The objective of this research project was to investigate the influence of the principal design and operational parameters on the quality of the filtrate from a slow sand filter. These parameters are sand effectivc size, depth of sand bed, rate of filtration, water temperature and influent quality. Attempts were then made to establish relationships between the variables employed by means of regression analyses of the experimental data. To carry out the investigation three laboratory scale filter columns were constructed each measuring 150 mm in diameter and 3010 mm height. The filtration medium in each column consisted of a 1.2 m depth of sand on a 0.3 m depth of gravel. For the three individual columns three different sand sizes were employed. These were 0.17 mm effective size (ES), 0.35 mm ES and 0.45 mm ES. Water to be filtered was abstracted from the Burleigh Brook, adjacent to the Civil Engineering laboratories. As required small amounts of settled sewage, obtained from the Loughborough Water Reclamation Works, were added to increase both the turbidity and the count of indicator bacteria. The filters were operated at five different filtration rates at three different temperatures. These temperatures were 25 degrees C, 15 degrees C, 5 degrees C and the filtration rates repeated for each temperature were 0.1, 0.2, 0.3, 0.4, 0.5 m/h. The filters were operated for not less than one month at each filtration rate. In order to assess the efficiency of the filters water samples were taken and analysed from the influent and from the filtrate and also from a series of sampling taps positioned at various depth down the sand media. These water samples were tested for total coliform bacteria, for faecal coliform bacteria, suspended solids and turbidity. Regression analyses were then carried out on the data obtained and regression models were developped for 100 mm and 1200 mm sand depths of each filter for each period. Occasional tests (i. e. at least once for each flow rate) were also carried out for nitrate and ammoniacal nitrogen, colour, pH, conductivity, total organic carbon (TOC) and dissolved oxygen. Following the completion of the filtration operation at three temperatures and five filtration rates the sands of the filtration media were also examined. Sand samples were taken for examination from 0, 50, 100, 150, 200, 300, 400, 600, 800, 1000 and 1200 mm below the sand surface of each filter. Then in order to assess both the penetration of the removed solids into the filter bed and to investigate the concentration of the biological film developed within the sand bed, sand samples were analysed for suspended solids, turbidity, standard plate count bacteria and particulate organic carbon. Regression analyses were also carried out on these data and variation of each parameter against each filter bed was modelled. The solid and biological deposits on the sand samples were also viewed with a Scanning Electron Microscope.

A study of the feasibility of lagoon-intermittent sand filter treatment of dairy wastewaters from the Utah State University dairy was performed from 1978 through 1980. The report also includes an analysis of alternative dairy wastewater treatment systems utilizing a computer model. A simple and inexpensive method of dairy wastewater treatment is needed so that the small (50- 300 cows) dairy farmer can meet the 30 mg/ ~ of BODs federal effluent standard and still earn a profit. The influent to the USU dairy treatment system, the lagoon effluent and the filter effluent were sampled during the summers of 1978 and 1979 for BOD s , suspended solids and volatile suspended solids . The data show t hat removal efficiencies over 90 percent were achieved by the lagoon-intermittent sand filter system, but the effluent BODs and suspended solids concentrations did not meet the federal standards. The high effluent concentrations were a. result of the lagoon being overloaded. The treatment system's construction allowed runoff, groundwater and milking center washwater to enter the lagoon causing greater than expected hydraulic and organic mass loading rates. Despite high influent concentrations the intermittent sand filters consistently removed 80 percent of the suspended solids from the lagoon effluent. If the quality of the lagoon effluent were improved by reducing the organic mass loading rate, the effluent from lagoon intermittent sand filter treatment of dairy wastewaters would meet the federal standards.

