Science and Industry Updates
Tweet For Pool Professionals The PoolPro is a comprehensive high performance tool designed to simplify pool and spa water quality control for the pool professional. Both PoolPro models – the PS6 and the PS9TK feature innovative user-friendly features and functions that make […]
For Pool Professionals
The PoolPro is a comprehensive high performance tool designed to simplify pool and spa water quality control for the pool professional. Both PoolPro models – the PS6 and the PS9TK feature innovative user-friendly features and functions that make it easy to manage parameters critical to disinfection, water balance, system maintenance and compliance.
New! Fce FAC Readings
FCE function reports FAC quickly and accurately by measuring ORP, the chemical characteristic of chlorine that directly reflects its effectiveness, cross referenced with pH. Both DPD kits and colorimeters may tell the user the FAC value of the sample in the test tube, but since the chemistry of that sample is quite different from the source water being analyzed, the results are imprecisely related to actual disinfection power.
FCE function measures the real, unaltered chemistry of source water, including moment-to-moment changes in that chemistry.
FCE can be used for other types of oxidizing germicides and will track the effect of additives, such as cyanuric acid, that degrade chlorine effectively without changing the actual concentration of free available chlorine present.
In-Cell Titration Functions
The PS9TK adds the ability to perform in-cell conductometric titrations that provides a convenient way to determine alkalinity, hardness and LSI in the field. This eliminates the need to collect and transport samples to another location for analysis. User intuitive display prompts guide you through titration procedures from start to finish. All required reagents and equipment are included in the PS9 titration kit.
Water Balance Analysis
The PS9TK features both an LSI Calculator and an LSI Titration measurement mode. The Calculator allows you to perform what-if scenarios to predict how changes in solution parameters would affect the water balance of a system. The titration measurement function allows you to accurately calculate a saturation index value of a specific solution to determine whether the solution is balanced, scaling or corrosive.
Hardness Unit Conversion The Hardness and LSI Titrations and LSI Calculator functions allow you to set the hardness unit preference to either grains of hardness or ppm CaCO3 according to your needs.
System Validation & Calibration
The PoolPro provides a fast, precise, easy-to-use method of obtaining Oxidation Reduction Potential (ORP or REDOX) mV readings to check the true level of effectiveness of ALL sanitizers in any pool or spa. ORP objectively and precisely measures sanitizer ability to burn up, or oxidize, organic matter in the water. ORP can only be determined by an electronic instrument.
PoolPro ORP mV readings serve as a necessary check to ensure automatic ORP control systems are working properly. PoolPro also provides independent readings for recalibration and to detect system failure.
Saltwater Chlorine Generation
PoolPro provides a convenient one-touch test for Mineral/Salt concentration. This is ideal for saltwater systems where manual testing with separate instrumentation is necessary to ensure the proper amount of sodium chloride is present for chlorine generation in quantities specified for microbial disinfection. PoolPro can also be used to recalibrate equipment as part of regular maintenance.
The optional bluDock™ accessory package is an integrated data solution for your record keeping requirements, eliminating the need for additional hardware, wires and hassle. Because the user never touches the data, there is little opportunity for data tampering and human error. bluDock software has an easy to use interface with user intuitive functions for storing, sorting and exporting data.
Simply the Best
PoolPro is lightweight, portable, buoyant, waterproof, easy-to-calibrate, and easy-to-use. Simply rinse and fill the cell cup by dipping the PoolPro in the water, then press the button of the parameter you wish to measure. You immediately get a standard, numerical digital readout — eliminating all subjectivity. And you can store up to 100 date-time-stamped readings in PoolPro’s non-volatile memory.
Watch for the product launch later this year.
TweetRecent Papers in Water Treatment for Small/Decentralized Systems Content Table Recent Papers in Water Treatment for Small/Decentralized Systems Turbidity and chlorine demand reduction using locally available physical water clarification mechanisms before household chlorination in developing countries Appropriate wastewater treatment systems for developing countries: criteria and indictor assessment in Thailand A new paradigm for low-cost urban […]
Recent Papers in Water Treatment for Small/Decentralized Systems
- Recent Papers in Water Treatment for Small/Decentralized Systems
- Turbidity and chlorine demand reduction using locally available physical water clarification mechanisms before household chlorination in developing countries
- Appropriate wastewater treatment systems for developing countries: criteria and indictor assessment in Thailand
- A new paradigm for low-cost urban water supplies and sanitation in developing countries
- Faecal bacterial indicators removal in various wastewater treatment plants located in Almendares River watershed (Cuba)
- Treatment of low and medium strength sewage in a lab-scale gradual concentric chambers (GCC) reactor
- Use of modelling for optimization and upgrade of a tropical wastewater treatment plant in a developing country
- Ceramic silver-impregnated pot filters for household drinking water treatment in developing countries: material characterization and performance study
- Ceramic membranes for direct river water treatment applying coagulation and microfiltration
- Related Publications
Turbidity and chlorine demand reduction using locally available physical water clarification mechanisms before household chlorination in developing countries
Journal of Water and Health Vol 07 No 3 pp 497–506 © IWA Publishing 2009 doi:10.2166/wh.2009.071
Nadine Kotlarz, Daniele Lantagne, Kelsey Preston and Kristen Jellison
Department of Civil and Environmental Engineering, Lehigh University, 13 East Packer Avenue, Bethlehem, PA 18015, USA
Enteric Diseases Epidemiology Branch, US Centers for Disease Control and Prevention, 1600 Clifton Road, MS-A38, Atlanta, GA 30333, USA Tel.: +1 404 639 0231 Fax: +1 404 639 2205 E-mail: firstname.lastname@example.org
Over 1.1 billion people in the world lack access to improved drinking water. Diarrhoeal and other waterborne diseases cause an estimated 1.9 million deaths per year. The Safe Water System (SWS) is a proven household water treatment intervention that reduces diarrhoeal disease incidence among users in developing countries. Turbid waters pose a particular challenge to implementation of SWS programmes; although research shows that a 3.75 mg l-1 sodium hypochlorite dose effectively treats turbid waters, users sometimes object to the strong chlorine taste and prefer to drink water that is more aesthetically pleasing. This study investigated the efficacy of three locally available water clarification mechanisms—cloth filtration, settling/decanting and sand filtration—to reduce turbidity and chlorine demand at turbidities of 10, 30, 70, 100 and 300 NTU. All three mechanisms reduced turbidity (cloth filtration -1–60%, settling/decanting 78–88% and sand filtration 57–99%). Sand filtration (P=0.002) and settling/decanting (P=0.004), but not cloth filtration (P=0.30), were effective at reducing chlorine demand compared with controls. Recommendations for implementing organizations based on these results are discussed.
Appropriate wastewater treatment systems for developing countries: criteria and indictor assessment in Thailand
Water Science & Technology—WST Vol 59 No 9 pp 1873–1884 © IWA Publishing 2009 doi:10.2166/wst.2009.215
W. Singhirunnusorn and M. K. Stenstrom
Faculty of Environment and Resource Studies, Mahasarakham University, Kantharawichai District, Maha Sarakham Province 44150, Thailand E-mail: email@example.com
Department of Civil and Environmental Engineering, UCLA, Los Angeles CA 90095, USA E-mail: firstname.lastname@example.org
This paper presents a comprehensive approach with factors to select appropriate wastewater treatment systems in developing countries in general and Thailand in particular. Instead of focusing merely on the technical dimensions, the study integrates the social, economic, and environmental concerns to develop a set of criteria and indicators (C&I) useful for evaluating appropriate system alternatives. The paper identifies seven elements crucial for technical selection: reliability, simplicity, efficiency, land requirement, affordability, social acceptability, and sustainability. Variables are organized into three hierarchical elements, namely: principles, criteria, and indicators. The study utilizes a mail survey to obtain information from Thai experts—academicians, practitioners, and government officials—to evaluate the C&I list. Responses were received from 33 experts on two multi-criteria analysis inquiries—ranking and rating—to obtain evaluative judgments. Results show that reliability, affordability, and efficiency are among the most important elements, followed by sustainability and social acceptability. Land requirement and simplicity are low in priority with relatively inferior weighting. A number of criteria are then developed to match the contextual environment of each particular condition. A total of 14 criteria are identified which comprised 64 indicators. Unimportant criteria and indicators are discarded after careful consideration, since some of the indicators are local or site specific.
A new paradigm for low-cost urban water supplies and sanitation in developing countries
Water Policy Vol 10 No 2 pp 119–129 © IWA Publishing 2008 doi:10.2166/wp.2008.034
Duncan Maraa and Graham Alabasterb
aCorresponding author. School of Civil Engineering, University of Leeds, Leeds LS2 9JT UK. Fax: +44-113-343-2243 E-mail: email@example.com
bUnited Nations Human Settlements Programme, PO Box 30300, Nairobi, Kenya
To achieve the Millennium Development Goals for urban water supply and sanitation ~300,000 and ~400,000 people will have to be provided with an adequate water supply and adequate sanitation, respectively, every day during 2001–2015. The provision of urban water supply and sanitation services for these numbers of people necessitates action not only on an unprecedented scale, but also in a radically new way as “more of the same” is unlikely to achieve these goals. A “new paradigm” is proposed for low-cost urban water supply and sanitation, as follows: water supply and sanitation provision in urban areas and large villages should be to groups of households, not to individual households. Groups of households would form (even be required to form, or pay more if they do not) water and sanitation cooperatives. There would be standpipe and yard-tap cooperatives served by community-managed sanitation blocks, on-site sanitation systems or condominial sewerage, depending on space availability and costs and, for non-poor households, in-house multiple-tap cooperatives served by condominial sewerage or, in low-density areas, by septic tanks with on-site effluent disposal. Very poor households (those unable to afford to form standpipe cooperatives) would be served by community-managed standpipes and sanitation blocks.
Faecal bacterial indicators removal in various wastewater treatment plants located in Almendares River watershed (Cuba)
Water Science & Technology—WST Vol 58 No 4 pp 773–779 © IWA Publishing 2008 doi:10.2166/wst.2008.440
Tamara Garcia-Armisen, Josué Prats, Yociel Marrero and Pierre Servais
Ecologie des Systèmes Aquatiques, Université Libre de Bruxelles, Brussels, Belgium *Present address: MINT, Vrije Universiteit Brussel, Building E, Pleinlaan 2, 1050, Brussels, Belgium Tel.: +3226291918 E-mail: firstname.lastname@example.org
Dpto. de Microbiología, Facultad de Biología, Universidad de La Habana, La Habana, Cuba
Instituto Superior Politécnico José Antonio Echeverría, La Habana, Cuba
The Almendares River, located in Havana city, receives the wastewaters of more than 200,000 inhabitants. The high abundance of faecal bacterial indicators (FBIs) in the downstream stretch of the river reflects the very poor microbiological water quality. In this zone, the Almendares water is used for irrigation of urban agriculture and recreational activities although the microbiological standards for these uses are not met. Improvement of wastewater treatment is absolutely required to protect the population against health risk. This paper compares the removal of FBIs in three wastewater treatment plants (WWTPs) located in this watershed: a conventional facility using trickling filters, a constructed wetland (CW) and a solar aquatic system (SAS). The results indicate better removal efficiency in the two natural systems (CW and SAS) for all the measured parameters (suspended matters, biological oxygen demand, total coliforms, E. coli and enterococci). Removals of the FBIs were around two log units higher in both natural systems than in the conventional one. A longitudinal profile of the microbiological quality of the river illustrates the negative impact of the large conventional WWTP. This case study confirms the usefulness of small and natural WWTPs for tropical developing countries, even in urban and periurban areas.
