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
TweetTo help brighten your New Year, I have compiled a list of the top 10 New Year’s resolutions for business development – things you can do to dramatically help yourself, your brands and your company. 1. Experiment with nontraditional media Media isn’t about to stop proliferating or fragmenting. Marketers need to put a plan in […]
To help brighten your New Year, I have compiled a list of the top 10 New Year’s resolutions for business development – things you can do to dramatically help yourself, your brands and your company.
1. Experiment with nontraditional media
Media isn’t about to stop proliferating or fragmenting. Marketers need to put a plan in place to determine the nature, extent and return on an investment of something nontraditional.
2. Stop hating the sales people
Start treating the sales folks as marketing’s clients. Start mining your marketing database and giving information back to them. Show them how the information will help make them more money.
3. Lose your fear of numbers
Decide what you want to measure before you launch a campaign. It’s infinitely easier to explain your value to the boss with hardcore data, rather than offering nothing but your good name to back up major marketing decisions.
4. Use your relationships
Word-of-mouth is your best salesman – harness it with a robust referral program. When purchasers and business owners talk, they talk about business. Make the next happy hour discussion about your company, your products, and your referral program.
Got an easy way to help build your customers’ business? Share it! MyronLMeters.com has a stockless reseller program that’s easy, effective, and risk-free. Believe me, we tell our customers.
5. Stop promoting your brands to death and start building them
Spend money on real marketing communications – rather than just promotions – to tell folks what your brand stands for. Give them good reasons to buy your products or services that have nothing to do with a special offer or freebie. Are your products as durable as Myron L meters? Tell people!
6. Don’t specialize in only Partial Customer Satisfaction (PCS)
The University of Michigan‘s American Customer Satisfaction Index shows that the average cross-industry customer satisfaction score has fallen below 75% — basically a C grade. It goes without saying there is tremendous room for improvement here.
7. Walk a mile in your customers’ shoes
Get to know what makes your customers tick and what problems they have, and let insights about them drive your decisions.
8. Account-based marketing is always a sure thing
If you can’t get to anything else, make the time to hug your best customers. The fastest way to increase revenue is through customers who already know and love your brand.
9. Stop ignoring social media
It’s not going away soon, and there are some tangible, measurable results to be gained by using new marketing channels such as blogs, podcasts, RSS and video.
10. Monitor your online reputation
Today companies must closely watch their online reputation. Think about how you can put a system in place to monitor and react in case of a reputation crisis in the blogosphere.
All of us at Myron L Meters would like to take a moment to thank you for your business, and to wish you the best for 2013. Our business nearly doubled in 2012 and we have you to thank. We have great things in store for the new year – new products, new partners, expanded international shipping, and more. Let us know how we can be a better part of your growing business.
Material from Marketing Darwinism by Paul Dunay is licensed under a Creative Commons Attribution 3.0 United States License. Original found here: http://pauldunay.com/top-10-cmo-new-years-resolutions/
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)
Watch the video here:
Material from Wikipedia shared under the Creative Commons Attribution-ShareAlike License
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.
Shared via Creative Commons Attribution ShareAlike license. Original information found here: http://www.appropedia.org/UV_water_treatment
Tweet If you’re like Veolia, you have locations in 69 countries. Nalco operates in 130 countries. Why should they have to ship Ultrameters to their employees? They shouldn’t – it’s so fast, cheap, and easy to use Myron L Meters worldwide shipping. It’s easy – just click the Secure International […]
If you’re like Veolia, you have locations in 69 countries. Nalco operates in 130 countries. Why should they have to ship Ultrameters to their employees? They shouldn’t – it’s so fast, cheap, and easy to use Myron L Meters worldwide shipping. It’s easy – just click the Secure International Checkout button when you check out and follow the instructions. You’ll be surprised by our low rates.
How much does it cost to ship an Ultrameter II 6P to…
Rio de Janeiro?
With the 10% discount you receive at MyronLMeters.com, you can ship an Ultrameter II 6P to China for less than most American companies pay for it. So…now what’s stopping you?
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TweetEnvironmental Applications Keeping the water in our lakes, rivers, and streams clean requires monitoring of water quality at many points as it gradually makes its way from its source to our oceans. Over the years ever-increasing environmental concerns and regulations have heightened the need for increased diligence and tighter restrictions on wastewater quality. Control of […]
Keeping the water in our lakes, rivers, and streams clean requires monitoring of water quality at many points as it gradually makes its way from its source to our oceans. Over the years ever-increasing environmental concerns and regulations have heightened the need for increased diligence and tighter restrictions on wastewater quality. Control of water pollution was once concerned mainly with treating wastewater before it was discharged from a manufacturing facility into the nation’s waterways. Today, in many cases, there are restrictions on wastewater that is discharged to city sewer systems or to other publicly owned treatment facilities. Many jurisdictions even restrict or regulate the runoff of storm water — affecting not only industrial and commercial land, but also residential properties as well.
