al., 1991). There are common jobs using this test to determine the physiological quality of tree seeds. However, it is a promising vigor test for possible standardization of the methodology, at least within a species. However, it is a promising vigor test for possible standardization of the methodology, at least within a species. However, there are factors which influence the conductivity values as the size, the initial water content, temperature and time of soaking, the number of seeds per sample, and genotype .
Five treatments were carried out to test the efficiency of the conductivity test as a means of evaluating the viability of freshly collected K. coriacea Mart. seeds.
Five runs of 20 seeds were tested for each treatment. Seeds were individually placed into containers holding 50 mL of distilled water and left to soak for 30, 90, 120, 180, and 240 minutes in a germination chamber set to a constant temperature of 25°C. The minimum time taken for the soaking of 30 minutes was adopted by the same authors and Amaral and peske , Fernandes et al. , and Matos  who concluded that the period of 30 minutes of soaking is more effective to estimate the germination of the seeds. After each period, the conductivity of the soak solution was immediately tested with a benchtop EC meter precise to +/−1% (Quimis). Readings were expressed as μS·cm−1/g−1 seed .
Data thus obtained were subjected to analysis of variance with partitioning into orthogonal polynomials for analysis of the effect of soaking times on electrical conductivity.
2.3. Tetrazolium Test
The tetrazolium test, also known as biochemical test for vitality, is a technique used to estimate the viability and seed germination. A fundamental condition for ensuring the efficiency of the test is the direct contact of the tetrazolium solution with the tissues of the seed to be tested. Due to the impermeability of the coats of most forest tree seeds, it is necessary to adopt a previous preparation of the seeds that were tested. This preparation is based on facilitating entry of the solution in the seed. Among the preparations that precede the test we have cutting the seed coat, seed coat removal, scarification by sandpaper scarification by soaking in hot water and water . In the previous preparation of the seeds, factors such as concentration of the solution or even the time of the staining solution can affect the efficiency of the test in the evaluation of seed quality. The time required for the development of appropriate color according to the Rules for Seed Analysis  varies depending on each species, can be between 30 and 240 minutes.
The tetrazolium test has been widely used in seeds of various species due to the speed and efficiency in the characterization of the viability and vigor, and the possibility of damage to the same distinction, assisting in the process of quality control from the steps of harvest storage (GRIS et al, 2007).
The tetrazolium test was also applied to freshly collected K. coriacea Mart. seeds, for a total of three runs and 20 seeds. Seeds were soaked in a 0.5% solution of 2,3,5-triphenyl-2H-tetrazolium for 24 hours in a germination chamber set to a constant temperature of 25°C. After each run, seeds were washed, bisected, and the half-containing the embryonic axis placed under a stereo viewer for examination of staining patterns .
2.4. Germination Test
The standard germination test is the official procedure to evaluate the ability of seeds to produce normal seedlings under favorable conditions in the field, but does not always reveal differences in quality and performance among seed lots, which can manifest in storage or in the field .
During the germination test optimum conditions are provided and controlled for seeds to encourage the resumption of metabolic activity which will result in the seedlings. The main objective of the germination test is the information about the quality of seeds, which is used in the identification of lots for storage and sowing .
Freshly collected K. coriacea Mart. seeds were placed in a germination chamber at a constant temperature of 25°C (Treatment 1) or an alternating temperature of 20–30°C (Treatment 2), on a standard cycle of 8 hours of light and 16 hours of dark. Each test consisted of five runs and was performed on 20 seeds.
Germination was defined as emergence of at least 2.0 mm of the primary root . Assessment was conducted daily, and emergence was observed between day 6 and day 7. At the end of the 14-day test period, the germination percentage was calculated on the basis of radicle emergence .
3.1. Conductivity Test
Different soaking times were not associated with any significant differences in conductivity results in K. coriacea Mart. seeds (Table 1).
Table 1: Conductivity ranges of freshly collected Kielmeyera coriacea Mart. seeds after soaking for different periods.
Seeds with a leachate conductivity range of 7–17.99 μS·cm·g were considered nonviable, confirming the hypothesis behind conductivity testing, which is the nonviable seeds that have higher soaking solution conductivity values (Table 2).
Table 2: Percentage of viable Kielmeyera coriacea Mart. seeds according to EC range.
Analysis of variance revealed a low coefficient of variation (20.26%), which suggests good experimental control (Table 3).