Treatment of low and medium strength sewage in a lab-scale gradual concentric chambers (GCC) reactor
Water Science & Technology—WST Vol 57 No 8 pp 1155–1160 © IWA Publishing 2008 doi:10.2166/wst.2008.093
L. Mendoza, M. Carballa, L. Zhang and W. Verstraete
Experimental Reproduction Centre (CEYSA), Agricultural Faculty, Technical University of Cotopaxi, Latacunga, Ecuador E-mail: email@example.com
Laboratory of Microbial Ecology and Technology (LabMET), Ghent University, Coupure Links 653, B-9000, Ghent, Belgium E-mail: firstname.lastname@example.org; email@example.com; firstname.lastname@example.org
One of the major challenges of anaerobic technology is its applicability for low strength wastewaters, such as sewage. The lab-scale design and performance of a novel Gradual Concentric Chambers (GCC) reactor treating low (165±24 mg COD/L) and medium strength (550 mg COD/L) domestic wastewaters were studied. Experimental data were collected to evaluate the influence of chemical oxygen demand (COD) concentrations in the influent and the hydraulic retention time (HRT) on the performance of the GCC reactor. Two reactors (R1 and R2), integrating anaerobic and aerobic processes, were studied at ambient (26°C) and mesophilic (35°C) temperature, respectively. The highest COD removal efficiency (94%) was obtained when treating medium strength wastewater at an organic loading rate (OLR) of 1.9 g COD/L·d (HRT = 4 h). The COD levels in the final effluent were around 36 mg/L. For the low strength domestic wastewater, a highest removal efficiency of 85% was observed, producing a final effluent with 22 mg COD/L. Changes in the nutrient concentration levels were followed for both reactors.
Use of modelling for optimization and upgrade of a tropical wastewater treatment plant in a developing country
Water Science & Technology Vol 56 No 7 pp 21–31 © IWA Publishing 2007 doi:10.2166/wst.2007.675
D. Brdjanovic*, M. Mithaiwala** , M.S. Moussa*** , G. Amy* and M.C.M. van Loosdrecht****
*Department of Urban Water and Sanitation, UNESCO-IHE Institute for Water Education, Westvest 7, PO Box 3015, 2061 DA , Delft, The Netherlands (E-mail: email@example.com)
**Drainage Department, Surat Municipal Corporation, Muglisara, Surat , Gujarat, 395003, India (Email: firstname.lastname@example.org)
***Civil Engineering Department, Faculty of Engineering Mataria, Helwan , University, Egypt (Email: email@example.com)
****Department of Biochemical Engineering, Delft University of Technology, Julianalaan 67, 2628 BC , Delft, The Netherlands (Email: firstname.lastname@example.org)
This paper presents results of a novel application of coupling the Activated Sludge Model No. 3 (ASM3) and the Anaerobic Digestion Model No.1 (ADM1) to assess a tropical wastewater treatment plant in a developing country (Surat, India). In general, the coupled model was very capable of predicting current plant operation. The model proved to be a useful tool in investigating various scenarios for optimising treatment performance under present conditions and examination of upgrade options to meet stricter and upcoming effluent discharge criteria regarding N removal. It appears that use of plant-wide modelling of wastewater treatment plants is a promising approach towards addressing often complex interactions within the plant itself. It can also create an enabling environment for the implementations of the novel side processes for treatment of nutrient-rich, side-streams (reject water) from sludge treatment.
Ceramic silver-impregnated pot filters for household drinking water treatment in developing countries: material characterization and performance study
Water Science & Technology: Water Supply Vol 7 No 5-6 pp 9–17 © IWA Publishing 2007 doi:10.2166/ws.2007.142
D. van Halem*, S.G.J. Heijman* , A.I.A. Soppe** , J.C. van Dijk* and G.L. Amy***
*Delft University of Technology, Stevinweg 1, 2628 CN , Delft, The Netherlands (E-mail: email@example.com; firstname.lastname@example.org)
**Delft University of Technology & Kiwa Water Research, Groningenhaven 7, 3433 PE , Nieuwegein, The Netherlands (E-mail: email@example.com)
***Aqua for All Foundation, Groningenhaven 7, 3433 PE , Nieuwegein, The Netherlands (E-mail: firstname.lastname@example.org)
****UNESCO-IHE Institute for Water Education, Westvest 7, 2611 AX , Delft, The Netherlands (E-mail: email@example.com)
The ceramic silver-impregnated pot filter (CSF) is a low-cost drinking water treatment system currently produced in many factories worldwide. The objective of this study is to gather performance data to provide a scientific basis for organisations to safely scale-up and implement the CSF technology. Filters from three production locations are included in this study: Cambodia, Ghana and Nicaragua. The microstructure of the filter material was studied using mercury intrusion porosimetry and bubble-point tests. Effective pores were measured with a mean of 40 mm, which is larger than many pathogenic microorganisms. The removal efficiency of these microorganisms was measured by using indicator organisms; total coliforms naturally present in canal water, sulphite reducing Clostridium spores, E.coli K12 and MS2 bacteriophages. The removal of these organisms was monitored during a long-term study of several months in the laboratory. Ceramic silver impregnated pot filters successfully removed total coliforms and sulphite reducing Clostridium spores. High concentrations of Escherichia coli K12 were also removed, with log(10) reduction values consistently higher than 2. MS2 bacteriophages were only partially removed from the water, with significantly better results for filters without an impregnation of colloidal silver. During this study the main deficiency of the filter system proved to be the low water production; after 12 weeks of use all filter discharges were below 0.5 Lh-1, which is insufficient to provide drinking water for a family
Ceramic membranes for direct river water treatment applying coagulation and microfiltration
Water Science & Technology: Water Supply Vol 6 No 4 pp 89–98 © IWA Publishing 2006 doi:10.2166/ws.2006.906
A. Loi-Brügger*, S. Panglisch*, P. Buchta*, K. Hattori**, H. Yonekawa**, Y. Tomita** and R. Gimbel*,***
*IWW Water Center, Moritzstr. 26, 45476 Mülheim, , Germany (E-mail: firstname.lastname@example.org)
**NGK Insulators Ltd., 2-56 Suda-cho, Nagoya, Aichi, , 467-8530, Japan (E-mail: email@example.com)
***Institut für Energie- und Umweltverfahrenstechnik, Universität Duisburg-Essen Bismarckstr. 90, 47057 Duisburg, , Germany (E-mail: firstname.lastname@example.org)
A new ceramic membrane has been designed by NGK Insulators Ltd., Japan, to compete in the drinking water treatment market. The IWW Water Centre, Germany, investigated the operational performance and economical feasibility of this ceramic membrane in a one year pilot study of direct river water treatment with the hybrid process of coagulation and microfiltration. The aim of this study was to investigate flux, recovery, and DOC retention performance and to determine optimum operating conditions of NGK’s ceramic membrane filtration system with special regards to economical aspects. Temporarily, the performance of the ceramic membrane was challenged under adverse conditions. During pilot plant operation river water with turbidities between 3 and 100 FNU was treated. Membrane flux was increased stepwise from 80–300 l/m2h resulting in recoveries between 95.9 and 98.9%. A DOC removal between about 20–35% was achieved. The pilot study and the subsequent economical evaluation showed the potential to provide a reliable and cost competitive process option for water treatment. The robustness of the ceramic membrane filtration process makes it attractive for a broad range of water treatment applications and, due to low maintenance requirements, also suitable for drinking water treatment in developing countries.
Public Private Partnerships in the Water Sector – Cledan Mandri-Perrott and David Stiggers
Publication Date: Mar 2013 – ISBN – 9781843393207
Designing Wastewater Systems According to Local Conditions – David M Robbins
Publication Date: Jan 2014 – ISBN – 9781780404769
Water Services Management and Governance – Tapio Katko, Petri S. Juuti, and Klaas Schwartz
Publication Date: Oct 2012 – ISBN – 9781780400228
Meeting the Challenge of Financing Water and Sanitation – Organisation for Economic Co-Operation and Development (OECD)
Publication Date: Nov 2011 – ISBN – 9781780400327
OECD Water Resources and Sanitation Set – Organisation for Economic Co-Operation and Development (OECD)
Publication Date: Nov 2011 – ISBN – 9781780400570
Reverse osmosis biofouling: Impact of feed channel spacer and biofilm development in spacer-filled channels – MyronLMeters.com
TweetIntroduction Water desalination via reverse osmosis (RO) technology provides a solution to the world’s water shortage problem. Until now, the production of fresh water from seawater has reached 21-million cubic meter per day all around the world (Wangnick, 2005). However, the success of RO technology is subject to improvement as the technology is challenged by […]
Water desalination via reverse osmosis (RO) technology provides a solution to the world’s water shortage problem. Until now, the production of fresh water from seawater has reached 21-million cubic meter per day all around the world (Wangnick, 2005). However, the success of RO technology is subject to improvement as the technology is challenged by a biofouling problem –a problem related to biological material development which forms a sticky layer on the membrane surface (Flemming, 1997; Baker and Dudley, 1998).
Continuous biofouling problems in RO lead to higher energy input requirement as an effect of increased biofilm resistance (Rf) and biofilm enhanced osmotic pressure (BEOP), lower quality of product water due to concentration polarization (CP) – increased concentration due to solutes accumulation on the membrane surface, (Herzberg and Elimelech, 2007), and thus significant increase in both operating and maintenance costs.
Recent studies and objectives
Recent studies show the importance of the operating conditions (e.g. flux and cross flow velocities) in RO biofouling. The presence of feed channel spacers has also been getting more attention as it may have adverse effects. A previous study (Chong et al., 2008) without feed channel spacers showed that RO biofouling was a flux driven process where higher flux increased fouling rate. It was also shown that biofouling caused a BEOP effect due to elevated CP of solutes at the membrane surface, thus resulted in loss of driving force. The BEOP effect was more severe at high flux and low crossflow operation.
In another recent study (Vrouwenvelder et al., 2009a) involving feed channel spacers suggested that flux did not affect fouling and biofouling was more severe when the crossflow velocity was higher. However, these studies were conducted on river water at low level of salinity and under no/very low flux conditions, which may suggested that BEOP effect was not observed in the above studies. These contradictory observations relating to the biofouling process in RO need to be systematically addressed as it is critical to understand the mechanism for sustainable operation of RO technology.
The objective of this study was to observe the impact of spacer towards RO biofouling as well as to investigate the development of biofilm in a spacer filled channel. The experiments were conducted at constant flux and biofouling was observed by the increase of transmembrane pressure (TMP). Observation with confocal light scanning microscope (CLSM) method was conducted to the fouled membrane and spacers to provide information of biofilm development inside the membrane module.
Materials and methods
A lab-scale set-up was arranged to resemble the real RO operation where experiments were performed with elevated salinity, high pressure, imposed flux, and permeation. The schematic diagram of the set-up is depicted in Figure 1. It is a fully-recycled system with two identical RO modules running in series. Feed solution contained constant amounts NaCl and nutrient broth (NB) to provide sufficient TOC level.
The study was conducted in the constant flux mode and biofouling was measured via the rise in TMP. A mass-flow controller was installed at the permeate side to maintain the amount of permeate withdrawn. A bacteria solution was injected into the system before the feed solution entered the RO modules and a set of microfilters (5 μm and 0.2 μm) were installed at downstream to prevent excess bacteria from entering the feed tank and turning the feed tank into an “active bioreactor”.
Model bacteria Pseudomonas aeruginosa (PAO1) was used in the experiment. Bacteria stock solution used in the biofouling tests was prepared in batch and the stock solution was replenished every 24 hours. Bacteria were grown in mixture of NB and NaCl solution where they were harvested after 24 hours and diluted into autoclaved salt solution. The concentration of bacteria was controlled and measured by optical density (OD) using UV spectrophotometer at 600 nm. Batch prepared bacteria stock solution has some advantages over using continuous feed from a chemostat (Chong et al., 2008). A more consistent and fresh bacteria load and without excess nutrient was introduced into the system as nutrient content was completely removed in the harvesting step.
Prior to every experiment, cut RO membranes (DOW Filmtec, BW-30) were soaked in Milli-Q water and sterilized in 70% ethanol solution. Similar pretreatment procedures were applied to membrane support layers and feed channel spacers prior every experiment. The spacers used in the experiments are obtained from unused Hydranautics LFC-1 spiral wound module (Figure 2).
