Science and Industry Updates
TweetAll Myron L meters are factory calibrated with NIST traceable Standard Solutions having specific conductivity/ppm values. MyronL Standard Solutions are made under strictly controlled conditions using reagent grade salts. These salts are mixed with deionized water having a resistivity of at least 5 megohms-cm purity. Myron L Standard Solutions have an accuracy of +1% based […]
All Myron L meters are factory calibrated with NIST traceable Standard Solutions having specific conductivity/ppm values. MyronL Standard Solutions are made under strictly controlled conditions using reagent grade salts. These salts are mixed with deionized water having a resistivity of at least 5 megohms-cm purity.
Myron L Standard Solutions have an accuracy of +1% based on values published in the International Critical Tables and traceable to the National Institute of Standards and Technology. NIST certificates , while not available on Ultrapens, are available on most other Myron L meters and solutions. Check the product page for the NIST certificate option. See example below:
Regular use of these solutions is recommended to ensure specified instrument accuracy. Frequency of conductivity recalibration depends upon use, but once every month should be sufficient for an instrument used daily. pH models, depending upon use, should be recalibrated with pH 7 Buffer every 1-2 weeks, and checked with pH 4 and/or 10 Buffers at similar intervals. pH Sensor Storage Solution is recommended for keeping the pH sensor hydrated. Myron L solutions are available in quart/1 ltr., gallon/3,8 ltr. and 2 oz./59 ml plastic bottles, ready to use.
Below is the official NIST traceability policy from the website of the National Institute of Standards and Technology.
The mission of NIST is to promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology in ways that enhance economic security and improve our quality of life. To help meet the measurement and standards needs of U.S. industry and the nation, NIST provides calibrations, standard reference materials, standard reference data, test methods, proficiency evaluation materials1, measurement quality assurance programs, and laboratory accreditation services that assist a customer in establishing traceability of measurement results.
Metrological traceability requires the establishment of an unbroken chain of calibrations to specified references. NIST assures the traceability of measurement results that NIST itself provides, either directly or through an official NIST program or collaboration. Other organizations are responsible for establishing the traceability of their own results to those of NIST or other specified references. NIST has adopted this policy statement to document the NIST role with respect to traceability.
Statement of Policy
To support the conduct of its mission and to ensure that the use of its name, products, and services is consistent with its authority and responsibility, NIST adopts for its own use and recommends for use by others the definition of metrological traceability2 provided in the most recent version of the International Vocabulary of Metrology: “property of a measurement result whereby the result can be related to a reference through a documented unbroken chain of calibrations, each contributing to the measurement uncertainty.” (International Vocabulary of Metrology – Basic and General concepts and Associated Terms (VIM), definition 2.41, see Reference ).
To support the conduct of its mission and to ensure that the use of its name, products, and services is consistent with its authority and responsibility, NIST:
1. Adopts for its own use and recommends for use by others the definition of traceability provided in the most recent version of the International vocabulary of metrology – Basic and general concepts and associated terms (VIM): “property of a measurement result whereby the result can be related to a reference through a documented unbroken chain of calibrations, each contributing to the measurement uncertainty..” .
2. Establishes metrological traceability of the results of its own measurements and of results provided to customers in NISTcalibration and measurement certificates, operating in accordance with the NIST Quality System for Measurement Services.
3. Asserts that providing support for a claim of metrological traceability of the result of a measurement is the responsibility of theprovider of that result, whether that provider is NIST or another organization; and that assessing the validity of such a claim is the responsibility of the user of that result.
4. Communicates, especially where claims expressing or implying the contrary are made, that NIST does not define, specify,assure, or certify metrological traceability of the results of measurements except those that NIST itself provides, either directly or through an official NIST program or collaboration. (See also NIST Administrative Manual, Subchapter 5.03, NIST Policy on Use of its Name in Advertising.)
5. Collaborates on development of standard definitions, interpretations, and recommended practices with organizations that have authority and responsibility for variously defining, specifying, assuring, or certifying metrological traceability.
6. Develops and disseminates technical information on traceability and conducts coordinated outreach programs on issues of traceability and related requirements.
7. Assigns responsibility for oversight of implementation of the NIST policy on metrological traceability to the NIST Measurement Services Advisory Group (MSAG).
1 Underlined terms are defined in III Glossary of Terms in the Supplementary Materials section following.
2 The full term, “metrological traceability” is preferred when there is a risk of confusion with other meanings of the abbreviated term “traceability”, which is sometimes used to refer to the “history” or “trace” of an item. The abbreviated term is also used in this document to improve readability, since it is clear that “metrological traceability” is meant in every case.
The National Institute of Standards and Technology (NIST) is an agency of the U.S. Department of Commerce. Original found here: http://www.nist.gov/traceability/nist_traceability_policy_external.cfm
TweetWHAT IS ORP? Oxidation Reduction Potential or Redox is the activity or strength of oxidizers and reducers in relation to their concentration. Oxidizers accept electrons, reducers lose electrons. Examples of oxidizers are: chlorine, hydrogen peroxide, bromine, ozone, and chlorine dioxide. Examples of reducers are sodium sulfite, sodium bisulfate and hydrogen sulfide. Like acidity and alkalinity, […]
WHAT IS ORP?
Oxidation Reduction Potential or Redox is the activity or strength of oxidizers and reducers in relation to their concentration. Oxidizers accept electrons, reducers lose electrons. Examples of oxidizers are: chlorine, hydrogen peroxide, bromine, ozone, and chlorine dioxide. Examples of reducers are sodium sulfite, sodium bisulfate and hydrogen sulfide. Like acidity and alkalinity, the increase of one is at the expense of the other.
A single voltage is called the Oxidation-Reduction Potential, where a positive voltage shows a solution attracting electrons (oxidizing agent). For instance, chlorinated water will show a positive ORP value whereas sodium sulfite (a reducing agent) loses electrons and will show a negative ORP value.
ORP is measured in millivolts (mV), with no correction for solution temperature. Like pH, it is not a measurement of concentration directly, but of activity level. In a solution of only one active component, ORP indicates concentration. As with pH, a very dilute solution will take time to accumulate a measurable charge.
An ORP sensor uses a small platinum surface to accumulate charge without reacting chemically. That charge is measured relative to the solution, so the solution “ground” voltage comes from the reference junction – the same type used by a pH sensor.