Table 3: Analysis of variance of various soaking times for electrical conductivity testing of Kielmeyera coriacea Mart. seeds.
After analysis of variance, the correlation between the soaking time and electrical conductivity variables was assessed. The cubic model yielded
which is indicative of a positive correlation between the study variables.
The following equation was obtained on the basis of the cubic model:
Analysis of a plot of the above function in the GeoGebra 2007 software package shows that variation in electrical conductivity as a function of soaking time is minor and approaches a constant, which is consistent with the study results, in which changes in soaking time had no influence on conductivity (Figure 1).
Matos  reported that a 30-minute soak was enough for assessment of Anadenanthera falcata, Copaifera langsdorffii, and Enterolobium contortisiliquum seeds by the soaking solution pH method—that is, the amount of matter leached after this period sufficed for measurement.
Although the principle of conductivity is the same used for the test pH of exudate, the soaking time needed to analyze the differential seeds through the conductivity may be explained by the fact that this technique is quantitative, while pH in the art exudate analyzes are qualitative. In other words to the technique of pH values of the exudate it is important to detect the acidity of imbibition while on the electrical conductivity we draw a comparison between the analyzed values to separate viable from nonviable samples. To determine a value of electrical conductivity as a reference to determine viable seeds are to be considered the values obtained for fresh seeds and seeds stored.
The thickness of the K. coriacea Mart. seed coat may also have affected the soaking procedure; this species has very thin seed coats, which makes soaking a very fast process.
These results are consistent with those reported by Rodrigues , who subjected stored K. coriaceaMart. seeds to the conductivity test and found that 90 minutes is an appropriate soaking time for analysis.
Therefore, it can be inferred that for seed Kielmeyera coriacea Mart. the soaking time of 90 minutes can be applied to obtain satisfactory results.
3.2. Tetrazolium Test
Table 4 shows the results of tetrazolium testing of K. coriacea Mart. seeds in our sample. The mean viability rate was 96.6%. The testing procedure was based on Brazilian Ministry of Agriculture recommendations .
The results of the tetrazolium test were quite similar to those obtained with the conductivity method, thus confirming the efficiency of the latter method as a means for assessing the viability of K. coriaceaMart. seeds.
3.3. Germination Test
The germination test results of freshly collected K. coriacea Mart. seeds are shown in Table 5. Regardless of temperature, both test batches exhibited good viability, and no seed dormancy was detected.
Radicle emergence was observed between day 7 and day 9 of the test, according to the analysis criteria proposed by Labouriau .
These findings are consistent with those of Melo et al.,  who reported high and relatively rapid germination rates for K. coriacea seeds kept at 25°C on paper towels, with emergence of a perfect radicle on the 7th day of assessment.
The electrical conductivity can be used as an indicator of seed viability and presents two advantages: to provide rapid and reliable results and the technique is not destructive and can use the seeds after the conductivity test, so they can be used to produce seedlings.
The present study showed that different soaking times had no effect on the results of conductivity testing of freshly collected K. coriacea Mart. seeds, suggesting that the amount of leached matter was never below the threshold required for adequate testing.
Electrical conductivity testing proved to be a feasible option for viability testing of K. coriacea Mart. seeds, as the results obtained with conductivity testing were confirmed by germination testing and by the tetrazolium test.
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- L. L. Rodrigues, Study of imbibition time for application the method of electrical conductivity in the verification of the feasibility forest seeds stored, monograph, University of Brasília, Brasília, Brazil, 2010.
- J. T. Melo, J. F. Ribeiro, and V. L. G. F. Lima, “Germination of Seeds of some tree species native to the Cerrado,” Journal of Seeds, vol. 1, no. 2, pp. 8–12, 1979.
1Seed Technology Laboratory of Forestry, Department of Forestry, University of Brasilia, CP 04357, 70919970 Campus Asa Norte, DF, Brazil
2Department of Forestry, University of Brasilia, CP 04357, 70919970 Campus Asa Norte, DF, Brazil
Received 17 December 2011; Accepted 14 February 2012
Academic Editors: A. Berville, C. Gisbert, J. Hatfield, and Y. Ito
Copyright © 2012 Kennya Mara Oliveira Ramos et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Peat Water Treatment Using Combination of Cationic Surfactant Modified Zeolite, Granular Activated Carbon, and Limestone
Tweet MyronLMeters.com attempts to provide its customers with the latest in water quality research and industry updates. Find more at https://www.myronlmeters.com/. Abstract This research was conducted essentially to treat fresh peat water using a series of adsorbents. Initially, the characterization of peat water was determined and five parameters, including pH, colour, COD, turbidity, and iron ion […]
MyronLMeters.com attempts to provide its customers with the latest in water quality research and industry updates. Find more at https://www.myronlmeters.com/.