The membranes were compacted at a maximum flux (~65 L/m2.h) overnight with Milli-Q water until a stable flux was achieved. Following compaction, the flux was set to the desired values and NaCl solution was added into the feed tank until the desired concentration was achieved. The system was let to mix for 1.5 hours. NB solution was then added into the feed tank to provide an average background nutrient concentration of 6.5 mg/L TOC. The system was allowed to well-mix for 1.5 hours.
The biofouling test was initiated by continuous injection of bacteria stock solution into the flow line at a dilution rate of 1:500 based on RO cross-flow rate. Biofilm was allowed to grow on the RO membranes. TMP rise due to biofouling was measured over time. The solution in the feed tank was removed and replaced with a fresh solution at the same NaCl and NB concentration twice per day in order to maintain the freshness level of the feed solution.
Upon completion of the fouling test, the RO system was cleaned with:
Tap water adjusted to pH 2 with HNO3 for 1.5 hours
Tap water adjusted to pH 11 with NaOH for 1.5 hours
Flowing tap water for rinsing for 1.5 hours
Final rinsing with Milli-Q water at unadjusted pH
The fouled membranes were removed from the RO cells for membrane autopsy. In this analysis, fluorescence staining methods and confocal laser scanning microscope (CLSM) were used to detect the biofilm.
Biofilms were prepared for CLSM by staining with the LIVE/DEAD BacLight Bacterial Viability Kits (Molecular Probes, L7012). It consists of SYTO 9 green-fluorescent nucleic acid stain and the red-fluorescent nucleic acid stain, propidium iodide (PI). These stains possess different spectral characteristics and different ability to penetrate healthy bacterial cells. When used alone, the SYTO 9 stain generally labels all bacteria in a population — those with intact and damaged membranes. In contrast, propidium iodide penetrates only bacteria with damaged membranes, causing a reduction in the SYTO 9 stain fluorescence when both dyes are present. Thus, with an appropriate mixture of the SYTO 9 and propidium iodide stains, bacteria with intact cell membranes stain fluorescent green, whereas bacteria with damaged membranes stain fluorescent red.
Microscopic observation and image acquisition of biofilms were performed using a confocal laser scanning microscope (ZEISS, model LSM710), equipped with Argon laser at 488 nm and DPSS561-10 laser at 561 nm. Images were captured using confocal microscope bundled program ZEN 2009.
Results and discussions
The cross-flow velocity (CFV) in RO membrane operations is known to affect fouling rate. At higher CFV, the flow causes scouring effects which results in slower fouling (Koltuniewicz et al., 1995). On the other hand, experiments of RO modules without the presence of flux shows that a higher cross-flow velocity may increase biofouling due to more nutrients supply (Vrouwenvelder et al., 2009b).
In our study, the investigation was carried out by varying the cross-flow velocity (CFV) from
0.1, 0.17, to 0.34 m/s. The NaCl concentration used was constant at 2000 mg/L and the applied flux was constant at 35 LMH. TMP values were measured overtime and normalized to the initial TMP.
Figure 3 shows the normalized TMP profiles. Faster TMP rise was observed at lower CFV and both operation with and without spacer show similar profiles. The delay of TMP rise caused by spacer was quantified by measuring the time needed for the TMP to increase by 10 % (Table 1). The effect of spacer was higher at higher CFV where the percentage of the delay was 21.21 % and 42.87 % at 0.10 m/s and 0.17 m/s respectively. An interesting phenomenon was observed during the earlier TMP rise (0-3 days) where change in CFV gives little effect on TMP profiles. Similar phenomenon was observed for operation with and without spacer. A possible explanation for this phenomenon is that during this period bacterial attachment was dominant and therefore operation at constant flux gives similar initial TMP rise. Previous studies (Chong et al., 2008) have shown previously that membrane biofouling is a flux driven process where higher flux increases the TMP rise. However, their study did not include spacers and did not focus on initial TMP rise.
Table 1. The delay of biofouling rate caused by spacer at different CFV
The effect of different salt concentrations was also investigated. In this experiment the flux and CFV were fixed at 35 LMH and 0.17 m/s respectively. Figure 4 shows the normalized TMP profile of three different NaCl concentrations in the feed solution. When the feed channel spacer was absent it was very obvious that faster TMP rise was observed at higher salt concentration. This suggests that the effect of concentration polarization (CP) increases with the salt concentration and confirms the presence of the biofilm enhanced osmotic pressure (BEOP) effect (Herzberg and Elimelech, 2007; Chong et al., 2008). This phenomenon however, was less obvious when the spacer was present on the membrane. The spacer appears to provide flow eddies thus reducing the effect of CP and to be useful to prevent biofouling on the membrane which was indicated with slower TMP rise. The spacer gives bigger effect at higher salt concentration where the time to reach 10 % TMP rise was delayed by 30 % at 100 mg/L and 2000 mg/L NaCl, and 95.7 % at 4000 mg/L (Table 2).
4.2 Biofilm development in spacer-filled RO membrane channel The development of biofilm in spacer-filled channel was observed via microscopic and microscopic method. Macroscopic images are to show overall uniformity of biofilm distribution, while the microscopic images are able to show a more detailed biofilm patterns. All of the images in this study were taken from separate experiments as the samples were unable to be reused after analysis, however all the conditions for the experiments were maintained the same.
Figure 5 shows the macroscopic images of biofilm development. The biofilm sample on the membranes and spacers were stained with 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) dye. CTC stains bacteria with respiration activity and stained cells appear in red colour. Analysis was done after 0, 3, 6, and 10 days, the condition was 35 LMH flux, 0.17 m/s CFV, and 4000 mg/L NaCl concentration. Longer experiment duration gives thicker and denser biofilm, which can be seen from higher red colour intensity. The biofilms have also shown overall uniformity across the membrane area where similar patterns were observed among each spacer squares.
Figure 5. Macroscopic images of biofilm development on membranes and spacers. (A) 0-day, (B) 3-day, (C) 6-day, (D) 10-day. Biofilms stained with CTC dye and images taken with SONY NEX-5 digital camera.
Confocal laser scanning microscope (CLSM) provides a more detailed analysis of biofilm development (Figure 6). Based on the images, it appears that biofilm was initiated on the membrane; it later covered more areas and started to appear on the spacer. Areas behind the attached filaments of the spacer fiber seem to be suitable for the initial bacterial attachments rather than the centre of the spacer. Biofilm build-up observed on areas under the detached filaments was caused by higher shear due to accelerated CFV. Our experiments confirmed that biofouling in RO is a flux driven process. A lower TMP rise was observed at lower flux, which means slower biofouling rate. This is also supported with the biofilm coverage data where less coverage was observed at lower flux.
From the findings above, several conclusions can be drawn. The hydrodynamic condition of the flow is affecting the biofouling process. Cross flow velocity (CFV) is an important parameter and lower fouling can be achieved at higher CFV. Having feed channel spacers on the membrane is advantageous as it provides a more well-mixed flow, reduces concentration polarization and reduces TMP increase. Biofilm enhanced osmotic pressure (BEOP) was another phenomenon observed in this study. Due to the BEOP effect, a faster TMP rise was achieved at higher salinity. However, with the presence of the spacer the BEOP effect was reduced significantly.
From our microscopic analysis of biofilm shows that initial bacterial deposition and biofilm development was started on the membrane especially on areas behind the attached spacer filaments. Biofilm develops over time to cover more areas and starts to grow on the spacer at the later stages. Imposed flux also influences the biofilm development where lower biofouling is achieved at lower flux.
Baker, J. S. and Dudley, L. Y. (1998), “Biofouling in membrane systems – a review”, Desalination, Vol. 118, No. 1-3, pp. 81-90.
Chong, T. H., Wong, F. S. and Fane, A. G. (2008), “The effect of imposed flux on biofouling in reverse osmosis: Role of concentration polarisation and biofilm enhanced osmotic pressure phenomena”, Journal of Membrane Science, Vol. 325, No. 2, pp. 840-850.
Flemming, H. C. (1997), “Reverse osmosis membrane biofouling”, Experimental Thermal and Fluid Science, Vol. 14, No. 4, pp. 382-391.
Herzberg, M. and Elimelech, M. (2007), “Biofouling of reverse osmosis membranes: Role of biofilm-enhanced osmotic pressure”, Journal of Membrane Science, Vol. 295, No. 1-2, pp.
Koltuniewicz, A. B., Field, R. W. and Arnot, T. C. (1995), “Cross-flow and dead-end microfiltration of oily-water emulsion. Part I: Experimental study and analysis of flux decline”, Journal of Membrane Science, Vol. 102, No. 1-3, pp. 193-207.
Suwarno, S. R., Puspitasari, V. L., Chong, T. H., Fane, A. G., Chen, X., Rice, S. A., Mcdougald, D. and Cohen, Y. (2010) “The hydrodynamic effect on biofouling in reverse osmosis membrane processes”, IWA International Young Water Professionals Conference, Sydney,
Vrouwenvelder, J. S., Hinrichs, C., Van Der Meer, W. G., Van Loosdrecht, M. C. and Kruithof, J. C. (2009b), “Pressure drop increase by biofilm accumulation in spiral wound RO and NF membrane systems: role of substrate concentration, flow velocity, substrate load and flow direction”, Biofouling, Vol. 25, No. 6, pp. 543-555.
Wangnick (2005), 2004 Worldwide Desalting Plants Directory, Global Water Intelligence, Oxford, England.
Experimental Methods in Wastewater Treatment – M.C.M. van Loosdrecht, J. Keller, P.H. Nielsen, C.M. Lopez-Vazquez and D. Brdjanovic
Publication Date: Feb 2014 – ISBN – 9781780404745
TweetDesalination refers to processes that remove some amount of salt and other minerals from saline water. Salt water is desalinated to produce fresh water suitable for human consumption or irrigation. One potential byproduct of desalination is salt. Desalination is used on many seagoing ships and submarines. Most of the modern interest in desalination is focused […]
Desalination refers to processes that remove some amount of salt and other minerals from saline water.
Salt water is desalinated to produce fresh water suitable for human consumption or irrigation. One potential byproduct of desalination is salt. Desalination is used on many seagoing ships and submarines. Most of the modern interest in desalination is focused on developing cost-effective ways of providing fresh water for human use. Along with recycled wastewater, this is one of the few rainfall-independent water sources.
Large-scale desalination typically uses large amounts of energy and specialized, expensive infrastructure, making it more expensive than fresh water from conventional sources, such as rivers or groundwater.
Desalination is particularly relevant to countries such as Australia, which traditionally have relied on collecting rainfall behind dams to provide their drinking water supplies.
According to the International Desalination Association, in 2009, 14,451 desalination plants operated worldwide, producing 59.9e6 cubic meters (2.12×109 cu ft) per day, a year-on-year increase of 12.3%. It was 68 million m3 in 2010, and expected to hit 120 million m3 by 2020; some 40 million m3 is planned for the Middle East. The world’s largest desalination plant is the Jebel Ali Desalination Plant (Phase 2) in the United Arab Emirates.
Schematic of a multistage flash desalinator
A – steam in
B – seawater in
C – potable water out
D – waste out
E – steam out
F – heat exchange
G – condensation collection
H – brine heater
Plan of a typical reverse osmosis desalination plant
The traditional process used in these operations is vacuum distillation—essentially the boiling of water at less than atmospheric pressure and thus a much lower temperature than normal. This is because the boiling of a liquid occurs when the vapor pressure equals the ambient pressure and vapor pressure increases with temperature. Thus, because of the reduced temperature, energy is saved. Multistage flash distillation, a leading method, accounted for 85% of production worldwide in 2004.
The principal competing processes use membranes to desalinate, principally applying reverse osmosis technology. Membrane processes use semipermeable membranes and pressure to separate salts from water. Reverse osmosis plant membrane systems typically use less energy than thermal distillation, which has led to a reduction in overall desalination costs over the past decade. Desalination remains energy intensive, however, and future costs will continue to depend on the price of both energy and desalination technology.
