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Slow sand filtration for small water systems

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Abstract

For over 150 years, slow sand filters have been an effective means of treating water for control of microbiological contaminants. Slow sand filters do not need constant operator attention, making them an appropriate technology for water systems that are small or that employ part-time operators. During the 1970s through the 1990s, research and field evaluations of slow sand filtration have demonstrated its efficacy for control of microbiological contaminants that were unknown in the 1800s. In addition, pretreatment processes such as roughing filters and pre- ozonation have been developed or adapted for use with slow sand filters, increasing the range of source waters that can be treated and the number of contaminants that can be removed in slow sand filters. Inclusion of a layer of granular-activated carbon in a slow sand filter bed has improved capability for control of synthetic organic chemicals. This paper reviews design concepts and process capabilities for slow sand filters and discusses recent innovations in slow sand filter design that now enable this technology to be applied more widely than would have been appropriate two decades ago.

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... Under appropriated circumstances slow sand filters can be the simplest and cost-effective way of treatment, with some peculiarities implied that prevents its wider use [8]. There is a limited range of suitable water quality, as generally there is no chemical pre-treatment, and is not recommended to apply residual oxidant such as chloride, previously to filtration. ...
... The filtration rate calculated shows that under the current conditions the filter is by far overloaded and therefore does not fit the standards recommended by the Ministry of Health [11] for potable water. Slow sand filters are suitable for small communities and therefore small systems [8]. In the principle, Nova Crixás was adapted to this concept and therefore did not demanded a more sophisticated system. ...
... Alongside with the low filtering capacity, another disadvantage of the slow sand filters is that, in order to broaden the range of source water that can be successfully treated in the units, it is recommend [8] to combine pre-ozonation or roughing filters in the treatment. ...
Article
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To elaborate efficient and economical water supply systems is one of the main objectives in the sanitation companies water system projects. In order to address the challenges faced in reaching this objective, this study aims to identify, first, the relation between the percentage of non-conformed samples in treated water and the inefficiency of the filtering units installed in the water treatment plant, and second, if, by drawing the consumption variation curve it is the most efficient way to predict the storage tanks volume—comparing necessary capacity, determined by the consumption curve, and installed capacity, predict by the outdated Brazilian normative. In order to reach answers for these two questions, this study measured the operating efficiency of the treatment plant as well as have set a quantitative comparison between the two dimensioning criteria for storage tanks volume present in the literature. As a result, the analysis provided the authors to detect a focus of contamination in the single-layered filtering units, limited by the filtering capacity of 2–6 m³/(m² day), whilst operating at 333.13 m³/(m² day). As well as to detect by the drawing of the consumption variation curve an oversize of 68% and 60% in the dimensioning of the studied storage tanks. With the results provided by this analysis approach, it was possible to efficiently detect and correct critical impairments in the treatment phase and to conclude that a long-term analysis should be drawn in order to affirm if the consumption variation curve is the best design methodology for the reservoirs.
... [43][44][45] Low hydraulic loading rates (HLRs) and extended contact times (relative to classical biofiltration) promote biodegradation of DOC, even without chemical or energyintensive pre-treatments such as coagulation or preozonation. 46,47 Thus, biological filtration with relatively long contact times is the most likely design configuration to enable demonstration of treatment resilience in buffering elevated source water DOM resulting from wildfire ash because kinetic limitation is practically precluded-a proof-of-concept evaluation was the focus of this investigation. Specifically, the resilience of biological filtration treatment in reducing elevated/altered post-fire DOC resulting from wildfire ash was investigated. ...
... Bench-scale SSFlike biofilters with low HLRs and extended contact times (relative to classical biofiltration) were used because they represent operational scenarios in which maximal biodegradation of DOC would be expected. 46,47 The suitability of using benchscale biofilters to reasonably represent aspects of pilot-and full-scale biological filtration performance such as the ability to remove dissolved contaminants is generally understood [55][56][57] and has gained renewed interest in recent years. 58,59 Thus, this approach was used here and enabled duplicate evaluation of several source water quality ash content scenarios and disturbance periods. ...