This research was conducted essentially to treat fresh peat water using a series of adsorbents. Initially, the characterization of peat water was determined and five parameters, including pH, colour, COD, turbidity, and iron ion exhibited values that exceeded the water standard limit. There were two factors influencing the adsorption capacity such as pH, and adsorbent dosages that were observed in the batch study. The results obtained indicated that the majority of the adsorbents were very efficient in removing colour, COD, turbidity at pH range 2-4 and Fe at pH range 6-8. The optimum dosage of cationic surfactant modified zeolite (CSMZ) was found around 2 g while granular activated carbon (GAC) was exhibited at 2.5 g. In column study, serial sequence of CSMZ, GAC, and limestone showed that the optimal reduction on the 48 hours treatment were found pH = 7.78, colour = 12 TCU, turbidity = 0.23 NTU, COD = 0 mg/L, and Fe= 0.11 mg/L. Freundlich isotherm model was obtained for the best description on the adsorption mechanisms of all adsorbents.
Keywords: cationic surfactant modified zeolite, granular activated carbon, limestone, peat water
Water is essential and fundamental to all living forms and is spread over 70.9% of the earth’s surface. However, only 3% of the earth’s water is found as freshwater, of which 97% is in ice caps, glaciers and ground water (Bhatmagar & Minocha, 2006). In Malaysia, more than 90% of fresh water supply comes from rivers and streams. The demand for residential and industrial water supply has grown rapidly coupled with an increase in population and urban growth (WWF Malaysia, 2004). Water demand in affected populations such as rural areas also demands that attention is paid to providing more sustainable solutions rather than transporting bottled water (Loo et al., 2012). For this reason, it is essential to ensure availability of local sources of water supply and even develop new potential sources of water such as from peat swamp forest to overcome future water shortages.
River water surrounded by peat swamp forest is defined as peat water and is commonly available as freshwater since it has a low concentration of salinity. The previous study shows that peat swamp forest has high levels of acidity and organic material depending on its region and vegetation types (Huling et al., 2001). Under natural conditions, tropical peat lands serve as reservoirs of fresh water, moderate water levels, reduce storm-flow and maintain river flows, even in the dry season, and they buffer against saltwater intrusion (Wosten et al., 2008).
Due to the acidity and high concentration of organic material, selective treatment of peat water must be conducted prior to its use as water supply. Recently, many methods have been designed and have proven their effectiveness in treating raw water such as coagulation and flocculation (Franceschi et al., 2002; Liu et al., 2011; Syafalni et al., 2012a), absorption (Ćurković et al., 1997), filtration (Paune et al., 1998) and combining (Hidaka et al., 2003). Careful consideration of the most suitable method is important to ensure that the adsorption process is the most beneficial, economically feasible method as well as easy to operate for producing high quality of water in a particular location.
Many researchers have shown that activated carbon is an effective adsorbent for treating water with high concentrations of organic compounds (Eltekova et al., 2000; Syafalni et al., 2012b). Its usefulness derives mainly from its large micropore and mesopore volumes and the resulting high surface area (Fu & Wang, 2011). However, its high initial cost makes it less economically viable as an adsorbent. Low cost adsorbent such as zeolite nowadays has been explored for its ability in many fields especially in water treatment. Natural zeolite has negative surface charge which gives advantages in absorbing unwanted positive ions in water such heavy metal. These ions and water molecules can move within the large cavities allowing ionic exchange and reversible rehydration (Jamil et al., 2010). The effectiveness of zeolite has been improvised by modified zeolite with surfactant in order to achieve higher performance in removing organic matter (Li & Bowman, 2001). Among tested cationic surfactants, hexa-decyl-tri-methyl ammonium (HDTMA) ions adsorbed onto adsorbent surfaces are particularly useful for altering the surface charge from negative to positive (Chao & Chen, 2012). Surfactant modified zeolite has been shown to be an effective adsorbent for multiple types of contaminants (Zhaohu et al., 1999).