Cogeneration is the process of using excess heat from power production to accomplish another task. For desalination, cogeneration is the production of potable water from seawater or brackish groundwater in an integrated, or “dual-purpose”, facility in which a power plant becomes the source of energy for desalination. Alternatively, the facility’s energy production may be dedicated to the production of potable water (a stand-alone facility), or excess energy may be produced and incorporated into the energy grid (a true cogeneration facility). Cogeneration takes various forms, and theoretically any form of energy production could be used. However, the majority of current and planned cogeneration desalination plants use either fossil fuels or nuclear power as their source of energy. Most plants are located in the Middle East or North Africa, which use their petroleum resources to offset limited water resources. The advantage of dual-purpose facilities is they can be more efficient in energy consumption, thus making desalination a more viable option for drinking water.
The Shevchenko BN350, a nuclear-heated desalination unit
In a December 26, 2007, opinion column in The Atlanta Journal-Constitution, Nolan Hertel, a professor of nuclear and radiological engineering at Georgia Tech, wrote, “… nuclear reactors can be used … to produce large amounts of potable water. The process is already in use in a number of places around the world, from India to Japan and Russia. Eight nuclear reactors coupled to desalination plants are operating in Japan alone … nuclear desalination plants could be a source of large amounts of potable water transported by pipelines hundreds of miles inland…”
Additionally, the current trend in dual-purpose facilities is hybrid configurations, in which the permeate from a reverse osmosis desalination component is mixed with distillate from thermal desalination. Basically, two or more desalination processes are combined along with power production. Such facilities have already been implemented in Saudi Arabia at Jeddah and Yanbu.
A typical aircraft carrier in the US military uses nuclear power to desalinate 400,000 US gallons (1,500,000 l; 330,000 imp gal) of water per day.
Factors that determine the costs for desalination include capacity and type of facility, location, feed water, labor, energy, financing, and concentrate disposal. Desalination stills now control pressure, temperature and brine concentrations to optimize efficiency. Nuclear-powered desalination might be economical on a large scale.
While noting costs are falling, and generally positive about the technology for affluent areas in proximity to oceans, a 2004 study argued, “Desalinated water may be a solution for some water-stress regions, but not for places that are poor, deep in the interior of a continent, or at high elevation. Unfortunately, that includes some of the places with biggest water problems.”, and, “Indeed, one needs to lift the water by 2,000 meters (6,600 ft), or transport it over more than 1,600 kilometers (990 mi) to get transport costs equal to the desalination costs. Thus, it may be more economical to transport fresh water from somewhere else than to desalinate it. In places far from the sea, like New Delhi, or in high places, like Mexico City, high transport costs would add to the high desalination costs. Desalinated water is also expensive in places that are both somewhat far from the sea and somewhat high, such as Riyadh and Harare. In many places, the dominant cost is desalination, not transport; the process would therefore be relatively less expensive in places like Beijing, Bangkok, Zaragoza, Phoenix, and, of course, coastal cities like Tripoli.” After being desalinated at Jubail, Saudi Arabia, water is pumped 200 miles (320 km) inland through a pipeline to the capital city of Riyadh. For coastal cities, desalination is increasingly viewed as an untapped and unlimited water source.
In Israel as of 2005, desalinating water costs US$ 0.53 per cubic meter. As of 2006, Singapore was desalinating water for US$ 0.49 per cubic meter. The city of Perth began operating a reverse osmosis seawater desalination plant in 2006, and the Western Australian government announced a second plant will be built to serve the city’s needs. A desalination plant is now operating in Australia’s largest city, Sydney, and the Wonthaggi desalination plant was under construction in Wonthaggi, Victoria.
The Perth desalination plant is powered partially by renewable energy from the Emu Downs Wind Farm. A wind farm at Bungendore in New South Wales was purpose-built to generate enough renewable energy to offset the Sydney plant’s energy use, mitigating concerns about harmful greenhouse gas emissions, a common argument used against seawater desalination.
In December 2007, the South Australian government announced it would build a seawater desalination plant for the city of Adelaide, Australia, located at Port Stanvac. The desalination plant was to be funded by raising water rates to achieve full cost recovery. An online, unscientific poll showed nearly 60% of votes cast were in favor of raising water rates to pay for desalination.
A January 17, 2008, article in the Wall Street Journal stated, “In November, Connecticut-based Poseidon Resources Corp. won a key regulatory approval to build the $300 million water-desalination plant in Carlsbad, north of San Diego. The facility would produce 50,000,000 US gallons (190,000,000 l; 42,000,000 imp gal) of drinking water per day, enough to supply about 100,000 homes … Improved technology has cut the cost of desalination in half in the past decade, making it more competitive … Poseidon plans to sell the water for about $950 per acre-foot [1,200 cubic metres (42,000 cu ft)]. That compares with an average [of] $700 an acre-foot [1200 m³] that local agencies now pay for water.” Each $1,000 per acre-foot works out to $3.06 for 1,000 gallons, or $.81 per cubic meter.
While this regulatory hurdle was met, Poseidon Resources is not able to break ground until the final approval of a mitigation project for the damage done to marine life through the intake pipe is received, as required by California law. Poseidon Resources has made progress in Carlsbad, despite an unsuccessful attempt to complete construction of Tampa Bay Desal, a desalination plant in Tampa Bay, FL, in 2001. The Board of Directors of Tampa Bay Water was forced to buy Tampa Bay Desal from Poseidon Resources in 2001 to prevent a third failure of the project. Tampa Bay Water faced five years of engineering problems and operation at 20% capacity to protect marine life, so stuck to reverse osmosis filters prior to fully using this facility in 2007.
In 2008, a San Leandro, California company (Energy Recovery Inc.) was desalinating water for $0.46 per cubic meter.
A Jordanian-born chemical engineering doctoral student at University of Ottawa, Mohammed Rasool Qtaisha, invented a new desalination technology that is alleged to produce between 600% and 700% more water output per square meter of membrane than current technology. General Electric is looking into similar technology, and the U.S. National Science Foundation funded the University of Michigan to study it, as well. Patent issues and details of the technology were unresolved as of 2008.
While desalinating 1,000 US gallons (3,800 l; 830 imp gal) of water can cost as much as $3, the same amount of bottled water costs $7,945.
In the United States, due to a recent court ruling under the Clean Water Act, ocean water intakes are no longer viable without reducing mortality of the life in the ocean, the plankton, fish eggs and fish larvae, by 90%. The alternatives include beach wells to eliminate this concern, but require more energy and higher costs, while limiting output.
All desalination processes produce large quantities of a concentrate, which may be increased in temperature, and contain residues of pretreatment and cleaning chemicals, their reaction byproducts, and heavy metals due to corrosion. Chemical pretreatment and cleaning are a necessity in most desalination plants, which typically includes the treatment against biofouling, scaling, foaming and corrosion in thermal plants, and against biofouling, suspended solids and scale deposits in membrane plants.
To limit the environmental impact of returning the brine to the ocean, it can be diluted with another stream of water entering the ocean, such as the outfall of a wastewater treatment or power plant. While seawater power plant cooling water outfalls are not as fresh as wastewater treatment plant outfalls, salinity is reduced. If the power plant is medium-to-large sized and the desalination plant is not enormous, the power plant’s cooling water flow is likely to be at least several times larger than that of the desalination plant. Another method to reduce the increase in salinity is to mix the brine via a diffuser in a mixing zone. For example, once the pipeline containing the brine reaches the sea floor, it can split into many branches, each releasing brine gradually through small holes along its length. Mixing can be combined with power plant or wastewater plant dilution.
Brine is denser than seawater due to higher solute concentration. The ocean bottom is most at risk because the brine sinks and remains there long enough to damage the ecosystem. Careful reintroduction can minimize this problem. For example, for the desalination plant and ocean outlet structures to be built in Sydney from late 2007, the water authority stated the ocean outlets would be placed in locations at the seabed that will maximize the dispersal of the concentrated seawater, such that it will be indistinguishable beyond between 50 and 75 meters (160 and 246 ft) from the outlets. Typical oceanographic conditions off the coast allow for rapid dilution of the concentrated byproduct, thereby minimizing harm to the environment.
The Kwinana Desalination Plant opened in Perth in 2007. Water there and at Queensland’s Gold Coast Desalination Plant and Sydney’s Kurnell Desalination Plant is withdrawn at only 0.1 meters per second (0.33 ft/s), which is slow enough to let fish escape. The plant provides nearly 140,000 cubic meters (4,900,000 cu ft) of clean water per day.
Alternatives without pollution
Some methods of desalination, particularly in combination with evaporation ponds and solar stills (solar desalination), do not discharge brine. They do not use chemicals in their processes nor the burning of fossil fuels. They do not work with membranes or other critical parts, such as components that include heavy metals, thus do not cause toxic waste (and high maintenance). A new approach that works like a solar still, but on the scale of industrial evaporation ponds is the Integrated Biotectural System. It can be considered “full desalination” because it converts the entire amount of saltwater intake into distilled water. One of the unique advantages of this type of solar-powered desalination is the feasibility for inland operation. Standard advantages also include no air pollution from desalination power plants and no temperature increase of endangered natural water bodies from power plant cooling-water discharge. Another important advantage is the production of sea salt for industrial and other uses. Currently, 50% of the world’s sea salt production still relies on fossil energy sources.
Alternatives to desalination
Increased water conservation and efficiency remain the most cost-effective priorities in areas of the world where there is a large potential to improve the efficiency of water use practices. Wastewater reclamation for irrigation and industrial use provides multiple benefits over desalination. Urban runoff and storm water capture also provide benefits in treating, restoring and recharging groundwater.
A proposed alternative to desalination in the American Southwest is the commercial importation of bulk water from water-rich areas either by very large crude carriers converted to water carriers, or via pipelines. The idea is politically unpopular in Canada, where governments imposed trade barriers to bulk water exports as a result of a claim filed in 1999 under Chapter 11 of the North American Free Trade Agreement (NAFTA) by Sun Belt Water Inc., a company established in 1990 in Santa Barbara, California, to address pressing local needs due to a severe drought in that area.
Experimental techniques and other developments
Many desalination techniques have been researched, with varying degrees of success.
One such process was commercialized by Modern Water PLC using forward osmosis, with a number of plants reported to be in operation.
The US government is working to develop practical solar desalination.
The Passarell process uses reduced atmospheric pressure rather than heat to drive evaporative desalination. The pure water vapor generated by distillation is then compressed and condensed using an advanced compressor. The compression process improves distillation efficiency by creating the reduced pressure in the evaporation chamber. The compressor centrifuges the pure water vapor after it is drawn through a demister (removing residual impurities) causing it to compress against tubes in the collection chamber. The compression of the vapor causes its temperature to increase. The heat generated is transferred to the input water falling in the tubes, causing the water in the tubes to vaporize. Water vapor condenses on the outside of the tubes as product water. By combining several physical processes, Passarell enables most of the system’s energy to be recycled through its subprocesses, namely evaporation, demisting, vapor compression, condensation, and water movement within the system.
Geothermal energy can drive desalination. In most locations, geothermal desalination beats using scarce groundwater or surface water, environmentally and economically.
Nanotube membranes may prove to be effective for water filtration and desalination processes that would require substantially less energy than reverse osmosis.
Biomimetic membranes are another approach.
On June 23, 2008, Siemens Water Technologies announced technology based on applying electric fields that purports to desalinate one cubic meter of water while using only 1.5 kWh of energy. If accurate, this process would consume only one-half the energy of other processes. Currently, Oasis Water, which developed the technology, still uses three times that much energy.
Freeze-thaw desalination uses freezing to remove fresh water from frozen seawater.
In 2009, Lux Research estimated the worldwide desalinated water supply will triple between 2008 and 2020.
Desalination through evaporation and condensation for crops
The Seawater Greenhouse uses natural evaporation and condensation processes inside a greenhouse powered by solar energy to grow crops in arid coastal land.