HISTORY OF ORP
ORP electrodes were first studied at Harvard University in 1936. These studies showed a strong correlation of ORP and bacterial activity. These tests were confirmed by studies on drinking water and swimming pools in other areas of the world. In 1971 ORP (700 mV) was adopted by the World Health Organization (WHO) as a standard for drinking water. In 1982 the German Standards Agency adopted the ORP (750 mV) for public pools and in 1988 the National Swimming Pool Institute adopted ORP (650 mV) for public spas.
WHERE IS ORP USED?
As you can tell by the previous paragraphs, ORP is used for drinking water, swimming pools and spas. However, ORP is also used for cooling tower disinfection, groundwater remediation, bleaching, cyanide destruction, chrome reductions, metal etching, fruit and vegetable disinfection and dechlorination.
In test after test on poliovirus, E. coli, and other organisms, a direct correlation between ORP and the rate of inactivation was determined. It is, therefore, possible to select an individual ORP value, expressed in millivolts, at which a predictable level of disinfection will be achieved and sustained regardless of variations in either oxidant demand or oxidant concentration. Thus, individual ORP targets, expressed in millivolts, can be determined for each application, which will result in completely reliable disinfection of pathogens, oxidation of organics, etc. Any level of oxidation for any purpose can be related to a single ORP number which, if maintained, will provide utterly consistent results at the lowest possible dosage.
WHY USE ORP?
ORP is a convenient measure of the oxidizer’s or reducer’s ability to perform a chemical task. ORP is not only valid over a wide pH range, but it is also a rugged electrochemical test, which can easily be accomplished using in-line and handheld instrumentation. It is by far a more consistent and reliable measurement than say chlorine alone.
LIMITATIONS FOR ORP
As with all testing, ORP has certain limitations. The speed of response is directly related to the exchange current density which is derived from concentration, the oxidation reduction system, and the electrode. If the ORP of a sample is similar to the ORP of the electrode, the speed will be diminished.
Carryover is also a possible problem when checking strong oxidizers or reducers, and rinsing well will help greatly.
Although a better indicator of bactericidal activity, ORP cannot be used as a direct indicator of the residual of an oxidizer due to the effect of pH and temperature on the reading. ORP can be correlated to a system by checking the oxidizer or reducer in a steady state system with a wet test, and measuring pH. If the system stays within the confines of this steady state parameter (usually maintained by in- line or continuous control), a good correlation can be made. The best recommendation for ORP is to use wet tests, and over three test periods correlate the ORP values to those test parameters.
FREE CHLORINE CONVERSION USING ORP
The most ubiquitous and cost-effective sanitizing agent used in disinfection systems is chlorine. When chlorine is used as the sanitizer, free chlorine measurements are required to ensure residual levels high enough for ongoing bactericidal activity. Myron L meters accurately convert ORP measurements to free chlorine based on the understanding of the concentrations of the forms of free chlorine at a given pH and temperature. The conversion is accurate when chlorine is the only oxidizing/reducing agent in solution and pH is stable between 5 and 9. This pH range fits most applications because pH is usually maintained such that the most effective form of free chlorine, hypochlorous acid, exists in the greatest concentration with respect to other variables such as human tolerance.
MYRON L METERS
Myron L offers a variety of handheld instruments and in-line Monitor/controllers that may be used to measure, monitor and/or control ORP. The latest is the Ultrapen PT3, ORP/Redox and Temperature Pen. The Ultrameter III™ 9PTKA, Ultrameter II™ 6PFCE, PoolPro™ PS6FCE and PS9TK, and D-6 Digital Dialysate Meter™ are multi-parameter handheld instruments with ORP and FCE free chlorine measuring capabilities. These instruments also have the capability to measure conductivity, TDS, resistivity, pH, mineral/salt concentration and temperature, making them the preferred instruments for all water treatment professionals. The 720 Series II Monitor/controllers are an excellent choice for continuous in-line measurements.
For additional information, visit us at MyronLMeters.com.
Tweet In water remote sensing, or ‘ocean color‘, people extract water quality parameters from satellite imagery. Probably the most interesting parameter is chlorophyll-a concentration, which can be related to the phytoplankton (algae, cyanobacteria) biomass in the water. Applications are quite diverse, ranging from harmful algal […]
In water remote sensing, or ‘ocean color‘, people extract water quality parameters from satellite imagery. Probably the most interesting parameter is chlorophyll-a concentration, which can be related to the phytoplankton (algae, cyanobacteria) biomass in the water. Applications are quite diverse, ranging from harmful algal blooms early warning systems, eutrophication assessment to climate change research – to name a few.
The same algorithms are used on spectra taken directly in the field to calibrate/validate remotely sensed concentrations. However, spectrometers used for these field measurements are quite expensive (>20k USD) and often not trivial to operate. This hampers the use of ‘water color’ by a wider audience, e.g. water managers, fisheries and especially the public that might want to know what the water quality in their pond is.
Spectra from cheap, open source spectrometers can potentially bridge this gap.
From my experience with the foldable spectrometer and the desktop kit I see three main issues: sensitivity, spectral resolution and calibration.
- Sensitivity Water appears often very dark, especially if only little scattering substance is present. In contrast, the reflection of the direct sun light on the water surface is extremely bright. Thus, to resolve the ‘true’ water color, the instrument has to be relatively sensitive.
- Spectral Calibration and Calibration Pigment absorption, other optically active substances and the water itself cause the water’s color. Pigments in phytoplankton, such as the main photosynthetic pigment chlorophyll-a, have very sharp absorption features. In order to resolve those peaks, the spectral resolution has has to be sufficiently high and the calibration sufficiently accurate.
These days I had the opportunity to take the desktop kit out on a fieldwork campaign on Lake Peipsi and Lake Vortsjarv in Estonia. Fortunately, this little Baltic country has one of the best 3G-networks worldwide and so I could use the spectral workbench to upload my spectra straight from the boats – pretty cool! However, an offline version of the workbench is essential (couldn’t get the local webserver running so far). The spectra are available here: Lake Peipsi (R_sky, R_water), Lake Vortsjarv (R_sky, R_water).
- Preparations / Calibration The initial wavelength calibration with fluorescent light line peaks is pretty brilliant. Still, at least a rudimentary intensity calibration is necessary to interpret the shape of the spectra. I can use our calibration lab for this purpose and give some feedback to the community on how the spectral response curve of at least my desktop kit’s webcam looks like. For public use, I’m thinking of using daylight spectra as a reference, as the shape is rather stable (not the intensity, due to atmospheric conditions). Maybe we can find a better solution for that.