Zeolite is modified to improve its capability of exchanging the anion by cationic surfactants, called CSMZ. CSMZ adsorbs all major classes of water contaminants (anions, cations, organics and pathogens), thus making it reliable for a variety of water treatment applications (Bowman, 2003). Nowadays, interest in the adsorption of anions and neutral molecules by surfactant modified zeolite has increased (Zhang et al., 2002). Modification of zeolite by surfactant is commonly done by cationic or amphoteric surfactants. By introducing surfactant to the zeolite, an organic layer is developed on the external surfaces and the charge is reversed to positive (Li et al., 1998). However, the present study used zeolite that had been modified using Uniquat (QAC-50) as cationic surfactant (CSMZ) and their performance towards the removal of color, COD, turbidity and iron ion from peat water were investigated.
Four adsorbents were used in these experiments which are natural zeolite, zeolite modified by cationic surfactant, activated carbon and limestone. All adsorbents were prepared with equivalent sizes of 1.18 mm – 2.00 mm. Hydrochloric acid (HCl) and sodium hydroxide (NaOH) were used for polishing zeolite during the preparation phase and for pH adjustment of the sample. Furthermore, potassium dichromate (K2CrO7), silver sulphate (Ag2SO4), sulphuric acid (H2SO4) and mercury (II) sulphate (HgSO4) were used as digestion solution reagents and acid reagents for COD analysis. Lastly, Uniquat (QAC-50) was used as cationic surfactant to modify the zeolite.
2.1 Preparation of Surfactant Modified Zeolite
In these studies, 100 g of prewashed natural zeolite was contacted with 5.6 ml/l Uniquat (QAC-50) as cationic surfactant (CSMZ). The mixture was then stirred at room temperature for 4 hours at 300 rpm (Karadag et al., 2007). The zeolite then was filtered and washed with distilled water several times. After that, the absorbent was dried in an oven at a temperature of 105 °C for 15 hours.
2.2 est Procedures
2.2.1 Batch Studies
Serial batch studies were conducted at room temperature (28 ± 1 °C) to investigate the influence of pH and dosage for removing colour, COD, turbidity and iron ion from peat water. Shaking speed of 200 rpm for 20 minutes were fixed and operated respectively. A working volume of 150ml peat water sample was set up in 250 ml conical flasks. Preceding the batch studies, initial concentration for those parameters was determined. The optimum pH and dosage of absorbent were determined. Subsequently, the percentage of removal was finally determined, plotted, and compared.
2.2.2 Batch Column Studies
Column studies were carried out using a plastic column with dimensions: 5.4 cm diameter and 48 cm length. Three adsorbents were filled inside the column at a specific depth with the supporting layers of marbles, cotton wool, and perforated net. Total volume of 2000 ml peat water was pumped in the up flow mode from the vessel into the column by using a Masterflex peristaltic pump at a minimum flow rate of (30, 60, 90) ml/min. In this study, however, column studies were performed un-continuously (batch) due to limitations of time. All parameters related to the column design are summarized in the following Table 1.
Table 1. Column studies parameters
|Horizontal Surface Area, A||cm2||
|Column volume, V||cm3||1099.3|
|Flowrate, Q||ml/min||30, 60, 90|
|Surface Loading Rate, SLR= Q/A||cm/min||1.31, 2.62, 3.93|
The serial sequence arrangements of adsorbents were conducted as shown in Figure 1 below. Effluent samples were collected at various time intervals, whilst maintaining room temperature, and analysed.
Figure 1. Schematic diagrams of lab-scale column studies
3. Results and Discussion
3.1 eat Water Characterization
Surface water originating from the peat swamp forest was taken from Beriah peat swamp river along the Kerian River on several occasions as the main sample. The characterization of peat water was carried out at the sampling point (in-situ measurement) using a multi-parameter probe as well as in the environmental laboratory of civil engineering, USM. Fundamentally, the characterization procedures were based on the Standard Methods for the Examination of Water and Wastewater (APHA, 1992). Table 2 represents the peat water characteristics in average value and the comparison to the standard drinking water quality in Malaysia.
Table 2. The characteristics of peat water sample from Beriah Peat Swamp Forest
|4.67 – 4.98|
Thirteen parameters were successfully determined where the first six parameters, including pH, temperature, TDS, DO, conductivity, and salinity were measured at the sampling point, whilst the rest of the parameters, including colour, turbidity, COD, iron ion, Ammoniacal Nitrogen, NH3-N, Ammonia (NH3), and Ammonium (NH4+) were examined from the sample brought to the environmental laboratory on the same day.