The purpose of the study is to find a suitable method for removal of iron and manganese considering local economic and environmental aspects. El Salvador is situated in Central America with a coast line towards the Pacific Ocean. The country borders Guatemala and Honduras. Aguilares is a town situated in the department of San Salvador, with a population of approximately 33,000 people. Currently, the population is provided with water for about two hours per day, since it is the highest capacity of the existing wells. During these two hours many households fill a small tank with water to use for the remainder of the day. The water is not safe to use for oral consumption because of the levels of bacteria and other contamination. One of the wells, situated in the community of Florída is not in use at this date because of the high levels of Iron and Manganese in the ground water which cannot be removed with the present technique.Ground water is naturally pure from bacteria at a depth of 30 m or more, however solved metals may occur and if the levels are too high the water is unsuitable to drink. The recommended maximum levels by WHO (2008) [1] for Iron and Manganese are 2 mg/l and 0.5 mg/l respectively.Literature and field studies led to the following results; Iron and manganese can be removed by precipitation followed by separation. Precipitation is achieved by aeration, oxygenation or chemical oxidation and separation is achieved by filtration or sedimentation.The different methods all have advantages and disadvantages. However the conclusion reached in this report is that aeration and filtration should be used in the case of Florída. What equipment and construction that should be used depends on economic and resource factors as well as water requirements, which is up to the council of Aguilares to deliberate.

This research aimed to address the knowledge gaps in the literature regarding the removal of waterborne pathogens (viruses and protozoa) by modified multistage slow sand filtration. In the current study, two pilot-scale multistage slow sand filtration systems were operated continuously for over two years. The pilot systems treated agricultural- and urban-impacted raw river water of variable quality with turbidity peaks over 300 NTU and seasonal cold temperatures <2??C. The first system (Pilot 1) consisted of two independent trains that included pre-ozonation, shallow-bed upflow gravel roughing filtration, and shallow-bed slow sand filtration. Pilot 1 was a pilot-scale version of an innovative, commercially available full-scale system. The second system (Pilot 2) included a full-depth upflow gravel roughing filter, a full-depth slow sand filter, and a second shallow-depth slow sand filter in series. The SSFs of both pilots were operated at high hydraulic loading rates (typically 0.4 m/h) at the upper limit of the literature recommended range (0.05 to 0.4 m/h). Both pilot systems provided excellent turbidity removal despite the high filtration rates. Effluent turbidity of all multistage SSF pilot systems were within the regulated effluent limits in Ontario for full-scale SSFs (below 1 NTU at least 95% of the time and never exceeded 3 NTU), despite raw water turbidity peaks over 100 NTU. The roughing filters contributed to approximately 60-80% of the full-train turbidity removal, compared to and 20-40% for the slow sand filters. On average, the second slow sand filter in pilot 2 provided almost no additional turbidity removal. The slow sand filter run lengths were short because of frequent high raw water turbidity, with about 50-80% of the runs in the range of 1-3 weeks. To prevent excessive SSF clogging and maintenance, filtration rates should be decreased during periods of high turbidity. Seven Cryptosporidium and Giardia challenge tests were conducted on the slow sand filters of both pilot systems at varying filtration rates (0.4 or 0.8 m/h), temperatures (2 to 25??C), and biological maturities (4 to 20 months). Removal of oocysts and cysts were good regardless of sand depth, hydraulic loading rate, and water temperature in the ranges tested. Average removals in the SSFs ranged from 2.6 to >4.4 logs for Cryptosporidium oocysts and ranged from >3.8 to >4.5 logs for Giardia cysts. This was consistent with findings in the literature, where oocyst and cyst removals of >4 logs have been reported. Cryptosporidium oocyst removals improved with increased biological maturity of the slow sand filters. At a water temperature of 2??C, average removal of oocysts and cysts were 3.9 and >4.5 logs, respectively, in a biologically mature SSF. Doubling the filtration rate from 0.4 to 0.8 m/h led to a marginal decrease in oocyst removals. Sand depths in the range tested (37-100 cm) had no major impact on oocyst and cyst removals, likely because they are removed primarily in the upper section of slow sand filter beds by straining. In general, good oocyst and cyst removals can be achieved using shallower slow sand filter bed depths and higher filtration rates than recommended in the literature. There are very few studies in the literature that quantify virus removal by slow sand filtration, especially at high filtration rates and shallow bed depths. There are no studies that report virus removal by slow sand filtration below 10??C. As such, 16 MS2 bacteriophage challenge tests were conducted at varying