Low-temperature thermal desalination
Originally stemming from ocean thermal energy conversion research, low-temperature thermal desalination (LTTD) takes advantage of water boiling at low pressures, potentially even at ambient temperature. The system uses vacuum pumps to create a low-pressure, low-temperature environment in which water boils at a temperature gradient of 8–10 °C (46–50 °F) between two volumes of water. Cooling ocean water is supplied from depths of up to 600 meters (2,000 ft). This cold water is pumped through coils to condense the water vapor. The resulting condensate is purified water. LTTD may also take advantage of the temperature gradient available at power plants, where large quantities of warm wastewater are discharged from the plant, reducing the energy input needed to create a temperature gradient.
Experiments were conducted in the US and Japan to test the approach. In Japan, a spray-ﬂash evaporation system was tested by Saga University. In Hawaii, the National Energy Laboratory tested an open-cycle OTEC plant with fresh water and power production using a temperature difference of 20 C° between surface water and water at a depth of around 500 meters (1,600 ft). LTTD was studied by India’s National Institute of Ocean Technology (NIOT) from 2004. Their first LTTD plant opened in 2005 at Kavaratti in the Lakshadweep islands. The plant’s capacity is 100,000 liters (22,000 imp gal; 26,000 US gal)/day, at a capital cost of INR 50 million (€922,000). The plant uses deep water at a temperature of 7 to 15 °C (45 to 59 °F). In 2007, NIOT opened an experimental, floating LTTD plant off the coast of Chennai, with a capacity of 1,000,000 litres (220,000 imp gal; 260,000 US gal)/day. A smaller plant was established in 2009 at the North Chennai Thermal Power Station to prove the LTTD application where power plant cooling water is available.
In October 2009, Saltworks Technologies, a Canadian firm, announced a process that uses solar or other thermal heat to drive an ionic current that removes all sodium and chlorine ions from the water using ion-exchange membranes.
Shared under the Creative Commons Attribution-ShareAlike License, original text and illustrations found here: http://en.wikipedia.org/wiki/Desalination
TweetChlorine Residuals The presence of free chlorine in drinking water indicates that: 1) a sufficient amount of chlorine was added to the water to inactivate most of the bacteria and viruses that cause diarrheal disease; and, 2) the water is protected from recontamination during transport to the home, and during storage of water in the […]
The presence of free chlorine in drinking water indicates that: 1) a sufficient amount of chlorine was added to the water to inactivate most of the bacteria and viruses that cause diarrheal disease; and, 2) the water is protected from recontamination during transport to the home, and during storage of water in the household. Because the presence of free residual chlorine in drinking water indicates the likely absence of disease-causing organisms, it is used as one measure of the potability of drinking water.
When chlorine is added to water as a disinfectant, a series of reactions occurs. These reactions are graphically depicted later in this article. The first of these reactions occurs when organic materials and metals present in the water react with the chlorine and transform it into compounds that are unavailable for disinfection. The amount of chlorine used in these reactions is termed the chlorine demand of the water. Any remaining chlorine concentration after the chlorine demand is met is termed total chlorine. Total chlorine is further subdivided into: 1) the amount of chlorine that then reacts with nitrates present in the water and is transformed into compounds that are much less effective disinfectants than free chlorine (termed combined chlorine); and, 2) the free chlorine, which is the chlorine available to inactivate disease-causing organisms, and is thus a measure used to determine the potability of water.
For example, when chlorine is added to completely pure water the chlorine demand will be zero, and there will be no nitrates present, so no combined chlorine will be formed. Thus, the free chlorine concentration will be equal to the concentration of chlorine added. When chlorine is added to natural waters, especially water from surface sources such as rivers, organic material will exert a chlorine demand, and combined chlorine will be formed by reaction with nitrates. Thus, the free chlorine concentration will be less than the concentration of chlorine initially
Chlorine Addition Flow Chart
Testing Free Chlorine in Drinking Water
Testing free chlorine is recommended in the following circumstances:
• To conduct dosage testing in project areas
• To monitor and evaluate projects by testing stored drinking water in households
The goal of dosage testing is to determine how much sodium hypochlorite solution to add to water that will be used for drinking to maintain free chlorine residual in the water for the average time of storage of water in the household (typically 24 hours). This goal differs from the goal of infrastructure-based (piped) water treatment systems, whose aim is effective disinfection at the endpoints (i.e., water taps) of the system. The WHO recommends “a residual concentration of free chlorine of greater than or equal to 0.5 mg/litre after at least 30 minutes contact time at pH less than 8.0.” This definition is only appropriate for users who obtain water directly from a flowing tap. A free chlorine level of 0.5 mg/L can maintain the quality of water through a distribution network, but is not optimal to maintain the quality of the water when it is stored in the home in a bucket or jerry can for 24 hours.
1. At 1 hour after the addition of sodium hypochlorite solution to water there should be no more than 2.0 mg/L of free chlorine residual present (this ensures the water does not have an unpleasant taste or odor).
2. At 24 hours after the addition of sodium hypochlorite to water in containers that are used by families for water storage there should be a minimum of 0.2 mg/L of free chlorine residual present (this ensures microbiologically clean water).
This methodology is approved by the World Health Organization (WHO), and is graphically depicted below. The maximum allowable WHO value for free chlorine residual in drinking water is 5 mg/L. The minimum recommended WHO value for free chlorine residual in treated drinking water is 0.2 mg/L. CDC recommends not exceeding 2.0 mg/L due to taste concerns, and chlorine residual decays over time in stored water.
1. Free Chlorine as an Indicator of Sanitizing Strength
Chlorine, which kills bacteria by way of its power as an oxidizing agent, is the most popular germicide used in water treatment. Chlorine is not only used as a primary disinfectant, but also to establish a sufficient residual level of Free Available Chlorine (FAC) for ongoing disinfection.
FAC is the chlorine that remains after a certain amount is consumed by killing bacteria or reacting with other organic (ammonia, fecal matter) or inorganic (metals, dissolved CO2, Carbonates, etc) chemicals in solution. Measuring the amount of residual free chlorine in treated water is a well accepted method for determining its effectiveness in microbial control.
The Myron L Company FCE method for measuring residual disinfecting power is based on ORP, the specific chemical attribute of chlorine (and other oxidizing germicides) that kills bacteria and microbes.
2. FCE Free Chlorine Unit
The 6PIIFCE is the first handheld device to detect free chlorine directly, by measuring ORP. The ORP value is converted to a concentration reading (ppm) using a conversion table developed by Myron L Company through a series of experiments that precisely controlled chlorine levels and excluded interferants.
Other test methods typically rely on the user visually or digitally interpreting a color change resulting from an added reagent-dye. The reagent used radically alters the sample’s pH and converts the various chlorine species present into a single, easily measured species. This ignores the effect of changing pH on free chlorine effectiveness and disregards the fact that some chlorine species are better or worse sanitizers than others.
The Myron L Company 6PIIFCE avoids these pitfalls. The chemistry of the test sample is left unchanged from the source water. It accounts for the effect of pH on chlorine effectiveness by including pH in its calculation. For these reasons, the Ultrameter II’s FCE feature provides the best reading-to-reading picture of the rise and fall in sanitizing effectivity of free available chlorine.
The 6PIIFCE also avoids a common undesirable characteristic of other ORP-based methods by including a unique Predictive ORP value in its FCE calculation. This feature, based on a proprietary model for ORP sensor behavior, calculates a final stabilized ORP value in 1 to 2 minutes rather than the 10 to 15 minutes or more that is typically required for an ORP measurement.
Tweet Hard water is water that has high mineral content. Hard drinking water is generally not harmful to one’s health, but can pose serious problems in industrial settings, where water hardness is monitored to avoid costly breakdowns in boilers, cooling towers, and other equipment that handles water. In domestic settings, hard water is often indicated […]
Hard drinking water is generally not harmful to one’s health, but can pose serious problems in industrial settings, where water hardness is monitored to avoid costly breakdowns in boilers, cooling towers, and other equipment that handles water. In domestic settings, hard water is often indicated by a lack of suds formation when soap is agitated in water. Wherever water hardness is a concern, water softening is commonly used to reduce hard water’s adverse effects.
Sources of hardness
Water’s hardness is determined by the concentration of multivalent cations in the water. Multivalent cations are cations (positively charged metal complexes) with a charge greater than 1+. Usually, the cations have the charge of 2+. Common cations found in hard water include Ca2+ and Mg2+. These ions enter a water supply by leaching from minerals within an aquifer. Common calcium-containing minerals are calcite and gypsum. A common magnesium mineral is dolomite (which also contains calcium). Rainwater and distilled water are soft, because they also contain few ions.
The following equilibrium reaction describes the dissolving/formation of calcium carbonate scales:
CaCO3 + CO2 + H2O ⇋ Ca2+ + 2HCO3−
Calcium carbonate scales formed in water-heating systems are called limescale.
Calcium and magnesium ions can sometimes be removed by water softeners.
Temporary hardness is a type of water hardness caused by the presence of dissolved bicarbonate minerals (calcium bicarbonate and magnesium bicarbonate). When dissolved, these minerals yield calcium and magnesium cations (Ca2+, Mg2+) and carbonate and bicarbonate anions (CO32-, HCO3-). The presence of the metal cations makes the water hard. However, unlike the permanent hardness caused by sulfate and chloride compounds, this “temporary” hardness can be reduced either by boiling the water, or by the addition of lime (calcium hydroxide) through the softening process of lime softening. Boiling promotes the formation of carbonate from the bicarbonate and precipitates calcium carbonate out of solution, leaving water that is softer upon cooling.
Permanent hardness is hardness (mineral content) that cannot be removed by boiling. When this is the case, it is usually caused by the presence of calcium and magnesium sulfates and/or chlorides in the water, which become more soluble as the temperature increases. Despite the name, the hardness of the water can be easily removed using a water softener, or ion exchange column.
Effects of hard water
With hard water, soap solutions form a white precipitate (soap scum) instead of producing lather. This effect arises because the 2+ ions destroy the surfactant properties of the soap by forming a solid precipitate (the soap scum). A major component of such scum is calcium stearate, which arises from sodium stearate, the main component of soap:
2 C17H35COO- + Ca2+ → (C17H35COO)2Ca
Hardness can thus be defined as the soap-consuming capacity of a water sample, or the capacity of precipitation of soap as a characteristic property of water that prevents the lathering of soap. Synthetic detergents do not form such scums.
Hard water also forms deposits that clog plumbing. These deposits, called “scale”, are composed mainly of calcium carbonate (CaCO3), magnesium hydroxide (Mg(OH)2), and calcium sulfate (CaSO4). Calcium and magnesium carbonates tend to be deposited as off-white solids on the surfaces of pipes and the surfaces of heat exchangers. This precipitation (formation of an insoluble solid) is principally caused by thermal decomposition of bi-carbonate ions but also happens to some extent even in the absence of such ions. The resulting build-up of scale restricts the flow of water in pipes. In boilers, the deposits impair the flow of heat into water, reducing the heating efficiency and allowing the metal boiler components to overheat. In a pressurized system, this overheating can lead to failure of the boiler. The damage caused by calcium carbonate deposits varies depending on the crystalline form, for example, calcite or aragonite.
The presence of ions in an electrolyte, in this case, hard water, can also lead to galvanic corrosion, in which one metal will preferentially corrode when in contact with another type of metal, when both are in contact with an electrolyte. The softening of hard water by ion exchange does not increase its corrosivity per se. Similarly, where lead plumbing is in use, softened water does not substantially increase plumbo-solvency.
In swimming pools, hard water is manifested by a turbid, or cloudy (milky), appearance to the water. Calcium and magnesium hydroxides are both soluble in water. The solubility of the hydroxides of the alkaline-earth metals to which calcium and magnesium belong (group 2 of the periodic table) increases moving down the column. Aqueous solutions of these metal hydroxides absorb carbon dioxide from the air, forming the insoluble carbonates, giving rise to the turbidity. This often results from the alkalinity (the hydroxide concentration) being excesively high (pH > 7.6). Hence, a common solution to the problem is to, while maintaining the chlorine concentration at the proper level, raise the acidity (lower the pH) by the addition of hydrochloric acid, the optimum value being in the range of 7.2 to 7.6.