Acidic pH of the peat water was predicted due to the composition of the surrounding peat soil itself which had been formed by decaying material possessing humic substances (Rieley, 1992). Besides that, humic substances also lead to the high organic content as humic substances are comprised of numerous oxygen containing functional group and fractions (humic acid, fulvic acids and humin) with different molecular weights which mean yielding high concentration of turbidity and COD as well as coloured water (Torresday et al., 1996). Moreover, composition of peat soil may also have an impact on the iron ion concentration of peat water (Botero et al., 2010).
From the thirteen parameters, five parameters were indicated exceeding the standard limit. These parameters were pH, colour, turbidity, COD, and iron ion that showed values of 4.67 – 4.98, 224.7 TCU, 20.8 NTU, 33.3 mg/l, and
1.24 mg/l respectively while the standard limit of these parameters are 6.5 – 9.0, 15 TCU, 5 NTU, 10 mg/l, and 0.3 mg/l accordingly.
3.2 Effect of Initial pH on the Efficiency of Colour, COD, Turbidity, and Iron Ion (Fe) Removal
Influence of initial pH on the adsorption capacity for removing colour, COD, turbidity, and iron ion were investigated.
Figure 2(a) to Figure 2(d) below, displayed the percentage removal of colour, COD, turbidity, and iron ion against pH of adsorbents respectively.
Figure 2(a) shows the maximum removal percentage of colour that was removed by natural zeolite, CSMZ, and granular activated carbon (GAC) which were 79%, 90%, 82% respectively. This adsorption is depended on the characteristic of adsorbents itself. For zeolite and CSMZ were related to the amount of cationic ions (Al3+) increased, resulting in high reaction activity and GAC was related to the adsorption capacity. It was observed that the adsorption capacity was highly dependent on the pH of the solution, and indicated that the colour removal efficiencies decreased with the increase of solution pH.
The pH of the system exerts profound influence on the adsorptive uptake of adsorbate molecules presumably due to its influence on the surface properties of the adsorbent and ionization or dissociation of the adsorbate molecule. Figure 2(b) represents the percentage removal of natural zeolite and CSMZ where they reach optimum efficiency in removing organic compound (COD) at pH 2 with efficiency of 53% and 60% respectively. Meanwhile, the highest percentage removal of COD for GAC was achieved at pH 4 with efficiency obtained about 61%. Identical trends in colour removal were exhibited in percentage removal of COD for natural zeolite, CSMZ and GAC. In fact, this result also reveals that GAC has the highest percentage removal among natural zeolite and CSMZ yet optimum in difference pH solution. Neutralization mechanism occurs in low pH makes color removal, COD removal and Turbidity removals at pH 2 are higher for most of absorbents in this process.
In Figure 2(c), percentage turbidity removal against pH for each adsorbent revealed that optimal reduction of turbidity was obtained in an acidic environment with efficiency removal of 96%, 98%, 95% for natural zeolite, CSMZ, and GAC respectively. When the pH of the solution was adjusted above pH 6 to pH 12, the tendencies of all adsorption performances were gradually decreased. Moreover, it also showed that the lowest efficiency for the three adsorbents were identified at pH 12 with percentage values removal 55%, 61%, and 59% for natural zeolite, CSMZ, and GAC respectively.
Figure 2(d) demonstrates the removal efficiencies of iron ion as a function of the influent pH. The maximum removal of iron ion was observed at pH 8 for both natural zeolite and CSMZ whereas GAC had its optimum removal at pH 6. Natural zeolite and CSMZ only yielded 73% and 62% removal efficiency while GAC had more significant removal with removal efficiency of 80% to the iron ion concentration. Further, it is evident from the graph that gradual increment of removal efficiency for natural zeolite, CSMZ, and GAC occurred when the initial pH of the solution was increased to higher values. Somehow, at pH values greater than 6 the removal efficiency of GAC reduced slightly while for natural zeolite and CSMZ the reduction occurred from pH values above 8.
