Sustainable Drinking Water Treatment For Small Communities Using Multistage Slow Sand Filtration Electronic Resource
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Sustainable Drinking Water Treatment For Small Communities Using Multistage Slow Sand Filtration Electronic Resource
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Author : Cleary, Shawn A
language : en
Publisher: University of Waterloo
Release Date : 2005
Sustainable Drinking Water Treatment For Small Communities Using Multistage Slow Sand Filtration Electronic Resource written by Cleary, Shawn A and has been published by University of Waterloo this book supported file pdf, txt, epub, kindle and other format this book has been release on 2005 with categories.
Slow sand filtration is a proven and sustainable technology for drinking water treatment in small communities. The process, however, is sensitive to lower water temperatures that can lead to decreased biological treatment, and high raw water turbidity levels that can lead to premature clogging of the filter and frequent cleaning requirements, resulting in increased risk of pathogen breakthrough. Multistage filtration, consisting of roughing filtration followed by slow sand filtration, can overcome these treatment limitations and provide a robust treatment alternative for surface water sources of variable water quality in northern climates, which typically experience water temperatures ranging down to 2C̊. Prior to this study, however, multistage filtration had yet to be systematically challenged in colder climates, including testing of its performance under increased hydraulic loadings and elevated influent turbidity together with cold water conditions. The primary goal of this research was to demonstrate the reliability of multistage filtration for small communities in northern climates with reference to the Ontario Safe Drinking Water Act. In this research, testing was conducted on two different pilot multistage filtration systems and fed with water from the Grand River, a municipally and agriculturally impacted river in Southern Ontario. One system featured pre-ozonation and post-granular activated carbon (GAC) stages, and shallower bed depths in the roughing filter and slow sand filter. The other system featured deeper bed depths in the roughing filter and slow sand filter, two parallel roughing filters of different design for comparison, and a second stage of slow sand filtration for increased robustness. Removal of turbidity, total coliforms, and fecal coliforms under a range of influent turbidities (1 to>100 NTU), water temperatures (~2 to 20C̊), and hydraulic loading rates (0.2 to 0.8 m/h) were investigated. In addition, the slow sand filters in each pilot system were challenged with high concentrations (~10¡ oocyst/L) of inactivated Cryptosporidium parvum oocysts. The performance of both pilot multistage filtration systems was highly dependent on the biological maturity of the system and its hydraulic loading rate. In a less mature system operating in cold water conditions (5C̊), effluent turbidity was mostly below 0.5 NTU during periods of stable influent turbidity (no runoff events) and a hydraulic loading of 0.4 m/h, however, runoff events of high influent turbidity (50 NTU), increased hydraulic loadings (0.6 m/h), and filter cleaning occasionally resulted in effluent turbidity above 1 NTU. Furthermore, in a less mature system operating during runoff events of high turbidity, reducing the hydraulic loading rate to 0.2 m/h was important for achieving effluent turbidity below 1 NTU. However, in a more mature system operating in warm water conditions (19-22C̊), effluent turbidity was consistently below 0.3 NTU at a hydraulic loading rate of 0.4 m/h, and below 0.5 NTU at 0.8 m/h, despite numerous events of high influent turbidity (>25 NTU). It remains to be seen whether this performance could be sustained in colder water temperatures with a fully mature filter. Removal of coliform bacteria was occasionally incomplete in a less mature multistage system, whereas, in a more mature system operating in warm water conditions (>9C̊), removal was complete in all measurements. Furthermore, the average removal of Cryptosporidium was greater than 2.5 logs in both systems (with hydraulic loading rates ranging from 0.4 to 0.8 m/h) and improved with increased filter maturity. Each individual stage of the multistage system was an important treatment barrier in the overall process of turbidity and pathogen removal. The roughing filter was not only important for protecting the slow sand filter from solids loading and increasing its run length, but was also a significant contributor to coliform removal when the system was less mature. Removal of turbidity was significantly improved when the roughing filter was more mature, suggesting that biological treatment was an important treatment mechanism in the roughing filter. Although pre-ozonation was used mainly for the removal of organic carbon and colour, it achieved complete removal of coliform bacteria and was also suspected to be important for enhanced removal of turbidity. The second slow sand filter in series provided additional robustness to the process by reducing effluent turbidity to below 1 NTU during cold water runoff events of high turbidity and increased hydraulic loadings (0.6 m/h), while achieving effluent below 0.3 NTU during normal periods of operation. It also provided additional removals of coliforms under challenging operating conditions, and contributed an additional average removal of Cryptosporidium of 0.8 logs, which resulted in cumulative removal of 3.7 logs, approximately 1 log greater than all the other challenge tests. Collectively, the entire multistage system performed well with water temperatures ranging down to 2C̊, limited filter maturity, elevated raw water turbidities, and increased hydraulic loading rates. Its ability to meet the current Ontario turbidity regulations and greater than 2 log removal of Cryptosporidium over a range of operating conditions, with little or no process adjustment, is a testament to the robustness and minimal maintenance requirements of the process, which are desirable attributes for small water systems that are often located in rural areas. While this research demonstrated the performance of multistage filtration using pilot scale testing, it is important to note that full-scale plants tend to produce significantly better results than pilot facilities, due to long term biological maturation of the system. Overall, multistage filtration is a sustainable and cost-effective technology that, through this research, appears to be a safe, reliable, and robust treatment alternative for small and non-municipal water systems in North America and the developing world. Further, based on its performance with challenging influent water quality and cold water conditions, multistage filtration holds particular promise for small communities in northern climates that are required to meet safe drinking water regulations, but are dependent on surface water sources of variable water quality and temperatures.