Preprint
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Elevated/altered levels of dissolved organic matter (DOM) in water can be challenging to treat after wildfire. Biologically-mediated treatment removes some DOM; its ability to remove elevated/altered post-fire dissolved organic carbon (DOC) resulting from wildfire ash was therefore investigated. The treatment of low, medium, and high wildfire ash-amended source waters by bench-scale biofilters was evaluated in duplicate. Turbidity and DOC were typically well-removed during periods of stable operation (effluent turbidity ≤ 0.3 NTU in 93% of samples, average DOC removal ~20% in all biofilters during periods of non- impaired DOC removal). Daily DOC removal across all biofilters was generally consistent, suggesting that the wildfire ash and associated water extractable organic matter did not reduce the DOC biodegradation capacity of the biofilters. DOM fractionation indicated that this was because the low molecular weight neutral (which are known to be readily biodegradable) and biopolymer fractions of DOM were reduced; however, humics were largely recalcitrant. Thus, biological filtration may be resilient to wildfire ash-associated DOM threats to drinking water treatment. However, operational resilience may be compromised if the balance between readily removed and recalcitrant fractions of DOM change, as was observed when baseline source water quality fluctuated for brief periods during the investigation.
... High turbidity is generally the product of a hydrological or climatic phenomenon, such as heavy rains, which makes it necessary to increase the frequency of maintenance of the filtration system (Ranjan and Prem, 2018). A slow filter loses functionality with turbidity greater than 20 or 30 NTU, which is very problematic, if it is necessary to work with peaks of 50 to 100 NTU (Logsdon et al., 2002b;Ellis and Wood, 2009;Gottinger et al., 2011). In contrast, rapid sand filtration allows treating high turbidity raw water and the effluent is of very good quality, complying with stricter specifications, allowing changes in turbidity and filtration rates (Al-Rawi, 2017). ...
... In the SF there was a reduction in turbidity by 88.69%, while in the conventional plant the removal of turbidity was 98.75%, which corroborates what was reported by Al-Rawi (2017); Laghari et al. (2018). The color was reduced by 90.33% in the SF, coinciding with what was mentioned by certain authors, who indicate that the color is not as removed as efficiently in slow filters (Logsdon et al., 2002b;Gottinger et al., 2011). In contrast, the removal of color in the conventional system was 99.82%. ...
Article
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Safely managed drinking water for all is the United Nations Sustainable Development Goal 6.1. Achieving this goal is a challenge in rural areas. A strong partnership between users of a water treatment system was critical to the success of community-scale technological change. In this study, the efficiency of a water treatment system was evaluated after the implementation of a technological change in a rural area. This research was carried out in a community in Ecuador, which before the change in technology had a treatment system composed of gravel pre-filtration and slow filtration. This system did not guarantee adequate water quality, due to a notable increase in the color and turbidity levels of raw water; in addition to the growing demand for water in recent years. A new conventional treatment system was implemented consisting of: coagulation, flocculation, sedimentation, rapid filtration and disinfection. All the modernization works were carried out on the same infrastructure that had served as gravel pre-filters. Before modernization, samples of raw water and treated water were collected for six months. After the changes carried out, samples of raw and treated water were also collected for another six months. The parameters analyzed were: turbidity, color, pH, total dissolved solids, residual chlorine, nitrates, sulfates, phosphates, chlorides, alkalinity, total hardness and iron. The values of all the parameters analyzed improved after the modernization, indicating that the changes made in the treatment plant were successful. As a result, a conventional treatment to make water potable in rural areas has become a robust process that can operate within a wide range of water quality, improving the quality and quantity of drinking water.
... a filtração lenta é uma tecnologia considerada eficiente, de simples construção e manutenção, podendo ser utilizados recursos locais e sem dosagem de produtos químicos em sua operação ( GimBeL;GraHam;CoLLinS, 2006). assim, são excelentes alternativas para o abastecimento de água em áreas rurais em escala domiciliar ou para pequenas comunidades (LoGSdon; KoHne;aBeL, 2002). a raspagem da areia na superfície do filtro é o método de limpeza mais usual. ...
... a filtração lenta é uma tecnologia considerada eficiente, de simples construção e manutenção, podendo ser utilizados recursos locais e sem dosagem de produtos químicos em sua operação ( GimBeL;GraHam;CoLLinS, 2006). assim, são excelentes alternativas para o abastecimento de água em áreas rurais em escala domiciliar ou para pequenas comunidades (LoGSdon; KoHne;aBeL, 2002). a raspagem da areia na superfície do filtro é o método de limpeza mais usual. ...