In its simplest form, water pollution management requires impoundment of storm water runoff for a specified period of time before being discharged. Normally, a few simple tests such as pH and suspended solids must be checked to verify compliance before release. If water is used in any way prior to discharge, then the monitoring requirements can expand significantly. For example, if the water is used for once-through cooling, testing may include temperature, pH, total dissolved solids (TDS), chemical oxygen demand (COD), and biochemical oxygen demand (BOD), to name a few.
Once water is used in a process, some form of treatment is often required before it can be discharged to a public waterway. If wastewater is discharged to a city sewer or publicly owned facility, and treatment is required, the quality is often measured and the cost is based not only on the quantity discharged, but also the amount of treatment required. As a minimum requirement suspended solids must be removed. Filtering or using clarifiers often accomplishes such removal. Monitoring consists of measuring total suspended solids (TSS) or turbidity.
If inorganic materials have been introduced into the water, their concentration must be reduced to an acceptable level. Inorganics, such as heavy metals, typically are removed by raising the pH to form insoluble metal oxides or metal hydroxides. The precipitated contaminants are filtered or settled out. Afterward, the pH must be adjusted back into a “normal” range, which often requires continuous monitoring of pH.
Organic materials by far require the most extensive treatment. Many different methods have been devised to convert soluble organic compounds into insoluble inorganic matter. Most of these involve some form of biological oxidation treatment. Bacteria are used to metabolize the organic materials into carbon dioxide and solids, which can be easily removed. To insure that these processes work smoothly and efficiently requires regular monitoring of the health of the biological organisms. The level of food (organic material), nutrients (nitrogen and phosphorous), dissolved oxygen, and pH are some of the parameters that must be controlled. After bio-oxidation the wastewater is filtered or clarified. Often the final effluent is treated with an oxidizing compound such as chlorine to kill any remaining bacterial agents, but any excess oxidant normally must be removed prior to discharge. Oxidation Reduction Potential (ORP)/Redox is ideal for monitoring the level of oxidants before and after removal. The final effluent stream must be monitored to make sure it meets all regulatory requirements.
The monitoring of wastewater pollution does not end there. Scientists are continuously testing water in streams, ground water, lakes, lagoons, and other bodies of water to determine if and what effects any remaining contamination is having on the receiving waters and its associated aquatic life. Measurements may include pH, conductivity, TDS, temperature, dissolved oxygen, TSS and organic levels (COD and BOD).
Environmental testing is not limited to monitoring of wastewater systems. Control of air emissions often includes gas-cleaning systems that involve the use of water. Wet scrubbers and wet electrostatic precipitators are included in this group. A flue gas desulfurization (FGD) system is one type of wet scrubber that uses slurry of lime, limestone, or other caustic material to react with sulfur compounds in the flue gas. The key to reliable operation of these units is proper monitoring of solids levels and pH. After use, the water in these systems must be treated or added to other wastewater from the plant, where it is treated by one of the methods previously discussed.
With proper monitoring, systems that maintain cleaner air and water can be operated efficiently and effectively. Such operation will go a long way toward maintaining a cleaner environment for future generations.
Myron L Meters offers a full line of handheld instruments and in-line monitor/controllers that can be used to measure or monitor many of the parameters previously mentioned. The following table lists some of the model numbers for measuring, monitoring, or controlling pH, conductivity, TDS and ORP. For additional information, please refer to our data sheets or Ask An Expert at MyronLMeters.com.
Note: When using a monitor/controller to measure pH in streams that contain heavy metals, sulfides, or other materials that react with silver, Myron L Meters recommends using a double junction pH sensor with a potassium nitrate (KNO3) reference gel to avoid fouling the silver electrode. See our 720II Sensor Selection Guide for pH and ORP Monitor/controllers for more information.
Ultrameter II 6P
Multi-Parameter: Conductivity, TDS, Resistivity, pH, ORP, Temperature, Free Chlorine (FCE)
+/-1% Accuracy of Reading
Memory Storage: Save up to 100 samples w/ Date & Time stamp
Wireless Download Module Optional
TweetA TDS Meter indicates the Total Dissolved Solids (TDS) of a solution (the concentration of dissolved solids in it). Since dissolved ionized solids such as salts and minerals increase the conductivity of a solution, a TDS meter measures the conductivity of the solution and estimates the TDS from that. Dissolved organic solids such as sugar […]
A TDS Meter indicates the Total Dissolved Solids (TDS) of a solution (the concentration of dissolved solids in it). Since dissolved ionized solids such as salts and minerals increase the conductivity of a solution, a TDS meter measures the conductivity of the solution and estimates the TDS from that.