- Measurements We need at least two measurements in order to run a spectral unmixing algorithm: upwelling radiance (light from the water) and downwelling irradiance (complete skylight). As we most likely won’t be able to build a cheap spectrometer that has even vaguely defined entry optics (e.g. 9deg field of view for the radiance and a perfect cosine response for the irradiance), some improvisation is needed. For the irradiance measurement I’m thinking of using a white table-tennis ball on top of the slit as a diffusor. The radiance measurement is mainly hampered by water surface reflections. To avoid those, I’d like to measure either just underneath the water surface (–> how to make the spectrometer water tight) or to use a sun shade (such as for camera lenses). For now, a black bucket with a hole in the bottom should do the job.
- Postprocessing The current procedure to extract a spectrum from the webcam-video is pretty smart and straightforward but probably not optimal if sensitivity is a priority. Currently, as I understand, only one row of the ‘stitched spectral image’ is used to extract the spectrum (‘set sample row’ in the workbench). Skylight, as well as the water leaving radiance are stable on the timescales of a measurement. Therefore I’d suggest to average over all rows to improve the signal to noise ratio. If that is not enough, one could think about extracting not only one line from the webcam’s video stream but e.g. ten and save the average in the stitched spectral image. In a last desperate step, one could use the whole webcam image and correct for the curvature caused by the DVD, however, I don’t think this will be necessary.
- This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.
Research by philippg
TweetIntroduction Oceans contain over 97.2% of the planet’s water. Because of the high salinity of ocean water and the significant costs associated with seawater desalination most of the global water supply has traditionally come from fresh water sources – groundwater aquifers, rivers and lakes. Today, however, changing climate patterns combined with population growth pressures and […]
Oceans contain over 97.2% of the planet’s water. Because of the high salinity of ocean water and the significant costs associated with seawater desalination most of the global water supply has traditionally come from fresh water sources – groundwater aquifers, rivers and lakes. Today, however, changing climate patterns combined with population growth pressures and limited availability of new and inexpensive fresh water supplies are shifting the water industry’s attention: in an emerging trend, the world is reaching to the ocean for fresh water.
Until recently, desalination was limited to desert-climate dominated regions. Technological advances and an associated decrease in water production costs over the past decade have expanded its use in coastal areas traditionally supplied with fresh water resources. Today, desalination plants provide approximately 1% of the world’s drinking water supply and the commissioned and installed desalination capacity has been increasing exponentially over the past 10 years.
Higher Productivity Membrane Elements
A key factor that has contributed to the dramatic decrease of seawater desalination costs over the past 10 years is the advancement of the SWRO membrane technology. Today’s high-productivity membrane elements are designed with several features that yield more fresh water per membrane element than any time in the recent history of this technology: higher surface area, enhanced permeability and denser membrane packing. Increasing active membrane leaf surface area and permeability allows it to gain significant productivity using the same size (diameter) membrane element. Active surface area of the membrane elements is typically increased by membrane production process automation, by denser membrane leaf packing and by adding membrane leaves within the same element.
The total active surface area in a membrane element is also be increased by increasing membrane size/diameter. Although 8-inch SWRO membrane elements are still the “standard” size most widely used in full-scale applications, larger 16-inch and 18-inch size SWRO membrane elements have become commercially available over the past three years and have already found full-scale implementation in several SWRO projects worldwide (Bergman & Lozier, 2010).
In the second half of the 1990s, the typical 8-inch SWRO membrane element had a standard productivity of 5,000 to 6,000 gallons per day (gpd) at salt rejection of 99.6%. In 2003, several membrane manufacturers introduced high-productivity seawater membrane elements that are capable of producing 7,500 gpd at salt rejection of 99.75%. Just one year later, even higher productivity (9,000 gpd at 99.7% rejection) seawater membrane elements were released on the market. Over the past three years SWRO membrane elements combining productivity of 10,000 to 12,000 gpd and high-salinity rejection have become commercially available and are now gaining wider project implementation.
The newest membrane elements provide flexibility and choice and allow users to trade productivity and pressure/power costs. The same water product quality goals can be achieved in one of two general approaches: (1) reducing the system footprint/construction costs by designing the system at higher productivity, or (2) reducing the system’s overall power demand by using more membrane elements, designing the system at lower flux and recovery, and taking advantage of newest energy recovery technologies which further minimize energy use if the system is operated at lower (35% to 45%) recoveries.
Innovative hybrid membrane configuration combining SWRO elements of different productivity and rejection within the same vessel which are sequenced to optimize the use of energy introduced with the feed water to the desalination vessels is also finding wider implementation. In addition, a number of novel membrane SWRO train configurations have been developed over the past five years aiming to gain optimum energy use and to reduce capital costs for production of high-quality desalinated water.
Design and Equipment Enhancements for Lower Energy Use
Energy is one of the largest expenditures associated with seawater desalination. Figure 1 shows a distribution of the energy use within a typical seawater desalination plant. As shown on this figure, the SWRO system typically uses over 70% of the total plant energy.
Figure 1 – Energy Use Breakdown of Typical SWRO Desalination Plant
Increased High Pressure Pump Efficiency
One approach for reducing total RO system energy use which is widely applied throughout the desalination industry today is to incorporate larger, higher efficiency centrifugal pumps which serve multiple RO trains. This trend stems from the fact that the efficiency of multistage centrifugal pumps increases with their size (pumping capacity). For example, under a typical configuration where individual pump is dedicated to each desalination plant RO train, high pressure pump efficiency is usually in a range of 80% to 83%. However, if the RO system configuration is such that a single high pressure pump is designed to service two RO trains of the same size, the efficiency of the high pressure pumps could be increased to up to 85%.
Proven design that takes this principle to the practical limit of centrifugal pump efficiency (≈ 90%) is implemented at the 86 MGD Ashkelon seawater desalination plant in Israel, where two duty horizontally split high pressure pumps are designed to deliver feed seawater to 16 SWRO trains at guaranteed long term efficiency of 88%. Continuous plant operational track record over the past 5 years shows that the actual efficiency level of these pumps under this configuration is close to 90%.
A current trend for smaller desalination facilities (plants with fresh water production capacity of 250,000 gpd or less) is touse positive displacement (multiple-piston)high-pressure pumps and energy recovery devices, which often are combined into a single unit. These systems are configured to take advantage of the high efficiency of the positive displacement technology which practically can reach 94% to 97%.
Improved Energy Recovery
Advances in the technology and equipment allowing the recovery and reuse of the energy applied for seawater desalination have resulted in a reduction of 80% of the energy used for water production over the last 20 years. Today, the energy needed to produce fresh water from seawater for one household per year (~2,000 kW/yr) is less than that used by the same household’s refrigerator.