water temperatures (<2 to >20??C) and filtration rates (0.1 vs. 0.4 m/h) between February and June 2006 on biologically mature slow sand filters with varying bed depths (40 vs. 90 cm). Biologically mature roughing filters were also seeded with MS2. Average MS2 removals ranged from 0.2 to 2.2 logs in the SSFs and 0.1 to 0.2 logs in the RFs under all conditions tested. Virus removal by slow sand filtration was strongly dependant on hydraulic loading rate, sand depth, and water temperature. Virus removal was greater at a sand depth of 90 cm vs. 40 cm, at an HLR of 0.1 m/h vs. 0.4 m/h, and at warm (20-24??C) vs. cold (<2-10??C) water temperatures when sufficient warm water acclimation time was provided. Increased sand depth likely increased MS2 removal because of greater detention time for predation and greater contact opportunities for attachment to sand grains and biofilms. A lower HLR would also increase MS2 removal by increasing detention time, in addition to decreasing shear and promoting attachment to filter media and biofilms. Greater MS2 removal at warmer water temperatures was attributed to improved biological activity in the filters. Schmutzdecke scraping was found to have only a minor and short-term effect on MS2 removals. Virus removal can be optimized by providing deep SSF beds and operating at low filtration rates. Virus removal may be impaired in cold water, which could affect the viability of using SSF/MSF at northern climates if communities do not use disinfection or oxidation. As a stand-alone process, slow sand filtration (with or without roughing filtration) may not provide complete virus removal and should be combined with other treatment processes such as disinfection and oxidation to protect human health.

A presença de substâncias húmicas na água de abastecimento tem recebido a atenção de diversos pesquisadores nas últimas décadas, pois pode gerar subprodutos ao ser exposta a agentes oxidantes e desinfetantes. A filtração em múltiplas etapas (FiME) se apresenta como uma alternativa para realizar o tratamento de água de comunidades de pequeno porte, entretanto, a eficiência quanto à remoção de cor verdadeira associada ao carbono orgânico dissolvido ou às substâncias húmicas, tem sido questionada ou relatada como baixa. A filtração lenta com pré-ozonização vem sendo utilizada, pois o ozônio atua nas moléculas da matéria orgânica, aumentando sua biodegradabilidade e seus subprodutos desaparecem logo após a aplicação. A aplicação conjunta do ozônio e peróxido de hidrogênio, tem o objetivo de produzir espécies com radicais livres, de vida curta, que sejam altamente reativos e possam oxidar a maior parte das substâncias presentes na água natural. A presente pesquisa avaliou a remoção de substâncias húmicas na filtração lenta, utilizando para essa avaliação parâmetros indiretos como cor verdadeira, absorvância 254 nm e carbono orgânico dissolvido. Foram realizados cinco ensaios utilizando quatro filtros lentos, sendo dois com camada de carvão ativado granular (CAG), em que foram ensaiadas várias alternativas de pré-oxidação com ozônio e peróxido de hidrogênio. Obteve-se, como principal conclusão, que os filtros lentos com CAG, precedidos de oxidação com ozônio e depois peróxido de hidrogênio, em dosagens adequadas, apresentaram remoção média de cor verdadeira de 64% da cor inicial. Concluiu-se, também, que o peróxido de hidrogênio afeta o desenvolvimento da camada biológica, interferindo no desenvolvimento da perda de carga, na remoção de turbidez e na remoção de substâncias húmicas. / The presence of humic substances in the water of supply has been received attention of several researchers in the last decades, because it can generate by-products when being exposed to oxidants and disinfectant. The multistage filtration (FiME) is an alternative considered to achieve water treatment for small size rural communities, however, the efficiency with relationship to the removal of true color associated to the dissolved organic carbon or to the humic substances, it has been questioned or reported as low. The slow filtration with pre-ozonation is being used, since the ozone acted in the molecules of the organic matter of high molecular weight, increasing its biodegradability and by-products disappear soon after the application. The combined application of the ozone and hydrogen peroxide have the objective of producing species with free radicals, of short-lived, that are highly reagents and can oxidize most of the present substances in the natural water. The present research it evaluated the removal of humic substances in the slow sand filtration, using for that evaluation indirect parameters as true color, absorbance 254 nm and dissolved organic carbon. Five experiments were realized using four slow filters, being two with layer of activated carbon to granulate (CAG), in that several pre-oxidation alternatives were rehearsed with ozone and peróxido of hydrogen. It was obtained, as main conclusion that the slow filters with CAG preceded ofoxidation with ozone and hydrogen peroxide, in appropriate dosagens, presented medium removal of true color of 64% of the initial color. It was also concludes that the hydrogen peroxide interferes the development of the biological layer, interfering in the development of the loss of head, in the turbidity removal and in the removal of humic substances.