Dissolved organic solids such as sugar and colloids don’t affect the conductivity of a solution much so a TDS meter does not include them in its reading.
Units of TDS
A TDS meter usually displays TDS in parts per million (ppm). For example, a TDS reading of 1 ppm would indicate there is 1 milligram of dissolved solids in each kilogram of water.
The two chief methods of measuring total dissolved solids are gravimetry and conductivity. Gravimetric methods are the most accurate and involve evaporating the liquid solvent and measuring the mass of residues left. This method is generally the best but time-consuming. If inorganic salts comprise the majority of TDS, gravimetric methods are recommended.
Electrical conductivity of water is directly related to the concentration of dissolved ionized solids in the water. Ions from the dissolved solids in water create the water’s ability to conduct an electrical current, which can be measured using a conventional conductivity meter or TDS meter. When correlated with laboratory TDS measurements, conductivity provides an approximate value for the TDS concentration.
Total Dissolved Solids (TDS) is a measure of the combined content of all inorganic and organic substances contained in a liquid in: molecular, ionized or micro-granular (colloidal sol) suspended form. The operational definition is that the solids must be small enough to survive filtration through a two micrometer sieve. Total dissolved solids are normally discussed only for freshwater systems, as salinity comprises some of the ions constituting the definition of TDS. The principal application of TDS is in the study of water quality for streams, rivers and lakes, although TDS is not generally considered a primary pollutant (e.g. it is not deemed to be associated with health effects) it is used as an indication of aesthetic characteristics of drinking water and as an aggregate indicator of the presence of a broad array of chemical contaminants.
Primary sources for TDS in receiving waters are agricultural and residential runoff, leaching of soil contamination and point source water pollution discharge from industrial or sewage treatment plants. The most common chemical constituents are calcium, phosphates, nitrates, sodium, potassium and chloride, which are found in nutrient runoff, storm water runoff and runoff from snowy climates where road de-icing salts are applied. The chemicals may be cations, anions, molecules or agglomerations on the order of one thousand or fewer molecules, so long as a soluble micro-granule is formed. More exotic and harmful elements of TDS are pesticides arising from surface runoff. Certain naturally occurring total dissolved solids arise from the weathering and dissolution of rocks and soils. The United States has established a secondary water quality standard of 500 mg/l to provide for palatability of drinking water.
TDS Measurement Applications
High TDS levels indicate hard water, which can cause scale buildup in pipes, valves, and filters, reducing performance and adding to system maintenance costs. These effects can be seen in aquariums, spas, swimming pools, and reverse osmosis water treatment systems. Typically, in these applications, total dissolved solids are tested frequently, and filtration membranes are checked in order to prevent adverse effects.
In the case of hydroponics and aquaculture, TDS is often monitored in order to create a water quality environment favorable for organism productivity. For freshwater oysters, trouts, and other high value seafood, highest productivity and economic returns are achieved by mimicking the TDS and pH levels of each species’ native environment. For hydroponic uses, TDS is considered one of the best indices of nutrient availability for the aquatic plants being grown.
Because the threshold of acceptable aesthetic criteria for human drinking water is 500 mg/l, there is no general concern for odor, taste, and color at a level much lower than is required for harm. A number of studies have been conducted and indicate various species’ reactions range from intolerance to outright toxicity due to elevated TDS. The numerical results must be interpreted cautiously, as true toxicity outcomes will relate to specific chemical constituents. Nevertheless, some numerical information is a useful guide to the nature of risks in exposing aquatic organisms or terrestrial animals to high TDS levels. Most aquatic ecosystems involving mixed fish fauna can tolerate TDS levels of 1000 mg/l.
Boilers & cooling towers, Deionization, Reverse osmosis, Chemical concentrations, Printing fountain solutions, Swimming pools & spas, Water pollution control, Wastewater & more…
Myron L Meters Top-selling TDS Meters
ULTRAPEN PT1 Conductivity – TDS – Salinity Pen
Accuracy of +/-1% of READING (+/-.2% at Calibration Point)
Reliable Repeatable Results
Solution modes: KCl, NaCl and 442
Automatic Temperature Compensation
Durable, Fully Potted Circuitry
EP-10: 0-10, 100, 1000, 10,000 micromhos/microsiemens
Instant and accurate TDS tests
Electronic Internal Standard for easy field calibration
Fast Auto Temperature Compensation
Rugged design for years of trouble-free testing
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Multi-Parameter: Conductivity, TDS, Resistivity, Temperature
+/-1% Accuracy of Reading
Memory Storage: Save up to 100 samples w/ Date & Time stamp
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