3.3 Effect of Adsorbent Dosage on the Efficiency of Colour, COD, Turbidity, and Iron Ion (Fe) Removal
The effect of adsorbent dosage was studied for all adsorbents employed on colour, COD, turbidity, and iron ion removal by varying the dosage of adsorbent and keeping all other experimental conditions constant. The pH was set to acidic conditions which were most favourable in obtaining the highest removal efficiency. In this study, to find optimal adsorbent dosage of natural zeolite and CSMZ, the appropriate experiments were carried out at adsorbent dosages in the range of 0.5 g to 5.0 g while for GAC, the adsorbent dosage was varied from 0.01 g to 4.0
- The experimental results for all the adsorbents are represented by Figure 3(a) to Figure 4(d).
Figure 3. Percentage of color (a), COD (b), turbidity (c), and Fe (d) removal against pH for NZ, and CSMZ
Figure 3(a) displays the relationship between the amount of adsorbent mass (dosage) and adsorption efficiency for natural zeolite and CSMZ in terms of removing colour. The colour removal of peat water increased from about 25% to 52% with increasing adsorbent dosage of natural zeolite from 0.5 g to 3.5 g whereas for CSMZ, removal percentage increased from 41% to 53% with increasing adsorbent dosage from 0.5 g to 2.0 g. However, further increase in adsorbent dosage to 5.0 g only led to slight degradation of removal efficiency to 50% and 41% for natural zeolite and CSMZ respectively. This degradation with further increases in adsorbent dosage was due to the unsaturated adsorption active sites during the adsorption process since the adsorbates in the vessel were only shaken for 20 minutes (insufficient time). Besides, modification of zeolite by cationic surfactant had proven to have better colour removal as presented in the graph.
Percentage removal of COD against the adsorbent dosage is shown in Figure 3(b). It was observed that the highest percentage removal for both natural zeolite and CSMZ to remove COD were 51% and 59%, achieved at adsorbent dosage 3.5 g and 2.0 g respectively.
The variations in removal of turbidity of peat water at various system pH are shown in Figure 3(c). The removal rate of turbidity was highest at the adsorbent dosage of 0.5 g with 70% and 93% removal efficiency for respective natural zeolite and CSMZ. The removal rate showed a smooth downward trend with the increase in adsorbent dosage. Concurrently, the adsorption capacity gradually decreased with the increasing adsorbent dosage. The least efficient removal of turbidity was noted at dosage 5.0 g with percentage removal recorded for natural zeolite and CSMZ only 57% and 70% respectively.
Figure 3(d) demonstrates the percentage iron ion removal of natural zeolite and CSMZ with respect to their dosage. The result shows that there was a significant difference trend in iron ion adsorption efficiencies between natural zeolite and CSMZ. For natural zeolite, it was shown that the removal percentage of iron ion had increased until it reached 1.0g of dosage with 72% of removal efficiency. On the other hands, CSMZ was only able to remove about 63% of iron ion when its dosage was increased to 2.5 g. The lowest percentage removals were 47% and 57% recognized at the adsorbent dosage 5.0 g for respective natural zeolite and CSMZ.
Figure 4. Percentage of color (a), COD (b), turbidity (c), and Fe (d) removal against dosage for GAC
The result illustrated in Figure 4(a) shows the maximum removal percentage of colour for GAC at 2.5 g dosage was 62%. Moderate increment in colour removal was identified along with the addition dosage of 2.5 g whilst abatement of removal efficiency began subsequently at adsorbent dosage of 3.0 g to 4.0 g.
The results from Figure 4(b) indicated that increasing the GAC dosage would increase the efficiency in removing COD respectively. The optimum dosage was recorded at 3.0 g with 72% of removal efficiency. Meanwhile, increasing the dosage above 3.0 g exhibited a slight decrease in removal efficiency with 67% to 61% for COD removal. A better result in removing COD was also shown by GAC compared to the natural zeolite and CSMZ.
The percentage of turbidity removed by GAC in different dosages is described in Figure 4(c). The highest removal was indicated at adsorbent dosage 2.5 g with removal efficiency of 70% while the minimum removal was 52% recorded at the adsorbent dosage 0.01 g. However, starting from adsorbent dosage of 3.0 to 4.0 g, removal efficiency began to decrease to 68%, 67%, and 69% respectively.
The result of percentage removal of iron ion by GAC in peat water is presented in Figure 4(d). It was found that the rate of removal was rapid in the initial dosage between 0.01 g to 3.0 g at which the removal efficiency increased from 28% to 71% accordingly. Subsequently, a few significant changes in the rate of removal were observed. Possibly, at the beginning, the solute molecules were absorbed by the exterior surface of adsorbent particles, so the adsorption rate was rapid. However, after the optimum dose was reached, the adsorption of the exterior surface becomes saturated and thereby the molecules will need to diffuse through the pores of the adsorbent into the interior surface of the particle (Ahmad & Hameed, 2009).