While five years ago, the majority of the existing seawater desalination plants used Pelton Wheel-based technology to recover energy from the SWRO concentrate, today the pressure exchanger-based energy recovery systems dominate in most desalination facility designs. The key feature of this technology is that the energy of the SWRO system concentrate is directly applied to pistons that pump intake seawater into the system. Pressure-exchanger technology typically yields 5% to 15% higher energy recovery savings than the Pelton-Wheel-based systems.
Figure 2 depicts the configuration of a typical pressure exchanger-based energy recovery system. After membrane separation, most of the energy applied for desalination is contained in the concentrated stream (brine) that also contains the salts removed from the seawater. This energy-bearing stream (shown with red arrows on Figure 2) is applied to the back side of pistons of cylindrical isobaric chambers, also known as pressure exchangers (shown as yellow cylinders on Figure 2). These pistons pump approximately 45% to 50% of the total volume of seawater fed into the RO membranes for salt separation. Since a small amount of energy (4 to 6%) is lost during the energy transfer from the concentrate to the feed water, this energy is added back to feed flow by small booster pumps to cover for the energy loss. The remainder (45% to 50%) of the feed flow is handled by high-pressure centrifugal pumps. Harnessing, transferring and reusing the energy applied for salt separation at very high efficiency (94% to 96%) by the pressure exchangers allows a dramatic reduction of the overall amount of electric power used for seawater desalination.In most applications, a separate energy recovery system is dedicated to each individual SWRO train. However, some recent designs include configurations where two or more RO trains are serviced by a single energy recovery unit.
Figure 2 – Pressure Exchanger Energy Recovery System
While the quest to lower energy use continues, there are physical limitations to how low the energy demand could go using RO desalination. The main limiting factors are the osmotic pressure that would need to be overcome to separate the salts from the seawater and the amount of water that could be recovered from a cubic meter of seawater before the membrane separation process is hindered by salt scaling on the membrane surface and the service systems. This theoretical limit for the entire seawater desalination plant is approximately 4.5 kWh/kgal.
Seawater Desalination Cost Trends
Advances in seawater RO desalination technology during the past two decades, combined with transition to construction of large capacity plants, and enhanced competition by using the Build-Own-Operate-Transfer (BOOT) method of project delivery have resulted in an overall downward cost trend. While the costs of production of desalinated water have benefited from the most recent advances in desalination technology, the cost spread among individual desalination projects observed over the past three years is fairly significant.
Most recently commissioned large seawater desalination projects worldwide produce desalinated water at an all-inclusive cost of US$3.0 to US$5.5/kgal. However, the traditionally active desalination markets in Israel and Northern Africa (i.e., Algeria) have yielded desalination projects with exceptionally low water production costs (110 MGD SWRO Plant in Sorek, Israel – US$2.00/kgal; 87 MGD Hadera Desalination Plant, Israel – US$2.27/kgal; 132 MGD Magtaa SWRO Plant in Algeria – US$2.12/kgal).
On the other end of the cost spectrum, some of the most recent seawater desalination projects in Australia had been associated with the highest desalination costs observed over the past 10 years – i.e., the Gold Coast SWRO Plant in Queensland at US$10.95/kgal; the Sydney Water Desalination Plant at US$8.67/kgal; and the Melbourne’s Victorian Desalination Plant at US$9.54/kgal.
While this extreme cost disparity has a number of site-specific reasons, the key differences associated with the lowest and highest-cost projects are related to five main factors: (1) desalination site location; (2) environmental considerations; (3) phasing strategy; (4) labor market pressures; (5) method of project delivery and risk allocation between owner and private contractor responsible for project implementation.
The desalination projects with highest and lowest costs have a very distinctive difference in terms of project phasing strategy. While the large high-cost projects incorporate single intake and discharge tunnel structures built for the ultimate desalination plant capacity (which often equals two times the capacity of the first project phase), the desalination projects on the low end of the cost spectrum use multi-pipe intake systems constructed mainly from high density polyethylene (HDPE) that have capacity commensurate with the production capacity of the desalination plant. Additional multiple intake pipes and structures are installed as needed at the time of plant expansion for these facilities.
While the single-phase construction of desalination plant intake and outfall structures dramatically reduces the environmental and public controversy associated with the plant capacity expansion at a later date, this “ease-of-implementation” benefit typically comes with an overall cost penalty. The notion that the larger costs associated with building complex intake and outfall concrete tunnels in one phase will somehow be offset by economies of scale usually does not yield the expected overall project cost savings. The main reason is the fact that the cost of 100 linear feet of deep concrete intake or discharge tunnel is over four times higher than the cost of the same capacity intake or discharge constructed from multiple HDPE pipes located on the ocean bottom, while the economy of scale from one-stage construction is usually less than 30%.
Labor market differences can have a profound impact on the cost of construction of desalination projects. The overlapping schedules of the series of large desalination projects in Australia have created temporary shortage of skilled labor, which in turn has resulted in a significant increase in unit labor costs. Since labor expenditures are usually 30% to 50% of the total desalination plant construction costs, a unit labor rate increase of 20% to as high as up to 100%, could trigger sometimes unexpected and not frequently observed project cost increases.
Without exception, the lowest cost desalination projects to date have been delivered under turnkey BOOT contracts where private sector developers share risks with the public sector based to their ability to control and mitigate the respective project related risks.
On the other hand, the most costly desalination projects worldwide have been completed under an “alliance”[(a type of design-build-operate (DBO)] model where the public utility retains the ownership over the project assets but expects the DBO team to take practically all project-related risks. In this case, DBO contractors take upon project risks over which they have limited or no control, by delivering very conservative designs, incorporating high contingency margins in the price of their construction, operation and maintenance services, and by insuring these project risks at very high premiums. As a result, the projects delivered under such structure carry very high contingencies and upfront insurance and performance security payments which ultimately reflect on the overall increase of the cost of water production.
While under a typical BOOT project, the insurance and contingency costs are usually well below 20% of the total capital costs, projects with disproportionate transfer of risk to the private contractor result in built-in insurance and contingency premiums which exceed well over 30% of the total project capital costs. As a result, most often benefits gained from using state-of-the-art technologies, equipment and design, are negated by overly burdensome insurance and contingency expenditures and high cost of project funding.