For the reasons discussed above, it is often desirable to soften hard water. Most detergents contain ingredients that counteract the effects of hard water on the surfactants. For this reason, water softening is often unnecessary. Where softening is practiced, it is often recommended to soften only the water sent to domestic hot water systems so as to prevent or delay inefficiencies and damage due to scale formation in water heaters. A common method for water softening involves the use of ion exchange resins, which replace ions like Ca2+ by twice the number of monocations such as sodium or potassium ions.
The World Health Organization says that “there does not appear to be any convincing evidence that water hardness causes adverse health effects in humans”.
Some studies have shown a weak inverse relationship between water hardness and cardiovascular disease in men, up to a level of 170 mg calcium carbonate per litre of water. The World Health Organization has reviewed the evidence and concluded the data were inadequate to allow for a recommendation for a level of hardness.
Recommendations have been made for the maximum and minimum levels of calcium (40–80 ppm) and magnesium (20–30 ppm) in drinking water, and a total hardness expressed as the sum of the calcium and magnesium concentrations of 2–4 mmol/L.
Other studies have shown weak correlations between cardiovascular health and water hardness.
Some studies correlate domestic hard water usage with increased eczema in children.
The Softened-Water Eczema Trial (SWET), a multicenter randomized controlled trial of ion-exchange softeners for treating childhood eczema, was undertaken in 2008. However, no meaningful difference in symptom relief was found between children with access to a home water softener and those without.
Hardness can be quantified by instrumental analysis. The total water hardness is the sum of the molar concentrations of Ca2+ and Mg2+, in mol/L or mmol/L units. Although water hardness usually measures only the total concentrations of calcium and magnesium (the two most prevalent divalent metal ions), iron, aluminium, and manganese can also be present at elevated levels in some locations. The presence of iron characteristically confers a brownish (rust-like) colour to the calcification, instead of white (the color of most of the other compounds).
Water hardness is often not expressed as a molar concentration, but rather in various units, such as degrees of general hardness (dGH), German degrees (°dH), parts per million (ppm, mg/L, or American degrees), grains per gallon (gpg), English degrees (°e, e, or °Clark), or French degrees (°f). The table below shows conversion factors between the various units.
The various alternative units represent an equivalent mass of calcium oxide (CaO) or calcium carbonate (CaCO3) that, when dissolved in a unit volume of pure water, would result in the same total molar concentration of Mg2+ and Ca2+. The different conversion factors arise from the fact that equivalent masses of calcium oxide and calcium carbonates differ, and that different mass and volume units are used. The units are as follows:
Parts per million (ppm) is usually defined as 1 mg/L CaCO3 (the definition used below). It is equivalent to mg/L without chemical compound specified, and to American degree.
Grains per Gallon (gpg) is defined as 1 grain (64.8 mg) of calcium carbonate per U.S. gallon (3.79 litres), or 17.118 ppm.
a mmol/L is equivalent to 100.09 mg/L CaCO3 or 40.08 mg/L Ca2+.
A degree of General Hardness (dGH or ‘German degree (°dH, deutsche Härte)’ is defined as 10 mg/L CaO or 17.848 ppm.
A Clark degree (°Clark) or English degrees (°e or e) is defined as one grain (64.8 mg) of CaCO3 per Imperial gallon (4.55 litres) of water, equivalent to 14.254 ppm.
A French degree (°F or f) is defined as 10 mg/L CaCO3, equivalent to 10 ppm. The lowercase f is often used to prevent confusion with degrees Fahrenheit.
Because it is the precise mixture of minerals dissolved in the water, together with the water’s pH and temperature, that determines the behavior of the hardness, a single-number scale does not adequately describe hardness.
Langelier Saturation Index (LSI)
The Langelier Saturation Index (sometimes Langelier Stability Index) is a calculated number used to predict the calcium carbonate stability of water. It indicates whether the water will precipitate, dissolve, or be in equilibrium with calcium carbonate. In 1936, Wilfred Langelier developed a method for predicting the pH at which water is saturated in calcium carbonate (called pHs). The LSI is expressed as the difference between the actual system pH and the saturation pH:
LSI = pH (measured) — pHs
For LSI > 0, water is super saturated and tends to precipitate a scale layer of CaCO3.
For LSI = 0, water is saturated (in equilibrium) with CaCO3. A scale layer of CaCO3 is neither precipitated nor dissolved.
For LSI < 0, water is under saturated and tends to dissolve solid CaCO3. If the actual pH of the water is below the calculated saturation pH, the LSI is negative and the water has a very limited scaling potential. If the actual pH exceeds pHs, the LSI is positive, and being supersaturated with CaCO3, the water has a tendency to form scale. At increasing positive index values, the scaling potential increases. In practice, water with an LSI between -0.5 and +0.5 will not display enhanced mineral dissolving or scale forming properties. Water with an LSI below -0.5 tends to exhibit noticeably increased dissolving abilities while water with an LSI above +0.5 tends to exhibit noticeably increased scale forming properties. It is also worth noting that the LSI is temperature sensitive. The LSI becomes more positive as the water temperature increases. This has particular implications in situations where well water is used. The temperature of the water when it first exits the well is often significantly lower than the temperature inside the building served by the well or at the laboratory where the LSI measurement is made. This increase in temperature can cause scaling, especially in cases such as hot water heaters. Conversely, systems that reduce water temperature will have less scaling. Hard water in the United States
More than 85% of American homes have hard water. The softest waters occur in parts of the New England, South Atlantic-Gulf, Pacific Northwest, and Hawaii regions. Moderately hard waters are common in many of the rivers of the Tennessee, Great Lakes, and Alaska regions. Hard and very hard waters are found in some of the streams in most of the regions throughout the country. The hardest waters (greater than 1,000 ppm) are in streams in Texas, New Mexico, Kansas, Arizona, and southern California.
Measuring Hardness and LSI
The Myron L Ultrameter III 9PTK measures water hardness and LSI, as well as 7 other water quality parameters.
Measures 9 Parameters: Conductivity, Resistivity, TDS, Alkalinity, Hardness, LSI, pH, ORP/Free Chlorine, Temperature
LSI Calculator for hypothetical water balance calculations
Wireless data transfer capability with bluDock option
Auto-ranging delivers increased resolution across diverse applications
Adjustable Temperature Compensation and Cond/TDS conversion ratios for user-defined solutions
Nonvolatile memory of up to 100 readings for stored data protection
Date & time stamp makes record-keeping easy
pH calibration prompts alert you when maintenance is required
Auto-off minimizes energy consumption
Low battery indicator
(Includes instrument with case and solutions)
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TweetSince the 1960s, Myron L products have led the industry in high quality, simple to operate conductivity and pH instrumentation for municipal, commercial and industrial water quality control, chemical concentration testing and process control. Today, Myron L meters are more convenient than ever to research and buy right here at MyronLMeters.com. Industrial Wastewater Treatment Industrial […]
Since the 1960s, Myron L products have led the industry in high quality, simple to operate conductivity and pH instrumentation for municipal, commercial and industrial water quality control, chemical concentration testing and process control. Today, Myron L meters are more convenient than ever to research and buy right here at MyronLMeters.com.
Industrial Wastewater Treatment
Industrial wastewater treatment covers the mechanisms and processes used to treat waters that have been contaminated in some way by human industrial or commercial activities prior to its release into the environment or its re-use.
Most industries produce some wet waste although recent trends in the developed world have been to minimize such production or recycle waste within the production process. However, many industries remain dependent on processes that produce wastewaters.
Sources of industrial wastewater
Beer is a fermented beverage with low alcohol content made from various types of grain. Barley predominates, but wheat, maize, and other grains can be used. The production steps include:
• Malt production and handling: grain delivery and cleaning; steeping of the grain in water to start germination; growth of rootlets and development of enzymes (which convert starch into maltose); kilning and polishing of the malt to remove rootlets; storage of the cleaned malt
• Wort production: grinding the malt to grist; mixing grist with water to produce a mash in the mash tun; heating of the mash to activate enzymes; separation of grist residues in the lauter tun to leave a liquid wort; boiling of the wort with hops; separation of the wort from
the trub/hot break (precipitated residues), with the liquid part of the trub being returned
to the lauter tub and the spent hops going to a collection vessel; and cooling of the wort
• Beer production: addition of yeast to cooled wort; fermentation; separation of spent yeast
by filtration, centrifugation or settling; bottling or kegging.
Water consumption for breweries generally ranges 4–8 cubic meter per cubic meter (m3/m3) of beer produced.
Breweries can achieve an effluent discharge of 3–5 m3/m3 of sold beer (exclusive of cooling waters). Untreated effluents typically contain sus-pended solids in the range 10–60 milligrams per liter (mg/l), biochemical oxygen demand (BOD) in the range 1,000–1,500 mg/l, chemical oxygen demand (COD) in the range 1,800–3,000 mg/l,
and nitrogen in the range 30–100 mg/l. Phosphorus can also be present at concentrations of the order of 10–30 mg/l. Effluents from individual process steps are variable. For example, bottle washing produces a large volume of effluent that, however, contains only a minor part of the total organics discharged from the brewery. Effluents from fermentation
and filtering are high in organics and BOD but low in volume, accounting for about 3% of total wastewater volume but 97% of BOD. Effluent pH averages about 7 for the combined effluent but can fluctuate from 3 to 12 depending on the use of acid and alkaline cleaning agents. Effluent temperatures average about 30°C.
The dairy industry involves processing raw milk into products such as consumer milk, butter, cheese, yogurt, condensed milk, dried milk (milk powder), and ice cream, using processes such as chilling, pasteurization, and homogenization. Typical by-products include buttermilk, whey, and their derivatives.
Dairy effluents contain dissolved sugars and proteins, fats, and possibly residues of additives. The key parameters are biochemical oxygen demand (BOD), with an average ranging from 0.8 to 2.5 kilograms per metric ton (kg/t) of milk in the untreated effluent; chemical oxygen demand (COD), which is normally about 1.5 times the BOD level; total suspended solids, at 100–1,000 milligrams per liter (mg/l); total dissolved solids: phosphorus (10–100 mg/l), and nitrogen (about 6% of the BOD level). Cream, butter, cheese, and whey production are major sources of BOD in wastewater. The waste load equivalents of specific milk constituents are: 1 kg of milk fat = 3 kg COD; 1 kg of lactose = 1.13 kg COD; and 1 kg protein = 1.36 kg COD. The wastewater may contain pathogens from contaminated materials or production processes. A dairy often generates odors and, in some cases, dust, which need to be controlled. Most of the solid wastes can be processed into other products and byproducts.
Pulp and Paper industry
The pulp and paper industry is one of worlds oldest and core industrial sector. The socio-economic importance of paper has its own value to the country’s development as it is directly related to the industrial and economic growth of the country. Paper manufacturing is a highly capital, energy and water intensive industry. It is also a highly polluting process and requires substantial investments in pollution control equipment.
The pulp and paper mill is a major industrial sector utilizing a huge amount of lignocellulosic materials and water during the manufacturing process, and releases chlorinated lignosulphonic acids, chlorinated resin acids, chlorinated phenols and chlorinated hydrocarbons in the effluent. About 500 different chlorinated organic compounds have been identified including chloroform, chlorate, resin acids, chlorinated hydrocarbons, phenols, catechols, guaiacols, furans, dioxins, syringols, vanillins, etc. These compounds are formed as a result of reaction between residual lignin from wood fibres and chlorine/chlorine compounds used for bleaching. Colored compounds and Adsorbable Organic Halogens (AOX) released from pulp and paper mills into the environment poses numerous problems. The wood pulping and production of the paper products generate a considerable amount of pollutants characterized by Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Suspended Solids (SS), toxicity, and colour when untreated or poorly treated effluents are discharged to receiving waters. The effluent is toxic to aquatic organisms and exhibits strong mutagenic effects and physiological impairment.
Iron and steel industry
The production of iron from its ores involves powerful reduction reactions in blast furnaces. Cooling waters are inevitably contaminated with products especially ammonia andcyanide. Production of coke from coal in coking plants also requires water cooling and the use of water in by-products separation. Contamination of waste streams includes gasification products such as benzene, naphthalene, anthracene, cyanide, ammonia, phenols, cresols together with a range of more complex organic compounds known collectively as polycyclic aromatic hydrocarbons (PAH).