Summary Report
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Author :
language : en
Publisher:
Release Date : 1992
Summary Report written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1992 with Sewage categories.
Drinking Water Treatment Using Slow Sand Filtration
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Author : Kim Ray Fox
language : en
Publisher:
Release Date : 1987
Drinking Water Treatment Using Slow Sand Filtration written by Kim Ray Fox and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1987 with Water categories.
Drinking Water Treatment For Small Communities
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Author : United States. Environmental Protection Agency. Office of Research and Development
language : en
Publisher:
Release Date : 1994
Drinking Water Treatment For Small Communities written by United States. Environmental Protection Agency. Office of Research and Development and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1994 with Drinking water categories.
Recent Progress In Slow Sand And Alternative Biofiltration Processes
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Author : Rolf Gimbel
language : en
Publisher: IWA Publishing
Release Date : 2006-03-31
Recent Progress In Slow Sand And Alternative Biofiltration Processes written by Rolf Gimbel and has been published by IWA Publishing this book supported file pdf, txt, epub, kindle and other format this book has been release on 2006-03-31 with Science categories.
Slow sand filtration is typically cited as being the first "engineered" process in drinking-water treatment. Proven modifications to the conventional slow sand filtration process, the awareness of induced biological activity in riverbank filtration systems, and the growth of oxidant-induced biological removals in more rapid-rate filters (e.g. biological activated carbon) demonstrate the renaissance of biofiltration as a treatment process that remains viable for both small, rural communities and major cities. Biofiltration is expected to become even more common in the future as efforts intensify to decrease the presence of disease-causing microorganisms and disinfection by-products in drinking water, to minimize microbial regrowth potential in distribution systems, and where operator skill levels are emphasized. Recent Progress in Slow Sand and Alternative Biofiltration Processes provides a state-of-the-art assessment on a variety of biofiltration systems from studies conducted around the world. The authors collectively represent a perspective from 23 countries and include academics, biofiltration system users, designers, and manufacturers. It provides an up-to-date perspective on the physical, chemical, biological, and operational factors affecting the performance of slow sand filtration (SSF), riverbank filtration (RBF), soil-aquifer treatment (SAT), and biological activated carbon (BAC) processes. The main themes are: comparable overviews of biofiltration systems; slow sand filtration process behavior, treatment performance and process developments; and alternative biofiltration process behaviors, treatment performances, and process developments.
Management Of The Schmutzdecke Layer Of A Slow Sand Filter
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Author : Peter Livingston
language : en
Publisher:
Release Date : 2013
Management Of The Schmutzdecke Layer Of A Slow Sand Filter written by Peter Livingston and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with categories.