Book
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O presente caderno técnico trata-se da apresentação da tecnologia de filtração lenta com retrolavagem, uma alternativa para a limpeza de filtros lentos. Essa concepção de filtros lentos é resultado de anos de pesquisa desenvolvida na Universidade Federal de Santa Catarina pelo Grupo de Pesquisa em Tratamento de Água no Laboratório de Potabilização das Águas. Em parceria com a Fundação Nacional de Saúde, por meio do Programa de Pesquisa em Saúde e Saneamento, foi realizado um projeto sobre a remoção de protozoárias em filtros lentos retrolaváveis onde também foram avaliados seus custos e propostas de aplicação que, somado aos 15 anos de pesquisa anteriores, resultaram nesse caderno. Espera-se que a tecnologia possa ser esclarecida e disseminada com o objetivo de facilitar a operação de filtros lentos em diversas escalas de aplicação, melhorando o acesso a água de boa qualidade aos usuários por meio de um sistema de tratamento simples, de fácil replicação, operação e manutenção. Portanto, primeiramente apresenta-se a filtração lenta de maneira geral e resumida como embasamento à técnica. Em sequência é discutida a filtração lenta com retrolavagem (foco do caderno), seus avanços e sugestões de aplicação, acompanhadas de roteiros de cálculos e parâmetros ideais de projeto.
... Rapid sand filters are depth filters, where the entire medium column is active in the capture of particles. In conventional drinking water production plants for surface water treatment, chemical coagulation, mixing, flocculation, and sedimentation are required upstream of the filters to achieve treatment goals pertaining to removal of suspended and colloidal matter (Logsdon et al., 2002). This complex scheme is not common in flow through aquaculture farms because of less stringent water quality requirements and of the high costs and operational complexity. ...
... These filters were first employed in Europe during the 19th Century for drinking water production. These filtration systems combine effective abatement of suspended and dissolved matter with biological removal of biodegradable organic matter (Campos et al., 2002;Logsdon et al., 2002;Huisman and Wood, 1974;Joubert and Pillay, 2008). They are simple to operate, do not require chemicals, and do not consume large amounts of electricity, relying on gravity for driving filtration (Huisman and Wood, 1974). ...
Article
A rapid sand filter (RSF, 12 m ³ m ⁻² h ⁻¹ ) and a rapid sand filter followed by slow sand filter (RSF-SSF, 0.1 m ³ m ⁻² h ⁻¹ ) were compared to investigate whether the biological activity in the RSF-SSF would improve turbidity reduction and control of biofilm growth in seawater aquaculture of juvenile dusky grouper over a 31 days test period. The RSF-SSF combination produced water with lower turbidity than RSF, turbidity breakthroughs in RSF were effectively abated by SSF. Microbial growth potential (MGP) measured by a growth assay with Pseudoalteromonas spongiae in samples filtered through 0,2μm membranes was significantly smaller in SSF filtrate (MGP, 3.2 ± 0,1 logCFU) than in RSF filtrate (3.9 ± 0,6 logCFU). Turbidity in fish tanks fed with RSF-SSF and RSF effluent remained below 1 NTU and 6 NTU, respectively, inspite of the large amount of food not consumed by the fish and of the tanks remaining open to the atmosphere. Surface biofouling on PVC samples was assessed by protein and carbohydrate analysis. It was less pronounced on bottoms of tanks operated with RSF-SSF treated water but similar on tank walls for both types of water. Carbohydrates were present in much larger quantities than proteins in bottom biofilms, but the opposite occurred in wall biofilms. Diatoms were dominant in RSF but not in RSF-SSF tank biofilms. Dusky grouper survival and growth was similar for the two types of water. The benefit of reduction of microbial growth potential achieved in SSF pretreatment was successfully captured in lesser tank surfaces biofilm colonization and by lower water turbidity in the tanks.
... Ainda assim, a filtração lenta resistiu ao longo dos anos, tanto no abastecimento público como nas pesquisas. Novos modelos de filtros foram desenvolvidos, alterando a operação ou características dos filtros, como o emprego de retrolavagem para a limpeza (MICHELAN et al., 2011;PIZZOLATTI et al., 2014;SOARES et al., 2010;SOUZA et al., 2016), uso de mantas sintéticas e o uso de carvão ativado granular para o emprego da adsorção (BAUER et al., 1996;CARNEIRO et al., 2016;DI BERNAR-DO;BRANDÃO;HELLER, 1999;LOGSDON;KOH-NE;ABEL, 2002). Diversos estudos foram desenvolvidos nos últimos anos a respeito do potencial de remoção de compostos dos quais ainda não se havia conhecimento, os chamados contaminantes emergentes. ...