The conversion of iron or steel into sheet, wire or rods requires hot and cold mechanical transformation stages frequently employing water as a lubricant and coolant. Contaminants include hydraulic oils, tallow and particulate solids. Final treatment of iron and steel products before onward sale into manufacturing includes pickling in strong mineral acid to remove rust and prepare the surface for tin or chromium plating or for other surface treatments such as galvanisation or painting. The two acids commonly used arehydrochloric acid and sulfuric acid. Wastewaters include acidic rinse waters together with waste acid. Although many plants operate acid recovery plants, (particularly those using Hydrochloric acid), where the mineral acid is boiled away from the iron salts, there remains a large volume of highly acid ferrous sulfate or ferrous chloride to be disposed of. Many steel industry wastewaters are contaminated by hydraulic oil also known as soluble oil.
The principal waste-waters associated with mines and quarries are slurries of rock particles in water. These arise from rainfall washing exposed surfaces and haul roads and also from rock washing and grading processes. Volumes of water can be very high, especially rainfall related arisings on large sites. Some specialized separation operations, such as coalwashing to separate coal from native rock using density gradients, can produce wastewater contaminated by fine particulate haematite and surfactants. Oils and hydraulic oils are also common contaminants. Wastewater from metal mines and ore recovery plants are inevitably contaminated by the minerals present in the native rock formations. Following crushing and extraction of the desirable materials, undesirable materials may become contaminated in the wastewater. For metal mines, this can include unwanted metals such aszinc and other materials such as arsenic. Extraction of high value metals such as gold and silver may generate slimes containing very fine particles in where physical removal of contaminants becomes particularly difficult.
Mines and quarries
The principal wastewater associated with mines and quarries are slurries of rock particles in water. These arise from rainfall washing exposed surfaces and haul roads and also from rock washing and grading processes. Volumes of water can be very high, especially rainfall related arisings on large sites. Some specialized separation operations, such as coal washing to separate coal from native rock using density gradients, can produce wastewater contaminated by fine particulate hematite and surfactants. Oils and hydraulic oils are also common contaminants. Wastewater from metal mines and ore recovery plants are inevitably contaminated by the minerals present in the native rock formations. Following crushing and extraction of the desirable materials, undesirable materials may become contaminated in the wastewater. For metal mines, this can include unwanted metals such as zinc and other materials such as arsenic. Extraction of high value metals such as gold and silver may generate slimes containing very fine particles in where physical removal of contaminants becomes particularly difficult.
Wastewater generated from agricultural and food operations has distinctive characteristics that set it apart from common municipal wastewater managed by public or private wastewater treatment plants throughout the world: it is biodegradable and nontoxic, but that has high concentrations of biochemical oxygen demand (BOD) and suspended solids(SS). The constituents of food and agriculture wastewater are often complex to predict due to the differences in BOD and pH in effluents from vegetable, fruit, and meat products and due to the seasonal nature of food processing and postharvesting.
Processing of food from raw materials requires large volumes of high grade water. Vegetable washing generates waters with high loads of particulate matter and some dissolved organics. It may also contain surfactants.
Animal slaughter and processing produces very strong organic waste from body fluids, such as blood, and gut contents. This wastewater is frequently contaminated by significant levels of antibiotics and growth hormones from the animals and by a variety of pesticides used to control external parasites. Insecticide residues in fleeces is a particular problem in treating waters generated in wool processing.
Processing food for sale produces wastes generated from cooking which are often rich in plant organic material and may also contain salt, flavourings, colouring material and acidsor alkali. Very significant quantities of oil or fats may also be present.
Complex organic chemicals industry
A range of industries manufacture or use complex organic chemicals. These include pesticides, pharmaceuticals, paints and dyes, petro-chemicals, detergents, plastics, paper pollution, etc. Waste waters can be contaminated by feed-stock materials, by-products, product material in soluble or particulate form, washing and cleaning agents, solvents and added value products such as plasticisers.
The waste production from the nuclear and radio-chemicals industry is dealt with as Radioactive waste.
Many industries have a need to treat water to obtain very high quality water for demanding purposes. Water treatment produces organic and mineral sludges from filtration and sedimentation. Ion exchange using natural or synthetic resins removes calcium, magnesium and carbonate ions from water, replacing them with hydrogen and hydroxyl ions. Regeneration of ion exchange columns with strong acids and alkalis produces a wastewater rich in hardness ions which are readily precipitated out, especially when in admixture with other wastewaters.
Treatment of industrial wastewater
The different types of contamination of wastewater require a variety of strategies to remove the contamination.
Most solids can be removed using simple sedimentation techniques with the solids recovered as slurry or sludge. Very fine solids and solids with densities close to the density of water pose special problems. In such case filtration or ultrafiltration may be required. Although, flocculation may be used, using alum salts or the addition of polyelectrolytes.
Oils and grease removal
Many oils can be recovered from open water surfaces by skimming devices. Considered a dependable and cheap way to remove oil, grease and other hydrocarbons from water, oil skimmers can sometimes achieve the desired level of water purity. At other times, skimming is also a cost-efficient method to remove most of the oil before using membrane filters and chemical processes. Skimmers will prevent filters from blinding prematurely and keep chemical costs down because there is less oil to process.
Because grease skimming involves higher viscosity hydrocarbons, skimmers must be equipped with heaters powerful enough to keep grease fluid for discharge. If floating grease forms into solid clumps or mats, a spray bar, aerator or mechanical apparatus can be used to facilitate removal.
However, hydraulic oils and the majority of oils that have degraded to any extent will also have a soluble or emulsified component that will require further treatment to eliminate. Dissolving or emulsifying oil using surfactants or solvents usually exacerbates the problem rather than solving it, producing wastewater that is more difficult to treat.
The wastewaters from large-scale industries such as oil refineries, petrochemical plants, chemical plants, and natural gas processing plants commonly contain gross amounts of oil and suspended solids. Those industries use a device known as an API oil-water separator which is designed to separate the oil and suspended solids from their wastewater effluents. The name is derived from the fact that such separators are designed according to standards published by the American Petroleum Institute (API).
The API separator is a gravity separation device designed by using Stokes Law to define the rise velocity of oil droplets based on their density and size. The design is based on thespecific gravity difference between the oil and the wastewater because that difference is much smaller than the specific gravity difference between the suspended solids and water. The suspended solids settles to the bottom of the separator as a sediment layer, the oil rises to top of the separator and the cleansed wastewater is the middle layer between the oil layer and the solids.
Typically, the oil layer is skimmed off and subsequently re-processed or disposed of, and the bottom sediment layer is removed by a chain and flight scraper (or similar device) and a sludge pump. The water layer is sent to further treatment consisting usually of an Electroflotation module for additional removal of any residual oil and then to some type of biological treatment unit for removal of undesirable dissolved chemical compounds.
A typical API oil-water separator used in many industries
Parallel plate separators are similar to API separators but they include tilted parallel plate assemblies (also known as parallel packs). The parallel plates provide more surface for suspended oil droplets to coalesce into larger globules. Such separators still depend upon the specific gravity between the suspended oil and the water. However, the parallel plates enhance the degree of oil-water separation. The result is that a parallel plate separator requires significantly less space than a conventional API separator to achieve the same degree of separation.
A typical parallel plate separator
Removal of biodegradable organics
Biodegradable organic material of plant or animal origin is usually possible to treat using extended conventional wastewater treatment processes such as activated sludge ortrickling filter. Problems can arise if the wastewater is excessively diluted with washing water or is highly concentrated such as neat blood or milk. The presence of cleaning agents, disinfectants, pesticides, or antibiotics can have detrimental impacts on treatment processes.
Activated sludge process
A generalized, schematic diagram of an activated sludge process.
Activated sludge is a biochemical process for treating sewage and industrial wastewater that uses air (or oxygen) and microorganisms to biologically oxidize organic pollutants, producing a waste sludge (or floc) containing the oxidized material. In general, an activated sludge process includes:
An aeration tank where air (or oxygen) is injected and thoroughly mixed into the wastewater.
A settling tank (usually referred to as a “clarifier” or “settler”) to allow the waste sludge to settle. Part of the waste sludge is recycled to the aeration tank and the remaining waste sludge is removed for further treatment and ultimate disposal.
Trickling filter process
A cross-section of the contact face of the bed media in a trickling filter
A trickling filter consists of a bed of rocks, gravel, slag, peat moss, or plastic media over which wastewater flows downward and contacts a layer (or film) of microbial slime covering the bed media. Aerobic conditions are maintained by forced air flowing through the bed or by natural convection of air. The process involves adsorption of organic compounds in the wastewater by the microbial slime layer, diffusion of air into the slime layer to provide the oxygen required for the biochemical oxidation of the organic compounds. The end products include carbon dioxide gas, water and other products of the oxidation. As the slime layer thickens, it becomes difficult for the air to penetrate the layer and an inner anaerobic layer is formed.
The components of a complete trickling filter system are: fundamental components:
- A bed of filter medium upon which a layer of microbial slime is promoted and developed.
- An enclosure or a container which houses the bed of filter medium.
- A system for distributing the flow of wastewater over the filter medium.
- A system for removing and disposing of any sludge from the treated effluent.
The treatment of sewage or other wastewater with trickling filters is among the oldest and most well characterized treatment technologies.
A trickling filter is also often called a trickle filter, trickling biofilter, biofilter, biological filter or biological trickling filter.
Treatment of other organics
Synthetic organic materials including solvents, paints, pharmaceuticals, pesticides, coking products and so forth can be very difficult to treat. Treatment methods are often specific to the material being treated. Methods include Advanced Oxidation Processing, distillation, adsorption, vitrification, incineration, chemical immobilization or landfill disposal. Some materials such as detergents may be capable of biological degradation and in such cases, a modified form of wastewater treatment can be used.
Treatment of acids and alkalis
Acids and alkalis can usually be neutralized under controlled conditions. Neutralisation frequently produces a precipitate that will require treatment as a solid residue that may also be toxic. In some cases, gasses may be evolved requiring treatment for the gas stream. Some other forms of treatment are usually required following neutralisation.
Waste streams rich in hardness ions as from de-ionisation processes can readily lose the hardness ions in a buildup of precipitated calcium and magnesium salts. This precipitation process can cause severe furring of pipes and can, in extreme cases, cause the blockage of disposal pipes. A 1 metre diameter industrial marine discharge pipe serving a major chemicals complex was blocked by such salts in the 1970s. Treatment is by concentration of de-ionisation waste waters and disposal to landfill or by careful pH management of the released wastewater.
Treatment of toxic materials
Toxic materials including many organic materials, metals (such as zinc, silver, cadmium, thallium, etc.) acids, alkalis, non-metallic elements (such as arsenic or selenium) are generally resistant to biological processes unless very dilute. Metals can often be precipitated out by changing the pH or by treatment with other chemicals. Many, however, are resistant to treatment or mitigation and may require concentration followed by landfilling or recycling. Dissolved organics can be incinerated within the wastewater by Advanced Oxidation Processes.
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TweetHow many of these wastewater treatment technologies are you familiar with? What is the most effective combination of processes? How do you measure results? Who’s doing the best wastewater treatment research? Is this the best way? Or can the processes below be recombined, rethought, and retooled into something better? Activated sludge systems Advanced oxidation process […]
How many of these wastewater treatment technologies are you familiar with? What is the most effective combination of processes?
How do you measure results? Who’s doing the best wastewater treatment research?
Is this the best way? Or can the processes below be recombined, rethought, and retooled into something better?