3.4 Batch Column Experiment
On the first running, the column was packed with natural zeolite (1st layer), limestone (2nd layer), and GAC (3rd layer) as shown in Figure 5(a). Removal efficiency for colour, COD, turbidity, and iron ion was recognized to be increased when the contact time was increased. At the time interval 1 hour to 6 hours, however, the increment was not so significant. The removal efficiency at 1 hour treatment was 39%, 21%, 54%, 36% while at 6 hours treatment was 77%, 65%, 73%, 60% recorded for respective colour, COD, turbidity, and iron ion. Poor removal efficiency at 1 hour treatment indicated that the required time to remove all parameters were insufficient. It is evident that if the adsorption process is allowed to run for 24 hours on the column, the removal efficiency shows notable removal. Percentage removals of colour, COD, turbidity, and iron ion at 24 hours were 83%, 72%, 76%, 65% respectively. Furthermore, the highest removal for respective colour, COD, turbidity, and iron ion were obtained at 48 hours treatment with 87%, 81%, 86%, and 79% of removal efficiency.
Figure 5. Percentage removal of color, COD, turbidity, and Fe for 1st run(a), 2nd run(b), and 3rd run (c) at flowrate 30 ml/min
On the second running, the column was packed with CSMZ (1st layer), limestone (2nd layer), and GAC (3rd layer) as presented in Figure 5(b). The removal percentages of colour, COD, turbidity, and iron ion were noticed after 1 hour to be 52%, 49%, 71%, and 30% respectively. The time of contact between adsorbate and adsorbent is proven to play an important role during the uptake of pollutants from peat water samples by adsorption process. In addition, the development of charge on the adsorbent surface was governed by contact time and hence the efficiency and feasibility of an adsorbent for its use in water pollution control can also be predicted by the time taken to attain its equilibrium (Sharma, 2003). Removal efficiency of 90% for colour, 81% for COD, 91% for turbidity, and 57% for iron ion were obtained at 24 hours of contact time.
On the third running, the column was packed with a difference sequence of CSMZ (1st layer), GAC (2nd layer), and limestone (3rd layer) demonstrated in Figure 5(c). It can be seen that the adsorption of these four parameters were slightly rapid at time interval 1 hour to 6 hours treatment. Further gradual increment with the prolongation of contact time form 24 hours to 48 hours has also occurred. Observation at 1 hour treatment recorded the removal efficiency of 62%, 58%, 87%, and 48% for respective colour, COD, turbidity, and iron ion. Whereby, 6 hours treatment had yielded higher removal percentage removal of 75%, 77%, 93%, and 58% respectively for colour, COD, turbidity, and iron ion. Further removal of colour, COD, turbidity, and iron ion was recorded when the treatment was run for 24 hours which exhibited 92%, 91%, 98%, 77% of removal efficiency respectively. Prolonged time to 48 hours indeed showed better removal of colour, COD, turbidity, iron ion with percentage removal of 95%, 100%, 99%, and 89% respectively. It can be seen that the arrangement of CSMZ, GAC, and limestone has the highest removal efficiency for all parameters at the flow rate influent of 30 ml/min.
Figure 6. Percentage removal of color, COD, turbidity, and Fe against contact time for 2nd run(a) at flow rate 60 mL/min and at flowrate 90 mL/min (b)
The experimental adsorption behaviour was further seen for its adsorption capacity during 60 ml/min and 90 ml/min flow rate. In addition, the flow rate adjustment had also resulted in differences in surface loading rate in which the sample going through the surface area of adsorbent bed (horizontal surface area, A= 22.9 cm2) for 30 ml/min equals to 1.31 cm/min while the flow rate of 60ml/min equals to 2.62 cm/min, and the flow rate of 90 ml/min equals to 3.93 cm/min. The percentage removal for both flow rate adjustments of CSMZ, GAC, and limestone arrangement were exhibited in Figure 6 (a) and Figure 6 (b). Based on these Figures, lower removal efficiencies were indicated at 1 hour time interval of 6 hours of contact time. The percentage removals for both 60 ml/min and 90 ml/min flow rate at 1 hour were 57%, 56%, 80%, 38% and 49%, 58%, 61%, 35% for colour, COD, turbidity, and iron ion respectively. Subsequently, when the contact time was at 6 hours, the removal percentage were 70%, 79%, 88%, 56%, and 60%, 77%, 70%, 47%. However, the maximum removal efficiency at 48 hours for both flow rates was not much different from the 30ml/min flow rate.