Seawater Desalination Challenges in US
Water Production Costs
Currently, the cost of desalinating seawater in the US is relatively high compared to that of traditional low-cost water sources (groundwater and river water) and to production costs for water reclamation and reuse for irrigation and industrial use. Indeed, the cost of traditional local groundwater water supplies in some parts of the US are as low as US$0.50/kgal to US$0.90/kgal. However, the quantity of such low-cost sources in coastal urban centers of California, Texas, Florida, South Carolina and other parts of the US exposed to recent long-term drought pressures is very limited.
The generally lower costs for production of reclaimed water and for implementation of water conservation measures have often been used as an argument against the wider use of seawater desalination. This argument however, is fatally flawed by the fact that water conservation and reuse do not create new sources of drinking water – they are merely a rational tool to maximize the beneficial use of the available water supply resources. Under conditions of prolonged drought when the available water resources cannot be replenished at the rate of their use, aggressive reuse and conservation can help but may not completely alleviate the need for new water resources and water rationing.
Typically, seawater desalination cost benefits extend beyond the production of new water supplies. If seawater desalination is replacing the use of over-pumped coastal or inland groundwater aquifers, or is eliminating further stress on environmentally sensitive estuary and river habitats, than the higher costs of this water supply alternative would also be offset by its environmental benefits. Similarly, seawater desalination provides additional benefits in the time of drought where traditional water supplies may not be reliable and their scarcity may increase their otherwise relatively low costs.
Salt separation from seawater requires a significant amount of energy to overcome the naturally occurring osmotic pressure exerted on the reverse osmosis membranes. This in turns makes seawater desalination several times more energy intensive than conventional treatment of fresh water resources. Table 1 presents the energy use associated with various water supply alternatives. The table does not incorporate the costs associated with raw water treatment and product water delivery.
Table 1 – Energy Use of Various Water Supply Alternatives
While energy use for seawater desalination is projected to decrease by 10 to 20 % in the next 5 years as a result of technological advances discussed previously, the total energy demand for conventional water treatment would likely increase by 15 to 20 % in the same time frame because of the energy demand associated with the additional treatment (such as micro- or ultra-filtration, ozonation, UV disinfection, etc.) which would be needed in order to meet the most recent regulatory requirements for production of safe drinking water in the USA.
A number of the seawater desalination projects under consideration in California and Florida are proposed to be collocated with power generation plants which currently use seawater for production of electricity. Under the collocation configuration the desalination plant does not have a separate intake and discharge to the ocean and both the desalination plant intake and desalination plant discharge are connected to the exiting power plant discharge outfall or canal.
Collocation yields a number of benefits mainly because it avoids construction and permits for new intake and concentrate discharge facilities, and because of the energy cost savings associated with the desalination of warmer source water. However this intake configuration alternative has been considered undesirable by some environmental groups due to the potential loss of marine organisms caused by the impingement of marine organisms against the screens of the power plant intake and their entrainment inside the power plant conveyance and cooling system and subsequently inside the desalination plant.
Based on recently introduced regulatory requirements, the 21 once-through cooling plants along the California coast are required to prepare comprehensive plans for discontinuation of their use of open intakes and switching to air-cooling towers or to water close-circulation cooling towers in order to reduce impingement and entrainment of marine organisms.
Opponents of collocated seawater desalination plants have often present the argument that if the power plant changes its cooling system in the future, seawater desalination under collocated configuration at the particular location would no longer be available. This argument however, is unfounded in reality, because even if the host power plants abandon once-through cooling in the future, the desalination projects will still retain the main cost-benefits of collocation – avoidance of the need to construct a new intake and outfall. The cost savings from the use of the existing power plant intake and outfall facilities would be over 25%, resulting in a significant net benefit with or without the power plant in operation.
Recent studies of wedge-wire screens in Santa Cruz, California indicate that this type of open intake may prove to be a viable alternative for dramatic reduction in impingement and entrainment of marine organisms. Typically, wedge-wire screens are designed to be placed in a water body where significant prevailing ambient cross flow current velocities (³ 1 ft/s) exist. This cross high flow velocity allows organisms that would otherwise be impinged on the wedge-wire intake to be carried away with the flow.
A 2-mm cylindrical wedge wire screen intake is also planned to be tested for one year at the West Basin Municipal Water District’s Ocean Water Desalination Demonstration Facility in Redondo Beach. This demonstration facility is currently under operation.
Various sub-surface intake technologies (i.e., beach wells, horizontally directionally drilled and slant wells and innovative infiltration gallery configurations) have been heavily promoted by the California Coastal Commission and local environmental groups as a viable alternative to power plant collocation and construction of new open intakes along the California coast. Ongoing long-term studies of subsurface intakes in Long Beach and Dana Point, California are expected to provide comprehensive data that would allow completing a scientifically-based analysis of the viability and performance benefits of alternative subsurface intakes.
Seawater desalination plants along the US coastline would produce concentrate of salinity that is approximately 1.5 to 2 times higher than the salinity of the ambient seawater (i.e., in a range of 52 ppm to 67 ppm). While most marine organisms can adapt to this increase in salinity, some aquatic species such as abalone, sea urchins, sand dollars, sea bass and top smelt, are less tolerant to high salinity concentrations. Therefore, thorough assessment of the environmental impact of the discharge of concentrate and of any other byproducts of the seawater treatment process is a critical part of the evaluation of project viability.
At seawater desalination projects that are proposed to be collocated with power plants, the desalination plant discharge is planned to be diluted with the cooling water of the power plant to salinity levels that typically do not have significant impact on aquatic life. The magnitude and significance of impact, however, mainly depend on the type of marine organisms inhabiting the area of the discharge and on the hydrodynamic conditions of the ocean in this area, such as currents, tide, wind and wave action, which determine the time of exposure of the marine organisms to various salinity conditions.
Extensive salinity tolerance studies completed over the past several years at the Carlsbad seawater desalination demonstration facility in California indicate that after concentrate dilution with power plant cooling seawater down to 40 ppm or less, the combined discharge does not exhibit chronic toxicity on sensitive test marine species. Recent acute toxicity studies at this facility further show that sensitive marine species can event tolerate salinity of 50 ppm or more over a short period of time (2 days or less).
Some seawater desalination projects are planning to use deep injection wells to discharge the high-salinity seawater concentrate generated during the reverse osmosis separation process. However, the full-scale experience with this concentrate disposal method to date is very limited.
A third disposal alternative, besides injection wells and co-disposal with power plant cooling water, currently under consideration for implementation at a number of seawater desalination projects in the US, is the discharge of the concentrate through existing wastewater treatment plant ocean outfall. International experience with such co-located discharges is fairly limited. However, this technology may have a number of merits similar to these derived from the collocation of desalination and power generation plants.