... Ainda assim, a filtração lenta resistiu ao longo dos anos, tanto no abastecimento público como nas pesquisas. Novos modelos de filtros foram desenvolvidos, alterando a operação ou características dos filtros, como o emprego de retrolavagem para a limpeza (MICHELAN et al., 2011;PIZZOLATTI et al., 2014;SOARES et al., 2010;SOUZA et al., 2016), uso de mantas sintéticas e o uso de carvão ativado granular para o emprego da adsorção (BAUER et al., 1996;CARNEIRO et al., 2016;DI BERNAR-DO;BRANDÃO;HELLER, 1999;LOGSDON;KOH-NE;ABEL, 2002). Diversos estudos foram desenvolvidos nos últimos anos a respeito do potencial de remoção de compostos dos quais ainda não se havia conhecimento, os chamados contaminantes emergentes. ...
Article
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A filtração lenta é uma técnica simples para o tratamento de água e uma das mais antigas utilizadas no abastecimento público. Com o tempo, essa tecnologia perdeu espaço para sistemas que demandam, relativamente, menor área útil de ocupação, como a coagulação e a filtração rápida ou direta. Portanto, considera-se que há pouca informação sobre o uso atual dessa técnica de filtração para estudos na área. Em vista disso, esse estudo foi realizado com o intuito de fazer um levantamento e diagnóstico do uso da filtração lenta no estado de Santa Catarina. Estações de tratamento de água com filtros lentos foram identificadas e visitadas em todo o estado; os resultados de questionários aplicados in loco e observações em visitas técnicas são apresentados. Embora simples, observou-se que os problemas encontrados na aplicação da tecnologia estão relacionados à falta de conhecimento específico sobre o assunto. Concluiu-se que a filtração lenta ainda é aplicada no estado e a disseminação de conhecimento sobre a tecnologia é de suma importância para sua preservação, manutenção, melhor aplicação e disseminação em prol de seu uso.
... About 500,000 people worldwide depend on BSF for safe drinking water supply and its efficiency on faecal coliform (FC) and Escherichia coli removal have been documented (Duke et al. 2006;Stauber et al. 2006;Elliott et al. 2008). The growing interest to application of sand filters in water quality improvement is due to their low cost, convenient operation and easy maintenance while achieving high treatment efficiency (Logsdon et al. 2002;Nassar & Hajjaj 2013;Haig et al. 2014). These attributes make sand filters as cost effective technology to treat contaminated water in rural areas (Aslan & Cakici 2007;Langenbach et al. 2009). ...
... Several authors have reported the efficiency of sand filters in removing different contaminants in water to be between 90 to 99% (pathogenic bacteria) by 85-90% (viruses), 87-96% (turbidity), 94-99% (nitrate) and .99.9% (protozoans) (Stauber et al. 2006;Aslan & Cakici 2007;Elliott et al. 2008;Jenkins et al. 2011;Mahmood et al. 2011;Kennedy et al. 2012;Mwabi et al. 2013;Young-Rojanschi & Madramootoo 2014). Nevertheless, their treatment efficiency can decrease with high turbid water (.10-50 NTU), high organic loading and high amount of microorganisms in raw water because, they tend to clog the filters and decrease the filter run time and treatment efficiency (Logsdon et al. 2002;Ray & Jain 2011). Therefore, the need for a reliable pretreatment technology before using sand filters is inevitable. ...
Article
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The feasibility of constructed wetland integrated with sand filters (CW-SFs) for treating high turbid water for drinking was investigated. Turbid water of >1,000 NTU from Nadosaito dam in Monduli District, Tanzania was used. Along with turbidity; faecal coliform (FC), chemical oxygen demand (COD), total suspended solids (TSS) and nitrate removal were investigated. Furthermore, determination of optimal retention time for pollutants removal to acceptable levels was assessed at retention times of 0.5 to 5 days. Horizontal subsurface flow constructed wetland (HSSFCW) was used as pretreatment stage prior to biosand or slow sand filters. Results showed that HSSFCW produced effluent turbidity of <10–50 NTU at retention time of 3 days. Moreover, integrated CW-BSF needed a total retention time of 5 days to produce effluent of turbidity (0 NTU), FC (0 CFU/100 ml), COD (6.25 mg/L), TSS (0.5 mg/L) and nitrate (4.2 mg/L) whereas, CW-SSF needed 7 days to produce effluent of turbidity (0.6 NTU), FC (0 CFU/100 ml), COD (6.5 mg/L), TSS (1 mg/L) and nitrate (1.79 mg/L), which met drinking water standards of Tanzania Bureau of Standards (TBS) and World Health Organization (WHO). CW-BSF showed better performance than CW-SSF therefore, its application can enhance the availability of potable water in Tanzania rural communities.