This research aimed to address the knowledge gaps in the literature regarding the removal of waterborne pathogens (viruses and protozoa) by modified multistage slow sand filtration. In the current study, two pilot-scale multistage slow sand filtration systems were operated continuously for over two years. The pilot systems treated agricultural- and urban-impacted raw river water of variable quality with turbidity peaks over 300 NTU and seasonal cold temperatures <2°C. The first system (Pilot 1) consisted of two independent trains that included pre-ozonation, shallow-bed upflow gravel roughing filtration, and shallow-bed slow sand filtration. Pilot 1 was a pilot-scale version of an innovative, commercially available full-scale system. The second system (Pilot 2) included a full-depth upflow gravel roughing filter, a full-depth slow sand filter, and a second shallow-depth slow sand filter in series. The SSFs of both pilots were operated at high hydraulic loading rates (typically 0.4 m/h) at the upper limit of the literature recommended range (0.05 to 0.4 m/h). Both pilot systems provided excellent turbidity removal despite the high filtration rates. Effluent turbidity of all multistage SSF pilot systems were within the regulated effluent limits in Ontario for full-scale SSFs (below 1 NTU at least 95% of the time and never exceeded 3 NTU), despite raw water turbidity peaks over 100 NTU. The roughing filters contributed to approximately 60-80% of the full-train turbidity removal, compared to and 20-40% for the slow sand filters. On average, the second slow sand filter in pilot 2 provided almost no additional turbidity removal. The slow sand filter run lengths were short because of frequent high raw water turbidity, with about 50-80% of the runs in the range of 1-3 weeks. To prevent excessive SSF clogging and maintenance, filtration rates should be decreased during periods of high turbidity. Seven Cryptosporidium and Giardia challenge tests were conducted on the slow sand filters of both pilot systems at varying filtration rates (0.4 or 0.8 m/h), temperatures (2 to 25°C), and biological maturities (4 to 20 months). Removal of oocysts and cysts were good regardless of sand depth, hydraulic loading rate, and water temperature in the ranges tested. Average removals in the SSFs ranged from 2.6 to >4.4 logs for Cryptosporidium oocysts and ranged from >3.8 to >4.5 logs for Giardia cysts. This was consistent with findings in the literature, where oocyst and cyst removals of >4 logs have been reported. Cryptosporidium oocyst removals improved with increased biological maturity of the slow sand filters. At a water temperature of 2°C, average removal of oocysts and cysts were 3.9 and >4.5 logs, respectively, in a biologically mature SSF. Doubling the filtration rate from 0.4 to 0.8 m/h led to a marginal decrease in oocyst removals. Sand depths in the range tested (37-100 cm) had no major impact on oocyst and cyst removals, likely because they are removed primarily in the upper section of slow sand filter beds by straining. In general, good oocyst and cyst removals can be achieved using shallower slow sand filter bed depths and higher filtration rates than recommended in the literature. There are very few studies in the literature that quantify virus removal by slow sand filtration, especially at high filtration rates and shallow bed depths. There are no studies that report virus removal by slow sand filtration below 10°C. As such, 16 MS2 bacteriophage challenge tests were conducted at varying water temperatures (<2 to >20°C) and filtration rates (0.1 vs. 0.4 m/h) between February and June 2006 on biologically mature slow sand filters with varying bed depths (40 vs. 90 cm). Biologically mature roughing filters were also seeded with MS2. Average MS2 removals ranged from 0.2 to 2.2 logs in the SSFs and 0.1 to 0.2 logs in the RFs under all conditions tested. Virus removal by slow sand filtration was strongly dependant on hydraulic loading rate, sand depth, and water temperature. Virus removal was greater at a sand depth of 90 cm vs. 40 cm, at an HLR of 0.1 m/h vs. 0.4 m/h, and at warm (20-24°C) vs. cold (<2-10°C) water temperatures when sufficient warm water acclimation time was provided. Increased sand depth likely increased MS2 removal because of greater detention time for predation and greater contact opportunities for attachment to sand grains and biofilms. A lower HLR would also increase MS2 removal by increasing detention time, in addition to decreasing shear and promoting attachment to filter media and biofilms. Greater MS2 removal at warmer water temperatures was attributed to improved biological activity in the filters. Schmutzdecke scraping was found to have only a minor and short-term effect on MS2 removals. Virus removal can be optimized by providing deep SSF beds and operating at low filtration rates. Virus removal may be impaired in cold water, which could affect the viability of using SSF/MSF at northern climates if communities do not use disinfection or oxidation. As a stand-alone process, slow sand filtration (with or without roughing filtration) may not provide complete virus removal and should be combined with other treatment processes such as disinfection and oxidation to protect human health.