Proving that concentrate discharge from a seawater desalination plant is environmentally safe requires thorough engineering analysis including: hydrodynamic modeling of the discharge; whole effluent toxicity testing; salinity tolerance analysis of the marine species endogenous to the area of discharge; and reliable intake water quality characterization that provides basis for assessment of concentrate’s make up and compliance with the numeric effluent quality standards applicable to the point of discharge. Comprehensive pilot testing of the proposed seawater desalination system is very beneficial for the project environmental impact analysis.
Summary and Conclusions
Over the past decade seawater desalination has experienced an accelerated growth driven by advances in membrane technology and environmental science. While conventional technologies, such as sedimentation and filtration have seen modest advancement since their initial use for potable water treatment several centuries ago, new more efficient seawater desalination membranes and membrane technologies, and equipment improvements are released every several years. Although, no major technology breakthroughs are expected to bring the cost of seawater desalination further down dramatically in the next several years, the steady trend of reduction of desalinated water production costs coupled with increasing costs of water treatment driven by more stringent regulatory requirements, are expected to accelerate the current trend of increased reliance on the ocean as an attractive and competitive water source. This trend is forecasted to continue in the future and to further establish ocean water desalination as a reliable drought-proof alternative for many coastal communities in the United States and worldwide.
Although seawater desalination projects in the US face a number of environmental challenges, these challenges can be successfully addressed by carefully selecting the project site, by implementing state-of-the art intake and concentrate discharge technologies and by incorporating energy efficient and environmentally sound equipment and systems.
Nikolay Voutchkov, PE, BCEE Water Globe Consulting, LLC, Stamford, CT. Editor of Desalination Technology: Health and Environmental Impacts (2010) IWA Publishing.
Water Desalination and European Research
Nanofiltration for Brackish Desalination
GWI – Global Water Intelligence: Market-leading Analysis of the International Water Industry, 10, pp.9, 2009.
Bergman R.A. and J.C. Lozier.“Large-Diameter Membrane Elements and Their Increasing Global Use”. IDA Journal. pp. 16, First Quarter 2010.
Global Water Intelligence
International Desalination Ascociation
Joseph Cotruvo, Nikolay Voutchkov, John Fawell, Pierre Payment, David Cunliffe, Sabine Lattemann Desalination Technology: Health and Environmental Impacts (2010) IWA Publishing.
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TweetJohn Roach, Contributing Writer, NBC News Elevated levels of methane and other stray gases have been found in drinking water near natural gas wells in Pennsylvania’s gas-rich Marcellus shale region, according to new research. In the case of methane, concentrations were six times higher in some drinking water found within one kilometer of drilling operations. […]
John Roach, Contributing Writer, NBC News
Elevated levels of methane and other stray gases have been found in drinking water near natural gas wells in Pennsylvania’s gas-rich Marcellus shale region, according to new research. In the case of methane, concentrations were six times higher in some drinking water found within one kilometer of drilling operations.
TweetMyron L Meters provides introductory as well as professional level material on water quality and water treatment. Did you know that Myron L Meters carries a meter specifically for testing RO systems (see below)? Water purification systems have purified brackish water and sea water for the military, businesses and farms in many different locations on […]
Myron L Meters provides introductory as well as professional level material on water quality and water treatment. Did you know that Myron L Meters carries a meter specifically for testing RO systems (see below)?
Water purification systems have purified brackish water and sea water for the military, businesses and farms in many different locations on planet Earth. Reverse osmosis water purification will create clean drinkable water when used on your drinking water.
Reverse osmosis will generally remove salt, manganese, iron, fluoride, lead, and calcium (Binnie et. al., 2002). Most mineral constituents of water are physically larger than water molecules and they are trapped by the semi-permeable membrane and removed from drinking water when filtered through an RO system (AllAboutWater.org, 2004). Meanwhile, consumers are concerned about the removal of minerals from their drinking water.
Reverse Osmosis (RO) removed 90-99.99% of all the contaminants including minerals from the drinking water supply (see Figure 1). RO removes minerals because they have larger molecules than water. The subject of minerals and RO created controversy and disagreement among water and health professionals. The World Health Organization (WHO) made clarification that majority of healthy minerals are needed for human body is from food or dietary supplementary sources and not from drinking tap water. In addition, minerals found in water can be harmful to human health. The evidence is strong that calcium and magnesium are essential elements for human body (WQA, 2011). However, its a weak argument to suggest that we should make up this deficiency through water consumption (WQA, 2011). Tap water presents a variety of inorganic minerals which the human body has difficulty absorbing (Misner, 2004). Their presence is suspect in a wide array of degenerative diseases, such as hardening of the arteries, arthritis, kidney stones, gall stones, glaucoma, cataracts, hearing loss, emphysema, diabetes, and obesity. What minerals are available, especially in “hard” tap water, are poorly absorbed, or rejected by cellular tissue sites, and, if not evacuated, their presence may cause arterial obstruction, and internal damage (Dennison, 193; Muehling, 1994; Banik, 1989).
Figure 1. Reverse Osmosis Membrane (Source:DOI-BUR, 2009)
Organic Minerals vs. Inorganic Minerals
There are two types of minerals in water, organic and inorganic. Human physiology has a biological affinity for organic minerals. Most organic minerals for our body functions come from dietary plant foods (Misner, 2004). A growing plant converts the inorganic minerals from the soils to a useful organic mineral (Misner, 2004). When an organic mineral (from a plant food) enters the stomach it must attach itself to a specific protein-molecule (chelation) in order to be absorbed, then it gains access to the tissue sites where it is needed (Misner, 2004). Once a plant mineral is divested within the body, it is utilized as a coenzyme for composing body fluids, forming blood and bone cells, and the maintaining of healthy nerve transmission (Balch & Balch 1990).
Reverse Osmosis has Little Effect on Water pH
Water pH levels will automatically change when water is ingested and comes into contact with the food in your stomach (Wise, 2011). Even on an empty stomach, your stomach acid alone is already several times more acidic than RO water (pH 6-8) with a pH level of 2 (Wise, 2011). The human body regulates pH levels constantly to find balance and equilibrium (see Figure 2). Therefore under normal conditions it will always maintain a neutral 7.4 pH balance (Wise, 2011). The healthy body is very robust and it will restore homeostatic pH fairly quickly and easily (Wise 2011). Soft drinks and sports drinks typically have a pH level of 2.5, orange juice has a 3 pH and coffee has a 4 pH level and we drink these beverages all the time without problems (Wise, 2011).