... Moreover, with longer filter runs, the need for frequent cleaning of the slow sand filter is reduced, allowing enough time for biological maturation between cleaning sessions, which would otherwise lead to an increased risk of pathogen breakthrough (Cleary 2005). The range of source water quality that can be successfully treated using slow sand filters is also widened once roughing filtration of the influent is employed as a pretreatment stage for slow sand filtration (Logsdon et al. 2002). However, roughing filtration systems should only be deployed for influent turbidity .50 ...
Article
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A downward roughing filter unit consisting of silica sand as the filter medium was optimized for performance towards removal of turbidity and suspended solids from handwashing wastewater. Design-Expert software was employed to optimize media particle size, filter depth, and flowrate. Linear and quadratic models were found to best fit the responses of turbidity and suspended solids removal, respectively. Particle size and flow rate were the only parameters with significant effects on removal of turbidity and suspended solids. Optimal conditions were found to be media particle size 0.6 mm, filter depth 12 cm, and flow rate 0.3 Lmin−1, corresponding to removal efficiencies of 62 and 67% for turbidity and total suspended solids (TSS), respectively, as predicted by the model. Validation of model at optimal conditions resulted in turbidity and TSS removal of 55 and 53%, respectively. Additionally, removal efficiencies of the roughing filter towards apparent colour, true colour, biochemical oxygen demand (BOD5), and chemical oxygen demand (COD) from handwashing wastewater were 56, 20, 32, and 5%, respectively. Overall, although turbidity of filtered water was >50 NTU, the reduction achieved by roughing filtration is a significant step in enhancing the performance of water treatment processes downstream, including filtration and adsorption by slow sand filters and activated carbon, respectively. HIGHLIGHTS Downward roughing filter was optimized for pretreatment of handwash wastewater.; RSM was employed to optimize filter media size, depth, and flowrate.; Optimized system attained turbidity and TSS removal of 55 and 53%, respectively.; Roughing filtration to enhance the performance of downstream treatment processes.; Results contribute to design of treatment systems for onsite water recirculation.;
... Household filtration systems for safe drinking water provision include slow sand filters [7][8][9], ceramic filters [10][11][12], filters containing bone char [13,14], filters containing biomaterials such as biochar [15][16][17], filters containing geomaterials such as laterite [18][19][20], and hybrid filters containing combination of materials [21][22][23]. The household slow sand filter is known as biological sand filter (BSF) and has been successfully used in the developing world since the 1990s [8,24,25]. ...
Article
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This article critically evaluates the conventional Kanchan Arsenic Filter (KAF) in order to determine the main reasons for the reported poor performance. The KAF was introduced in 2004 in Nepal, and makes use of non-galvanized nails as a Fe0 source for As removal. As early as 2009, the KAF was demonstrated to be ineffective for As removal in many cases. This was unambiguously attributed to the Fe0 layer which is placed on top of a sand filter instead of being incorporated into a sand matrix. Despite this conceptual mistake, the conventional KAF has been largely distributed in Asia, and recent articles have assessed its sustainability. This study reiterates that the suitability of the technology rather than its sustainability should be addressed. Evidence shows that the KAF has the following design limitations: (i) uses iron nails of unknown reactivity, and (ii) operates on the principle of a wet/dry cycle. The latter causes a decrease in the corrosion rate of the used nails, thereby limiting the availability of the iron corrosion products which act as contaminant scavengers. Taken together, these results confirm the unsuitability of the conventional KAF. Besides correcting the design mistakes, more attention should be paid to the intrinsic reactivity of the used iron nails, including using alternative Fe0 materials (e.g., iron filings, steel wool) for filters lasting for just 6 or 18 months. Specific design considerations to be addressed in the future are highlighted
... Municipal waste water is processed with the help of biofilms, which are optimized in activated sludge plants by flocular operation. The slow-sand filters that use biofilms are used to remove organic components and heavy metals from lakes and rivers (Logsdon et al., 2002) Due to various metabolic processes in which ammonia is anaerobically oxidized to dinitrogen, biofilms that comprise planctomycetes in marine waters have the ability to extract nitrogen from waste water (Kartal et al., 2010). Biofilms play a significant role in water reclamation and reuse technologies and degrade toxic organic pollutants into harmless inorganic matter more commonly in water treatment systems. ...