Back grinding (BG) wastewater consists mainly of high-purity water and high concentrations of inorganic particles. If the BG wastewater could be treated and recycled efficiently, it should be sort of economic benefit. In this study, appropriate pre-treatment technologies are evaluated to obtain the feasible recycle system. From the chemical coagulation experiment, the addition of PAC or FeCl3, both of them can obviously reduce the turbidity and suspended solid concentrations (SS). In addition, polymer can advance the sedimentation process. Considering the cost of practical operation, the turbidity of BG waste water could be removed up to 97% by using polyaluminum chloride as the coagulant (2.2 mg/L) and polymer as the coagulant aid (0.5 mg/L) in the pH=7 condition . In sand filtration experiment, the turbidity and SS can¡¦t be effectively removed if the coagulation isn¡¦t used on BG wastewater. It demonstrates that BG wastewater contains high concentration of nano-scale particles. The rate of removable turbidity can reach 99% under applying coagulation, sedimentation, and sand filtration. In ultra-filtration experiment, both of spiral-wound (SW) and hollow-fiber (HF) can remove more than 99.9% of turbidity. For the flux of behavior, the performance of pre-treatment water is better than non-treatment water. Thus, it reveals that appropriate pre-treatment can lower the load of membrane filtration system. For the obtained recycle water, the grade of standard can achieve the grade of the cooling tower required. However, due to its high particle-containing characteristics, the commonly used reverse-osmoses (RO) membrane filtration technology can not be directly applied for purification process because the fouling/clogging problem would cause the frequent membrane replacement. In this lab-scale feasibility study, pre-treatment technologies (e.g., sand filtration, chemical coagulation, ultra-filtration) were applied to reduce the turbidity and particle concentrations of the BG wastewater (collected from a semiconductor manufacturing plant) before RO filtration unit. The BG wastewater contained turbidity and suspended solid concentrations of 3,200 NTU and 96 mg/L, respectively. The measured pH and conductivity of the BG wastewater were in the ranges of 6.8 to 7.2 and 14 to 18 £gS/cm, respectively. Moreover, the particle sizes of the solids varied from 300 to 700 nm. Thus, applying conventional sand filtration along could not effectively remove the nano-scale particles. Results from the chemical coagulation experiment reveal that the turbidity and particles of the BG wastewater could be significantly removed (up to 95% of turbidity and particle removal) by the coagulation/sedimentation process using polyaluminum chloride as the coagulant (2.2 mg/L) and polymer as the coagulant aid (0.5 mg/L). Results also indicate that up to 99% of turbidity and particle removal could be obtained with the application of ultra-filtration unit after the coagulation/sedimentation process. Results from this study indicate that applying appropriate pre-treatment technologies (coagulation and ultra-filtration) would lower the fouling rate and extend the life of RO membrane used for BG wastewater purification.