Figure 2. Comparison of pH Levels (Source: Wise, 2011)
Water filtered or treated by reverse osmosis is generally pure, clean, and healthy. A reverse osmosis treatment system is currently the only technology that can remove most of the emerging contaminants (i.e., prescription drugs and perchlorate) including other contaminants (i.e., arsenic, cyanide, and fluoride) that are difficult to remove by other treatment methods. No more ingesting of harmful inorganic minerals means the body will no longer be stressed with trying to absorb something that wasn’t supposed to be there in the first place (Wise, 2011). Consumers should not be concerned about the removal of minerals by RO system. As the WHO (2009) and WQA (2011) pointed out, the human body obtains the vast majority of minerals from food or supplements, not from drinking water.
One of the downsides to the reverse osmosis process is that it is so effective in removing particles, it will also remove minerals from your water that may be beneficial. The body needs certain minerals, such as calcium and magnesium, to function properly. In addition, some people believe minerals such as this actually add flavor to the water, so that will be missing if you filter the water. Some find a certain acidic taste to water that has been purified by reverse osmosis. A reverse osmosis system also wastes a certain amount of water. For every gallon of purified water, three or four gallons have to be processed. If water is scarce or expensive in your area, this is a strong consideration.
The Myron L RO-1 was developed years ago specifically for Culligan, and is designed for testing RO systems.
The choice of professionals for years, this compact instrument has been designed specifically to demonstrate and test Point of Use (POU) reverse osmosis or distillation systems. By measuring electrical conductivity, it will quickly determine the parts per million/Total Dissolved Solids (ppm/TDS) of any drinking water.
With a single ‘before and after’ test, this handy device effectively demonstrates how your RO or distillation system eliminates harmful dissolved solids. It will also service test systems, including membrane evaluation programs. Find out more about the RO-1 meter HERE.
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.
- J. M. M. Matos, Evaluation of pH test on exudate check feasibility of forest seeds, dissertation, University of Brasília, Brasília, Brazil, 2009.
- F. Poggiani, S. Bruni, and E. S. Q. Barbos, “Effect of shading on seedling growth of three species forest,” in National conference on native plants, vol. 2, pp. 564–569, Institute of Forestry, 1992.
- M. B. Mcdonald Jr. and D. O. Wilson, “ASA-610 ability to detect changes in soybean seed quality,” Journal of Seed Technology, vol. 5, no. 1, pp. 56–66, 1980.
- S. Matthews and A. Powell, “A eletrical conductivity test,” in Handbook of Vigor Test Methods, D. A. Perry, Ed., pp. 37–42, International Seed Testing Associaty, Zurich, Switzerland, 1981.
- J. Son Mark, W. R. Singh, A. D. C. Novembre, and H. M. C. P. Chamma, “Comparative studies to evaluate dem’etodos physiological quality of soybean seeds, with emphasis the electrical conductivity test,” Brazilian Journal of Agricultural Research, vol. 25, no. 12, pp. 1805–1815, 1990.
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- J. M. Felfili, C. W. Fagg, J. C. S. Silva, et al., Plants of the APA Gama Cabeça de Veado: Species, ecosystems and recovery, University of Brasilia, Brasília, Department of Engineering Forest, Brasília, Brazil, 2002.
- M. F. B. Muniz, et al., “Comparison of methods for evaluating the physiological and health quality of melon seeds,” Journal of Seeds, Pellets, vol. 26, no. 2, pp. 144–149, 2004.
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- R. D. Vieira, “Electrical conductivity test,” in Seed Vigor Tests, R. D. Vieira and N. M. Carvalho, Eds., p. 103, FUNEP, Jaboticabal, Brazil, 1994.
- A. S. Amaral and S. T. Peske, “Exudate pH to estimate, in 30 minutes seed viability of soybeans,”Journal of seeds, vol. 6, no. 3, pp. 85–92, 1984.
- E. J. Fernandes, R. Sader, and N. M. Carvalho, “seed viability beans (Phaseolus vulgaris L.) estimated by the pH of the exudate,” in Congress Brazil’s Seeds, Gramado, Brazil, 1987.
- F. C. Krzyzanowski and R. D. Vieira, “Electrical conductivity test,” in Seed Vigor: Concepts and Tests, F. C. Krzyzanowski, R. D. Vieira, and J. B. France Neto, Eds., pp. 4.1–4.26, Abrates, London, UK, 1999.
- Ministry of Agriculture, Livestock and Supply, Rule for seed testing, SNPA/DNPV/CLAV, Brasilia, Brazil, 1992.
- Ministry of Agriculture, Livestock and Supply, Rule for seed testing, SNPA/DNPV/CLAV, Brasilia, Brazil, 2009.
- N. M. Carvalho and J. Nakagawa, Seeds: Science, Technology and Production, FUNEP, Jaboticabal, Brazil, 2000.
- Pina-Rodrigues, et al., “Quality test,” in Germination from Basic to Applied, A. Ferreira and G. F. Borghetti, Eds., pp. 283–297, 2004.
- A. G. Ferreira and F. Borghetti, from basic to Germination applied, Artmed, Porto Alegre, Brazil, 2004.
- L. G. Labouriau, seed germination, OAS, Washington, DC, USA, 1983.
- 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.
TweetHypothesis: Does the time of year affect the conductivity of stagnant water in a given location? Abstract: We decided to test the conductivity levels of the water at Flat Rock Brook. If the conductivity levels are higher, it might imply higher total dissolved solid levels. We would like to see if the conductivity level changes during seasons […]
Hypothesis: Does the time of year affect the conductivity of stagnant water in a given location? Abstract: We decided to test the conductivity levels of the water at Flat Rock Brook. If the conductivity levels are higher, it might imply higher total dissolved solid levels. We would like to see if the conductivity level changes during seasons with snowfall versus seasons without snowfall. Background:
- Independent Variable: Time of Year (Season)
- Independent Variable: Location
- Dependent Variable: Conductivity Level (mg/L TDS)
The purpose of the experiment is to test the change in conductivity level throughout the year (on a seasonal basis) in various locations. While doing this experiment, it is important to keep in mind these three things:
- How does conductivity vary at any of the given sites during a given season.(1)
- What human influence might have an impact on the conductivity of the water at any given part of the year.(1)
- Why might this change affect the ability of organisms to live in the given test sites.(1)
This is important to Flat Rock Brook because the data could be used to do several things. For example, the change in conductivity may change the organic life in the water, thus changing the ability to safely drink it. The change may impact the ability of organisms to grow in the water, and it may change the reactive nature of the water. Conductivity can be measured by the total dissolved solids in the water. Total Dissolves Solids include the number of mineral and salt impurities in the water. (1) Ultimately, the number of minerals and salts determines how many ions in mg/L. The impurities in the water can include runoff from roads, wastewater from industrial plants, and soils and rocks. (1) The amount of total dissolved solids in the water can have a physiological effect on plants and animals living in the ponds. (2) Conductivity can be used as a way of noting changes in water conditions over short periods of time. (2) Also, the level of total dissolved solvents in water can have an effect of the ability of habitat-forming plants to grow, thus disrupting the presence of certain species. (2) Materials:
- GPS Navigator by Magellan: We used the GPS as a way to mark off specific testing sites at McFadden’s Pond and Quarry Pond, in order to test in a precise and consistent location
- pH/Conductivity Probe: We used the pH/Conductivity Probe to test the level of conductivity in the various locations. The conductivity was measured in mg/L (TDS), and microsiemens (µS), but due to the difficult nature of working with microsiemens, we chose to work primarily with mg/L(TDS).