Research
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Biofilms are the consortium of microorganisms encased within the slimy sheath of Extracellular Polymeric Substance. These are rampant in nature, comprising a pivotal strategy used by microbes to endure severe environmental conditions. The microorganisms inhabiting the biofilms display a stratified structure, in which the role of every species is fixed and predetermined as per the environmental suitability and synchronization. The role of quorum sensing in facilitating the communication processes in biofilms in magnificent. Biofilms can have positive impacts as well as negative repercussions, particularly with respect to industrial setting or on medical devices. In recent years, the role of biofilms in bioremediation has been realized and its potential for bioremediation is enormous and magnificent with respect to water, soil and air. The only prerequisite for optimising such things is that the complete microbial profile, architecture and kinetics of biofilms should be known. The role of biofilms in bioremediation has attracted the role of microbiologists towards this field because of its widespread application in environment, industry and health.
... Since microorganisms and suspended particles must travel more through the sand at higher sand depths, a greater removal efficiency can be expected (Ellis, 1984). Slow sand filters have been used in both developed and developing countries to remove bacteria from contaminated groundwater, especially in rural communities due to low operating costs, ease of use, and ease of maintenance [16,17]. ...
Article
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Scarcity of fresh drinking water has become a major concern in various parts of the world recently. Therefore, this study aimed to develop a sustainable polymer (polypropylene) and carbon (activated carbon from coconut shell) based water treatment filter. The filter was made by integrating polypropylene nonwoven fabric on the top of a two-inch layer of activated carbon and the traditional slow sand filter. The filter showed a significant reduction in turbidity, total dissolved solids (TDS), biological oxygen demand (BOD), pH, and concentration of heavy metals (HM) in the water samples collected from Turag River, Bangladesh. The reduction efficiencies were more than 85%. The higher value of reducing heavy metals, TDS, BOD, and pH might be explained by a higher particle retention and adsorption capacity of the filter due to the notable higher specific surface area of activated carbon and the pore size of the polypropylene filtration layer. The concentrations of lead, zinc, iron, potassium, magnesium, calcium, and copper were examined in which the filter showed a promising result; however, the removal efficiency of other potential heavy metals is yet to be tested.
... The slow sand filter (SSF) is traditionally designed as the most suitable potable water treatment unit in rural regions and equipped with a sand bed initially about 1 m deep and about 1 m of supernatant water (Logsdon et al., 2002). The effective size of sand grain may vary from 0.15 mm to 0.35 mm, and the uniformity coefficient should be less than 5 (preferably below 3). ...
Article
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This research aimed to investigate the optimum conditions of slow sand filter (SSF) media modification by using ground Anadara granosa shell waste and the effect of the ripening period on the total coliform (TC) removal efficiency. The response surface methodology with the central composite design was conducted with three factors, namely, seeding time (2–3 weeks), running time (0–20 days), type of SSF media (i.e., river sand, A. granosa shell, and their combination), as independent variables. The results showed that the ripening period factor interacted insignificantly by improving the TC removal efficiency due to short ripening time (p > 0.05). The optimum conditions of the SSF to achieve maximum TC removal efficiency (99.70% ± 21.50%) were as follows: combination media of river sand and ground A. granosa shell waste, 2.8 weeks (20 days) of ripening period, and 20 days of operation. In conclusion, the optimum operating parameters of the slow sand filter revealed that the combination of river sand and A. granosa shell as well as prolonged ripening and running times could increase the removal efficiency of TC. Hence, the A. granosa shell has good application potential as filter media to remove TC from the municipal wastewater.
... Slow sand filter is a biological method to treat water. Basically, this method only requires a container filled with one layer of sand followed by a layer of gravel that serves as a filter to treat water (Logsdon, 2002). This cost saving system is not only easy to design but also works effectively in filtering water for residents up to 5,000 people (WHO, 2000). ...
Conference Paper
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Metaldehyde is widely applied in the agricultural sector, largely in the removal of snails and slugs. Its water-soluble characteristic causes the compound to end up in our watery system. This is very dangerous as it is able to pollute drinking water and food source; thus adversely affect our health. Hence, removing metaldehyde is an important task for those involved with the treatment of water. For this reason, this paper gathers nine various methods which are proposed and used in treating water contaminated with metaldehyde. The simple but significant explanation will be able to assist those who are new in the fields of pesticide removal and water treatment. In parallel, it will be the basis for more advanced researches in the future.