3.5 Adsorption Isotherm
In the present investigation, the experimental data were tested with respect to both Freundlich and Langmuir isotherms. Based on the linearized Freundlich isotherm models for natural zeolite, CSMZ, GAC in terms of adsorptive capacity to remove colour, COD, turbidity, and iron ion, the majority of them exhibited fits for all adsorbate with regression value (R2) above 0.6, except for iron ion and turbidity for respective CSMZ, and GAC. On the other hand, the linearized Langmuir isotherm models for natural zeolite, CSMZ, GAC in terms of adsorptive capacity to remove colour, COD, turbidity, and iron ion, had exhibited fits for all adsorbate with regression value (R2) was at range of 0.242 to 0.912. The Langmuir isotherm model for all adsorption mechanisms were identified to have smaller R2 values compared to the Freundlich isotherm model. Thereby, it can be concluded that the Freundlich isotherm model was more applicable in determining the adsorption mechanisms for this study.
3.6 Peat Water Quality Post Column Treatment
Peat water treatment in column with serial sequence of natural zeolite, CSMZ, and limestone had exhibited the highest removal with percentage removal at 48 hours at 95%, 100%, 99%, and 89% for colour, COD, turbidity, and iron ion respectively. Final readings at 48 hours treatment on pH, TDS, DO, conductivity, salinity, colour, turbidity, COD, and iron ion were 7.78, 74 mg/l, 4.03 mg/l, 137 uS/cm, 0.05 ppt, 12 TCU, 0.23 NTU, 0 mg/l, and 0.11 mg/l respectively (see Table 3). These findings, on the other hand, have indicated that peat water treatment had successfully produced water which satisfied the standard drinking water quality.
Table 3. The characteristics of results of peat water treatment from Beriah Peat Swamp Forest
Note: 1. *)Malaysian standard for drinking water quality;2. NA = Not analyzed.
From the results presented in this paper, the following conclusions can be drawn:
1) The optimum removal of colour, COD, and turbidity for all adsorbents were observed to occur during acidic conditions at pH range 2 – 4 whereas for iron ion, the maximum removal was noted at pH range 6 – 8.
2) At pH 2, CSMZ yielded the highest removal for colour and turbidity with removal efficiency of 90% and 98% respectively. Meanwhile, GAC has the highest percentage removal of COD at pH 4 with removal efficiency obtained about 61% while at pH 6, GAC exhibited the best removal of iron ion with percentage removal around 80%.
3) CSMZ revealed stronger adsorptive capacity for colour, COD, and turbidity compared to natural zeolite.
4) The optimal removal was achieved for the serial sequence of CSMZ (1st layer), GAC (2nd layer), and Limestone (3rd layer) with the adsorbent media at 30 ml/min of flow rate.
5) Freundlich isotherm was more reliable to describe the adsorption mechanisms of colour, COD, turbidity, and iron ion for natural zeolite, CSMZ, and GAC.
The authors wish to acknowledge the financial support from the School of Civil Engineering, Engineering Campus, Universiti Sains Malaysia and Universiti Sains Malaysia (Short Term Grant No. 304/PAWAM/60312015).
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Modern Applied Science; Vol. 7, No. 2; 2013
ISSN 1913-1844 E-ISSN 1913-1852
Published by Canadian Center of Science and Education
S. Syafalni1, Ismail Abustan1, Aderiza Brahmana1, Siti Nor Farhana Zakaria1 & Rohana Abdullah1
1 School of Civil Engineering, Engineering Campus, Universiti Sains Malaysia, Nibong Tebal, Penang, Malaysia. Correspondence: S. Syafalni, School of Civil Engineering, Engineering Campus, Universiti Sains Malaysia,
Nibong Tebal 14300, Penang, Malaysia. E-mail: email@example.com
Received: December 3, 2012 Accepted: January 14, 2013 Online Published: January 22, 2013 doi:10.5539/mas.v7n2p39 URL: http://dx.doi.org/10.5539/mas.v7n2p39
Shared via Creative Commons Attribution 3.0 Unported license