Slow sand filters (SSF) have been used to treat surface water to drinking water standards for over a century. Today many cities, including London still treat surface waters to drinking water standards, however because there are viruses that are not efficiently removed by a slow sand filter and are not killed by chlorine, communities have turned to the use of micro filtration and/or reverse osmosis to provide safe drinking water. These technologies are much more efficient if organics are removed and turbidity reduced to less than 1 Nephelometric Turbidity Units (NTU). The greenhouse industry is another potential user of slow sand filters. They are not able to recycle irrigation drainage water without it being treated to reduce bacteria, virus, and fungi. The objective of this research was to develop management strategies for SSF that specifically meet the needs of entities using SSF for pretreatment of potable water or use in a greenhouse. This data was used to test a scour system that resulted in scouring 80 percent of the organic layer in the filter and suspending the solids for 40 minutes. A conceptual design was done for a full scale SSF that took advantage of the scour and suspension data to clean the SSF at the end of a run cycle. SSF were able to consistently produce water with a turbidity less than 1 (NTU) and with the infiltration capacity of 0.27 m3m−2. For greenhouse effluent a 1,000 square meter greenhouse that is discharging 3,600 L d−1 of drainage water would require a 12.6 m2 SSF, and the SSF for the community requiring treatment of 4.7 million liters per day of raw water was 730 m2. The innovative cleaning system based on an air/water jet was developed to clean the SSF. Experiments were run to determine the amount of time that the solids were suspended and a scour system developed to exceed these times. The entire time for cleaning and recovery of the SSF was an average of 118 minutes for the greenhouse system and 170 minutes for the SSF serving a small community.
Multi Stage Filtration
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Author : Gerardo Galvis
language : en
Publisher:
Release Date : 1998
Multi Stage Filtration written by Gerardo Galvis and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1998 with Drinking water categories.
Drinking Water Treatment For Small Communities
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Author : United States. Environmental Protection Agency. Office of Research and Development
language : en
Publisher:
Release Date : 1994
Drinking Water Treatment For Small Communities written by United States. Environmental Protection Agency. Office of Research and Development and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1994 with Drinking water categories.
Slow Sand Filtration Treatment Of Agriculturally Impacted Water
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Author : Weixin Chen
language : en
Publisher:
Release Date : 2017
Slow Sand Filtration Treatment Of Agriculturally Impacted Water written by Weixin Chen and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with categories.
Agricultural runoff and influence to surface water is a widely experienced problem across the world, particularly in treating that water for potable consumption. Although many effective methods have been researched, there are few that can be considered suitable for rural regions, in-home and on-site water treatment, and extremely smallscale design without requiring significant chemical use, operator skills and sophistication, and large-scale to be economically viable. This research focuses on the use of slow sand filtration (SSF) as one of the most effective methods for potable water treatment that can meet all of the above criteria. The experiments were designed using rapid small scale column testing theory, which is a directly scalable approach to developing a robust and effective system for treating water. The SSF laboratory experiments were divided into two parts: preliminary experiments and full-scale experiments. The preliminary experiments were designed to test the removal efficiency of agriculturally-associated concentrations of orthophosphate and iron. The full-scale experiments were design simulate the realistic SSF plant which can test the removal efficiency with different concentration of additive in raw water. Raw water samples were collected from Wascana Lake as representative of complex water quality associated with both rural and urban contamination and agricultural influence. In the experiments, these raw water samples are subjected to several operational, water quality and environmental factors, including temperature, pH and filtration rate, to determine the impacts on removal efficiency and overall performance of the SSFs. The results of the preliminary experiments indicate that 25°C and alkaline conditions had the most significant impact on orthophosphate removal. Factors such as lower temperature (5°C) and acidic condition created an inhibited impact on the results, leaving higher concentration of orthophosphate in the effluent. For iron removal, the pH, temperature and filtration rate were all noted to impact removal efficiency. Higher temperature (25°C), increased alkalinity, and higher filtration rate resulted in higher effluent concentrations of iron. The results of the full-scale experiments indicate the interaction of phosphate, nitrate, iron and humic acids in SSF. The data show that increasing phosphate and nitrate in the raw water can slightly improve the performance of nitrate and phosphate removal but no obvious effect in humic acids and iron removal. The higher iron concentration can help improve humic acids removal. The experimental results clearly demonstrate that temperature and pH control in water treatment design are essential for high performance and robust and reliable production of high quality potable water.
Slow Sand Filtration Appropriate Technology For Safe Water International Reference Centre For Community Water Supply And Sanitation
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Author : International Reference Centre for Community Water Supply and Sanitation
language : en
Publisher:
Release Date :
Slow Sand Filtration Appropriate Technology For Safe Water International Reference Centre For Community Water Supply And Sanitation written by International Reference Centre for Community Water Supply and Sanitation and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on with categories.