... Meanwhile, point-of-entry is a water treatment system carried out before water enters the household water system [4][5][6]. Some of the technologies used in point-of-use systems are chlorination, coagulation, solar disinfection, ceramic water filter, bio-sand filter [7], membrane filtration, fibre/fabrics filter [3,8,9], and intermittent slow sand * Corresponding author: ekha.yogafanny@mail.ugm.ac.id filtration [10][11][12][13]. Moreover, a new-promising technology called pervious concrete filter (PCF) can be used to reduce turbidity from the water reaching 95% efficiency [14]. ...
Article
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The need for drinking water with affordable access is increasing nowadays. The poor water quality problems can be solved by several water treatment methods, i.e. ceramic filter (CF) and pervious concrete filter (PCF). Those two mentioned technologies work based on the pores that exist within the filter. This study aimed to review (1) the influence of the material composition of the CF and PCF on hydraulic characteristics (porosity, permeability, pore size, pore structure, pore connectivity/ distribution) and its removal effectiveness, and (2) the removal mechanisms of suspended solids and bacteria based on its hydraulic characteristics. The study reviewed 45 literature, including books, reports, and published articles. The type, mineral, and sources of clay and the type, shape, proportion, and size of combustible materials on CF will affect its hydraulic characteristic. The shape, size, and type of aggregate, the ratio of water to cement, and the ratio of aggregate to cement on PCF will affect its hydraulic characteristics. The removal mechanisms of suspended solids are straining on the surface and trapping on the deadlocked pores. On the other hand, the bacteria removal mechanisms strain the bacteria in the dirt layer and trap the bacteria in the pores.
... For the removal of metal ions and phosphate ion from the wastewater, the process of phytoremediation using T. latifolia and C. indica has been demonstrated. The partially purified water is further purified by passing it through sand filter prepared by arranging various layers of gravels and sand one over the other (Li Fangyue and Wichmann 2009;Logsdon et al. 2002;Manios et al. 2003). The water is allowed to pass through the filter at a very slow rate, and as water slowly percolates through a bed of carefully arranged sand medium, almost all the suspended and colloidal material is trapped by the top layers of sand. ...
Article
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The canteen and laboratory of every academic organization need a lot of clean water, and it generates equivalent amount of wastewater every hour which is neither purified nor reused. Due to water scarcity, the recycling and reusing of wastewater become very essential. The present study describes the simple and cost-effective method for the design of a small-scale wastewater treatment plant for the purification of wastewater generated by household, canteen and laboratory of an academic institute. The current study explored the process of phytoremediation by Typha latifolia L. and Canna indica L. for removal of metal ions and phosphate ions from the wastewater. The partially treated water after phytoremediation was further purified by sand filtration. The various water quality parameters (pH, hardness, dissolved oxygen, chemical oxygen demand, turbidity, total dissolved solids and metal ions) of the treated and untreated water were analyzed. It was observed that there are significant reduction in hardness, turbidity and chemical oxygen demand and increase in dissolved oxygen value. The treated water can be reused for various household works and agriculture.
... In [10], the authors summarized the advantages of using slow-sand filters ASTESJ ISSN: 2415-6698 in two major points: first, acceptable levels of treated water quality, and second, low cost and easy of construction. While the disadvantages of slow-sand filters were cited by [11]: ...
... The SSF system attained a reduction of 38-57% in BOD load from the wastewater. This result is in agreement with that of Logsdon et al. (2002), who stated that a noticeable reduction in pollutant loads is achieved when slow sand filter is used in small water system treatment. The SSF system showed a ranging reduction efficiency values of 26-46% in COD pollution load across all treatment batches. ...