- Distilled Water: We used the distilled water to wash off the probe in between tests in order to maintain accurate readings without tainted results.
- Map of Flat Rock Brook: We used the map of Flat Rock Brook in order to find locations from which we could test conductivity levels of water.
- Vernier conductivity probe used with a Lab Pro interface: We used this for our May data in order to get a more accurate reading. By taking samples from Flat Rock Brook, we connected this probe to Logger Pro and recorded the conductivity which was also measured in TDS. NOTE: We used the conductivity data from these readings in our graphs and overall analysis because it provided a more accurate measurement
Methods: *Adapted from Electrical Conductivity Protocol Used by University Corporation for Atmospheric Research, Colorado State University, and NASA. (Water Temperature was not recorded.)
- Record water temperature
- Pour water sample into two containers (or measure in water body)
- Rinse electrodes with distilled water, blot dry
- Place meter in first container, 2-3 seconds
- Remove meter, shake gently, and place in second
container, 1 minute (Do not rinse with distilled water)
- Record value when stabilized
- Repeat measurement with new sample water, twice
- Average three measurements and check for accuracy
Original Protocol can be found at this link*: http://18.104.22.168/search?q=cache:tpTXJUjpiHgJ:globe.ucar.edu/trr-
Cleaning off the conductivity probe before testing the water. (Figure 2)
Testing the conductivity of the pond (Figure 3)
Results: Fall (November) : -Quarry Pond:
- .9 mg/L
-McFadden’s Pond (site A)*:
- 3.1 mg/L
-McFadden’s Pond (site B)*:
- 3.05 mg/L
Spring (May): (with ph/conductivity probe) -Quarry Pond:
- .83 mg/L
-McFadden’s Pond (Site A):
- 2.95 mg/L
-McFadden’s Pond (Site B):
- 2.02 mg/L
Spring (May): (LoggerPro Data) -Quarry Pond:
- .8 mg/L
-McFadden’s Pond (Site A):
- 3.1 mg/L
-McFadden’s Pond (Site B):
- 2.1 mg/L
Data Graph for Quarry Pond (Figure 4)
Data Graph for McFadden’s Pond Site A (Figure 5)
Data Graph for McFadden’s Pond Site B (Figure 6)
Data Graph for all three locations (Figure 7)
Discussion: Throughout our research, there was a general shift in the conductivity level in each site we tested. At Quarry Pond, the total dissolved solids reduced from .9 mg/L to .8 mg/L from November to May. This shift can be seen in the graph shown in Figure 4. McFadden’s Pond Site B also showed a substantial shift between the November and May readings, from 3.05 mg/L to 2.1 mg/L, as seen in Figure 6. Despite these significant changes, Site A at McFadden’s Pond did not change. This could potentially be due to its close proximity to moving water. A subtle, unnoticed under-current may have existed which may have caused the water to be mixed, and therefore diluted. The figures for this measurement can be seen in Figure 5.
The changes in conductivity at Quarry Pond may be the result of runoff from the parking lot and the roads in close proximity to it. Quarry Pond, unlike the other locations was close enough to a road that run-off affects the level of total dissolved solids. Although there was a significant change in conductivity between readings, the total dissolved solids were much lower than that of McFadden’s Pond. This may explain why the presence of algae was much higher in Quarry Pond than in McFadden’s Pond. McFadden’s Pond’s conductivity may have been higher due to a larger level of mineral deposits from soil runoff. One possible explanation for this shift in conductivity is the dilution of total dissolved solids in pond water due to rainfall and melting water from snow.
Conclusion: When comparing conductivity of water at a given point of time during the year, it is clear that there are noticeable differences. During the Fall and Winter, when there is more soil and road runoff, the conductivity level is higher. Conversely, during the spring, when there is more rainwater and melted snow and ice to dilute the ponds, the conductivity level drops. This would suggest that during fall and winter, the conditions of the pond are noticeably different. This suggests the possibility that there may be a shift in population from one group of organisms to another on a seasonal basis. Knowledge of these changes may help to explain why animals would migrate to a different habitat during different seasons. Because of the nature of soil runoff and road runoff, the level of Total Dissolved Solids in the water changes on a seasonal basis, and with that, the conductivity changes as well. In conclusion, conductivity does change over time of year in stagnant water, primarily because of external conditions such as runoff and wastewater.
(1)The GLOBE Program, “Electrical Conductivity Protocol.” Hydro-Electrical Conductivity. Ed. UCAR, Colorado State University, NASA.
We used the Power Point file linked to this page as our primary source of background information as well as a standard protocol for our field tests.
(2)Conductivity And Water Quality.
<[[http://kywater.org/ww/ramp/rmcond.htm%3C/span%3E%3Cspan|http://kywater.org/ww/ramp/rmcond.htm<span]] We used this website as our second source of data for finding out environmental impacts of change in conductivity and overall water quality. (Note: No Author, Publisher or Editor could be found for this web page.) __ *Site A is to the right of Mystery Bridge *Site B is to the left of Mystery Bridge *Note, this protocol was implemented both in the field and in a lab dependent on the time the data was collected *If the web page is difficult to view, a link to a .ppt file is available at the top of the page. The protocol can be found on slide #12.
Study authors: Margot Bennett and Rob Schwartz
Contributions to http://d-e-science11.wikispaces.com/ are licensed under a Creative Commons Attribution Share-Alike 3.0 License
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