Activated sludge systems
Advanced oxidation process
Aerobic granular reactor
Aerobic treatment system
API oil-water separator
Bioconversion of biomass to mixed alcohol fuels
Coarse bubble diffusers
Dissolved air flotation
Expanded granular sludge bed digestion
Fine bubble diffusers
Flocculation & sedimentation
Lamella clarifier (Inclined Plate Clarifier) 
Microbial fuel cell
NERV (Natural Endogenous Respiration Vessel)
Parallel plate oil-water separator
Rotating biological contactor
Sedimentation (water treatment)
Sequencing batch reactor
Submerged aerated filter
Upflow anaerobic sludge blanket digestion
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Tweet“Thousands have lived without love, not one without water” W.H.Auden Using ultraviolet radiation to treat contaminated water started in Europe in the early 1900’s. In 1904 the first UV quartz lamp was created. Its original purpose was to treat vitamin D deficiencies but later became an integral part of most current UV water treatment systems. […]
“Thousands have lived without love, not one without water” W.H.Auden
Using ultraviolet radiation to treat contaminated water started in Europe in the early 1900’s. In 1904 the first UV quartz lamp was created. Its original purpose was to treat vitamin D deficiencies but later became an integral part of most current UV water treatment systems. These systems did not become available until 1981 and were not widely used until 1992. The most promising use of UV treatment is in developing countries where water borne illnesses are so prevalent. Several low cost and low maintenance systems have been created and are currently being used in villages in India and Africa providing safe water to some of the poorest communities. The biggest hurdle for the widespread use of these systems is that they need a power supply to operate. Each of these systems follows the same simple design: water flows into the housing unit around the UV low pressure mercury lamps – maximum water depth is around 3 inches to insure the UV radiation can saturate the water to a high enough level that the bacteria and viruses within are neutralized. The water must be filtered before entering the UV treatment system as turbidity and dissolved solids in the water cuts down on the UV penetration into the water column.
The Science of UV treatment
How is UV radiation so effective at neutralizing bacteria and other micro-organisms? UV radiation is in the light spectrum below visible light and above x-rays. It has a wave length between 40-400nm. UVC 220-290nm is the portion of the UV spectrum used for anti bacterial purposes and has the ability to travel it the bodies of small organisms such as bacteria, viruses, yeasts and molds. The UV radiation attacks the DNA chain of these organisms causing them to loose their ability to reproduce effectively killing them. One down side to UV water treatment is that the deceased organisms will remain in the water without additional filtering to remove them.
Aftim Acra & Solar Water Disinfection
Aftim Acra is an active researcher and former professor of environmental engineering at the American University in Beirut. Acra and colleagues began research of solar water disinfection in 1979 and showed that the sun’s heat and radiation is capable of killing pathogens. The sun supplies infrared radiation, which heats the water and can kill some bacteria, as well as ultraviolet radiation, which scrambles the DNA of the bacteria to disable their reproduction functions. Depending on the temperature and clearness of the sky, solar disinfection of water in a plastic bottle can take as little as six hours of direct sunlight. SODIS (solar water disinfection) is a strategy of disinfecting water promoted by the Swiss Federal Institute of Aquatic Sciences and Technology. The SODIS organization works to give people the opportunity and means to have clean water. They work primary in South America, Asia, and Africa where there are high concentrations of people living without adequate water and water systems. The disinfection method they advocate involves filling a transparent container with contaminated water.
One problem in this method is its current reliance on plastic bottles. When the plastic these bottles are made from (Polyethylene terephthalate) react with the heat & UV radiation from the sun, chemicals in the plastic can be absorbed into the water. Another problem with the use of plastic bottles is the threads in the cap and spout of the bottle. This is one spot on the bottle that cannot be disinfected by the sun because the cap is covering it! So if the bottle is used to scoop up water from a dirty source, and then disinfected with the SODIS method, the water will only be recontaminated by the threads of the bottle once poured out. It is important to keep in mind of any possible points of recontamination (i.e. dirty hands, dirty containers).
Below is a list of some of the bacteria,viruses, molds etc. that UV treatment can remove from water and the ultraviolet dosage required to destroy greater than 99.9% of micro-organisms (measured in microwatt seconds per centimeter squared).
Bacillus megaterium (vegatative)
Bacillus subtills (vegatative)
Legionella pneumophilla (legionnaires disease)
Leptospira intrrogans (Infectious Jaundice)
Pseudomonas seruginosa (laboratory strain)
Pseudomonas aeruginosa (environmental strain)
Salmonella paratyphi (enteric fever)
Salmonella typhosa (typhoid fever)
Shigella dysenterai (dysentery)
Shigella Flexneri (dysentery)
Common yeast cake
|MOLD SPORES||microwatt sec/cm2|
|Penicillum digitatum (olive)
Penicillum expensum (olive)
PeniciHum roqueforti (green)
|Chlorella vulgaris (algae)||22000|
|Bacteriophage (E. coli)
UV Time Line
1900- UV radiation was used in some European countries to treat contaminated water.
1904- Heraeus, a medical company then, developed first UV quartz lamp in order to treat vitamin D deficiencies. That lamp developed into the tanning beds of today and into UV water treatment as well.
1976-UV water treatment was used in disinfection of aquatic systems in zoos and aquariums and in pools.It was also used in to disinfect potable and non potable water in ships.
1979- Sensors developed to monitor dose of UV to ensure a sufficient amount for disinfection. Amalgam lamps developed; which use mercury bound with bismuth and indium2, instead of just liquid mercury.
1981- Wide acceptance of UV treatment for drinking water.
1992- UV disinfection in wastewater markets open up.
1997- Aquafine Corp., a leading designer and manufacturer of high quality industrial ultraviolet water treatment systems, has nearly tripled its growth over the past four years. International business accounts for 60 percent of that growth. Aquafine now designs, manufactures and installs state-of-the-art ultraviolet water treatment systems.
2000-American Water Works Association program that investigated effectiveness of UV systems on cryptosporidium. An outbreak in Milwaukee, Wisconsin occurred in the early 1990’s Chlorination alone did not offer sufficient protection against cryptosporidium, however, UV treatment does. Sales of UV drinking water disinfection systems in the USA increased.
2001-Combination systems are being developed, a mixture of chlorination, UV, membrane filtration, reverse osmosis and ozone oxidation.
2005- The current market for UV purification systems is 30% of the total market for drinking water treatment technologies; this number is expected to rise dramatically over the next few years due to several new strict standards the U.S. Environmental Protection Agency will finalize in 2006.
2006- New EPA regulations will require drinking water to be protected against cryptosporidium and other pathogens (which chlorine can’t do effectively) and to reduce disinfection by products commonly associated with chlorine and ozone treatments.
2009- For more than 60 years, UV light has been used effectively for disinfection and purification in water treatment plants. UV light technology also is used widely in hospitals, laboratories, food and drug facilities, and in a number of consumer products.
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Tweet A Book On Desalination Plant Concentrate Management by Nikolay Voutchkov, PE, BCEE of Water Globe Consulting and one of Myron L Meters valued customers This book provides an overview of the alternatives for management of concentrate generated by brackish water and seawater desalination plants, as well as site specific […]
A Book On Desalination Plant Concentrate Management by Nikolay Voutchkov, PE, BCEE of Water Globe Consulting and one of Myron L Meters valued customers
This book provides an overview of the alternatives for management of concentrate generated by brackish water and seawater desalination plants, as well as site specific factors involved in the selection of the most viable alternative for a given project, and the environmental permitting requirements and studies associated with their implementation. The book focuses on widely used alternatives for disposal of concentrate, including discharge to surface water bodies; disposal to the wastewater collection system; deep well injection; land application; evaporation; and zero liquid discharge. Direct discharge through new outfall; discharge through existing wastewater treatment plant outfall; and co-disposal with the cooling water of existing coastal power plant are thoroughly described and design guidance for the use of these concentrate disposal alternatives is presented with engineers and practitioners in the field of desalination in mind. Key advantages, disadvantages, environmental impact issues and possible solutions are presented for each discharge alternative. Easy-to-use graphs depicting construction costs as a function of concentrate flowrate are provided for all key concentrate management alternatives.
Mr. Voutchkov is a registered professional engineer and a board certified environmental engineer (BCEE) by the American Academy of Environmental Engineers. He has over 25 years of experience in planning, environmental review, permitting and implementation of large seawater desalination, water treatment and water reclamation projects in the US and abroad. Mr. Voutchkov has extensive expertise with all phases of seawater desalination project delivery: from conceptual scoping, pilot testing and feasibility analysis; to front-end and detailed project design; environmental review and permitting; contractor procurement; project construction and operations oversight/asset management. Mr. Voutchkov is President of Water Globe Consulting a private company specialized in providing expert advisory services in the field of seawater desalination and reuse. For over 11 years prior to establishing his project advisory firm, Mr. Voutchkov was a Chief Technology Officer and Corporate Technical Director for Poseidon Resources, a private company involved in the development of the largest seawater desalination projects in the USA. In recognition of his outstanding efforts and contribution to the field of seawater desalination, Mr. Voutchkov has received a number of prestigious awards from the International Desalination Association, the International Water Association and the American Academy of Environmental Engineers. He is one of the principal authors of the American Water Works Association s Manual of Water Supply Practices on Reverse Osmosis and Nanofiltration and of the World Health Organization s Guidance for the Health and Environmental Aspects Applicable to Desalination. Mr. Voutchkov has published over 40 technical articles in the field of water and wastewater treatment and reuse, and is co-author of several books and manuals of practice on membrane treatment and desalination. He wrote a book on “Seawater Pretreatment”, which was published by Water Treatment Academy in 2010.
Desalination Plant Concentrate Management
By Nikolay Voutchkov, PE, BCEE
ISBN: 978-974-496-357-4, 181 pages, Hardcover, Published by Technobiz Communications
Ch. 1. Introduction to Concentrate Management
Ch. 2. Desalination Plant Discharge Characterization
2.1. Desalination Plant Waste Streams
2.3. Spent Pretreatment Backwash Water
2.4. Chemical Cleaning Residuals
Ch. 3. Surface Water Discharge of Concentrate
3.1. New Surface Water Discharge
3.2. Potential Environmental Impacts
3.3. Concentrate Treatment Prior to Surface Water Discharge
3.4. Design Guidelines for Surface Water Discharges
3.5. Costs for New Surface Water Discharge
3.6. Case Studies of New Surface Water Discharges
3.7. Co-Disposal with Wastewater Effluent
3.8. Co-Disposal with Power Plant Cooling Water
Ch. 4. Discharge to Sanitary Sewer
4.2. Potential Environmental Impacts
4.3. Effect on Sanitary Sewer Operations
4.4. Effect on Wastewater Treatment Operations
4.5. Effect on Water Reuse
4.6. Design and Configuration Guidelines
4.7. Costs for Sanitary Sewer Discharge
Ch. 5. Deep Well Injection
5.2. Potential Environmental Impacts
5.3. Criteria and Methods for Feasibility Assessment
5.4. Design and Configuration Guidelines
5.5. Injection Well Costs
Ch. 6. Land Application
6.2. Potential Environmental Impacts
6.3. Criteria and Methods for Feasibility Assessment
6.4. Design and Configuration Guidelines
6.5. Land Application Costs
Ch. 7. Evaporation Ponds
7.2. Potential Environmental Impacts
7.3. Criteria and Methods for Feasibility Assessment
7.4. Design and Configuration Guidelines
7.5. Evaporation Pond Costs
Ch. 8. Zero Liquid Discharge Concentrate Disposal Systems
8.2. Potential Environmental Impacts
8.3. Criteria and Methods for Feasibility Assessment
8.4. Design and Configuration Guidelines
8.5. Zero Liquid Discharge Costs
Ch. 9. Beneficial Use of Concentrate
9.1. Technology Overview
9.2. Feasibility of Beneficial Concentrate Use
Ch. 10. Regional Concentrate Management
10.1. Types of Regional Concentrate Management Systems
10.2. Use of Brackish Water Concentrate in SWRO Plants
Ch. 11. Non-Concentrate Residuals Management
11.1. Spent Pretreatment Backwash Water
11.2. Chemical Cleaning Residuals
Ch. 12. Comparison of Concentrate Management Alternatives
12.1. Selection of Concentrate Management Approach
12.3. Environmental Impacts
12.4. Regulatory Acceptance
12.5. Ease of Implementation
12.6. Site Footprint
12.7. Reliability and Operational Constraints
12.8. Energy Use
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