A presença de substâncias húmicas na água de abastecimento tem recebido a atenção de diversos pesquisadores nas últimas décadas, pois pode gerar subprodutos ao ser exposta a agentes oxidantes e desinfetantes. A filtração em múltiplas etapas (FiME) se apresenta como uma alternativa para realizar o tratamento de água de comunidades de pequeno porte, entretanto, a eficiência quanto à remoção de cor verdadeira associada ao carbono orgânico dissolvido ou às substâncias húmicas, tem sido questionada ou relatada como baixa. A filtração lenta com pré-ozonização vem sendo utilizada, pois o ozônio atua nas moléculas da matéria orgânica, aumentando sua biodegradabilidade e seus subprodutos desaparecem logo após a aplicação. A aplicação conjunta do ozônio e peróxido de hidrogênio, tem o objetivo de produzir espécies com radicais livres, de vida curta, que sejam altamente reativos e possam oxidar a maior parte das substâncias presentes na água natural. A presente pesquisa avaliou a remoção de substâncias húmicas na filtração lenta, utilizando para essa avaliação parâmetros indiretos como cor verdadeira, absorvância 254 nm e carbono orgânico dissolvido. Foram realizados cinco ensaios utilizando quatro filtros lentos, sendo dois com camada de carvão ativado granular (CAG), em que foram ensaiadas várias alternativas de pré-oxidação com ozônio e peróxido de hidrogênio. Obteve-se, como principal conclusão, que os filtros lentos com CAG, precedidos de oxidação com ozônio e depois peróxido de hidrogênio, em dosagens adequadas, apresentaram remoção média de cor verdadeira de 64% da cor inicial. Concluiu-se, também, que o peróxido de hidrogênio afeta o desenvolvimento da camada biológica, interferindo no desenvolvimento da perda de carga, na remoção de turbidez e na remoção de substâncias húmicas. / The presence of humic substances in the water of supply has been received attention of several researchers in the last decades, because it can generate by-products when being exposed to oxidants and disinfectant. The multistage filtration (FiME) is an alternative considered to achieve water treatment for small size rural communities, however, the efficiency with relationship to the removal of true color associated to the dissolved organic carbon or to the humic substances, it has been questioned or reported as low. The slow filtration with pre-ozonation is being used, since the ozone acted in the molecules of the organic matter of high molecular weight, increasing its biodegradability and by-products disappear soon after the application. The combined application of the ozone and hydrogen peroxide have the objective of producing species with free radicals, of short-lived, that are highly reagents and can oxidize most of the present substances in the natural water. The present research it evaluated the removal of humic substances in the slow sand filtration, using for that evaluation indirect parameters as true color, absorbance 254 nm and dissolved organic carbon. Five experiments were realized using four slow filters, being two with layer of activated carbon to granulate (CAG), in that several pre-oxidation alternatives were rehearsed with ozone and peróxido of hydrogen. It was obtained, as main conclusion that the slow filters with CAG preceded ofoxidation with ozone and hydrogen peroxide, in appropriate dosagens, presented medium removal of true color of 64% of the initial color. It was also concludes that the hydrogen peroxide interferes the development of the biological layer, interfering in the development of the loss of head, in the turbidity removal and in the removal of humic substances.

No description available.

In recent decades, most countries of the world have experienced a shortage of water and increase its rate of consumption. Today, every country in the world are interested in this problem by trying to find alternatives to address this shortage. One solution is reuse greywater (GW) for irrigation after treatment. GW is all water generated from Household except toilet water. The risks associated with the reuse of these waters are the presence of pathogens that can infect humans, animals and plants. In this thesis focused on studying treatment by slow sand filtration and the survival of representatives of pathogens, such as E. Coli, P. aeruginosa , E. Faecalis and Bacteriophage MS2 which could be found in the greywater. The study factors was a physico-chemicals factors such as; temperature (6±2,23±2,42±2°c), salinity (1.75 and 3.5% Nacl), oxygen (aerobic and anaerobic condition), nutrient ( rich media , 50%: 50% salt and poor media ), light with photocatalysis ( UV and Visible lights) and slow sand filter (Egyptian desert sand and swimming pool sand). A combination of high temperature, sunlight and photocatlysis are mainly responsible for the rapid decline of bacteria and MS2 coliphage. Slow sand filter have clearly less influence on the survival of bacteria in the greywater, but it effective to decline turbidity and COD for short times.