Article
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Indiscriminate disposal of untreated cassava wastewater is a major environmental challenge faced by communities hosting indigenous cassava processors in Nigeria. This study is therefore aimed at assessing the effectiveness of a simple slow sand filtration system embedded with activated carbon layer for cassava wastewater treatment. The filters were loaded in layers with graded sand, gravel, and varying thickness of activated carbon bed. Cassava wastewater was obtained from a processing site at Ibogun, Ogun State, Nigeria. The filters were filled and left for about two weeks for "schmutzdecke" to form on the top surface of the sand bed and then operated at room temperature (28-34 °C) at hydraulic retention times of 6, 12, and 24 h. The result showed that collected wastewater had a mean value of 1357 NTU, 385, 31.87, and 716 mg/L of turbidity, biochemical oxygen demand (BOD), hydrogen cyanide (HCN) content, and chemical oxygen demand (COD), respectively. These values were above the permissible limit set by the local and international regulatory agencies. The filters with activated carbon showed a drastic reduction in the pollutants load (BOD: 38%-57%, COD: 26%-46%, HCN: 79%, and NTU: 96.5%-98%). This is corroborated by P-values <0.05 of 2.84 x 10-32 and 1.69 x 10-29 for COD and BOD, respectively. The obtained result also disclosed that some parameters did not conform to the acceptable limit but there was a reduction in key pollutants of cassava wastewater. Therefore, the filter can be used as a low-cost treatment mechanism for cassava wastewater prior to disposal.
... Repeated exposure of filter biofilms to MCs could favor growth and colonization of bacteria capable of degrading MCs, resulting in increased rates of biodegradation. Slow sand filtration is still commonplace in small water treatment systems with part-time operators (Logsdon et al., 2002) and could be useful in areas requiring less energy or a smaller footprint. One consideration is that filtered cyanobacteria cells could senesce and lyse, releasing MCs into the filtrate if not degraded within the filter (Svrcek and Smith, 2004); therefore, low-energy polishing steps (e.g., fixed-film solar photocatalysis) may also be necessary for dissolved MCs. ...
Article
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Microcystin (MC) production by cyanobacteria (i.e., blue-green algae) in freshwater resources has resulted in significant financial losses and adverse effects on the health of humans, pets, fish, wildlife, livestock, and plants. As harmful blooms of cyanobacteria (often referred to as harmful algal blooms, or "HABs") increase in frequency, intensity, and severity in freshwater systems throughout the United States and globally, the management decision of "no action" (or a decision not to intervene) results in loss of the beneficial services provided directly and indirectly by the water resource, and increases the likelihood that people and other organisms will be exposed to MCs. Peer-reviewed data and other useful information are readily available regarding characteristics of microcystins, effects on human health, ecological risks, and management approaches for MC-producing cyanobacteria and MCs. However, these data are rarely in a form that can be readily used to make scientifically defensible decisions. The goal of this paper was to provide a review of the literature related to risk management of MCs and to organize this information in a logical manner to provide a decision support document for water resource managers, regulators, and stakeholders.
... These results are in agreement with previous published articles. Logsdon et al. [30] and Visscher et al. [31] reported that slow sand filters were able to physically, biologically and chemically treat water. However, the slow sand filter was not capable of reducing the filtered WWW pH value. ...
Article
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The management of waste wash-water (WWW) is one of the most significant environmental problems associated with ready-mix concrete production worldwide. The problems are exacerbated should it be disposed of in an inappropriate manner. This study evaluated the potential of WWW recycling in ready mix concrete plants in Jordan. A representative waste wash-water sample (400 L) was collected from a basin in a ready-mix concrete company. A pilot plant on the lab scale was fabricated and installed. The treatment system consisted of a concrete washout reclaimer, wedgebed slurry settling pond, slow sand filtration unit, and a neutralization unit. Water samples were collected from all stages of the pilot plant and analyzed. The collected waste wash-water samples were utilized for replacement of well water (mixing water) at various ratios. Fourteen concrete mixtures were produced and cast, as well as tested at various curing ages (7, 28, and 90 days). The results show that the raw WWW was not acceptable as mixing water even after dilution as it led to significant reductions in concrete compressive strength and low workability. However, the WWW from the settling pond, the filtered WWW and the filtered-neutralized WWW at dilution ratios up to 75% were shown to be potential alternatives to fresh water for ready-mixed concrete. Therefore, the current guidelines for mixing water quality should be revised to encourage the reuse of the WWW.
... Water is one of the most important resources which human being has exploited than any other resources for sustenance of their life. Rising demands for water to supply of agriculture, industry and cities are leading to competition over the allocation of limited fresh water resources Logsdon G., [1]. The world's supply of fresh water is finite and is threatened by pollution. ...
... Municipal wastewater treatment is also based on the floc, which are fragile structures in activated sludge plants. Floc is a type of biofilm formed on the surface of sand to remove organic compounds and metals from treatment systems or natural reservoirs (Logsdon et al., 2002). Biosorption (microbial or plant cell) and biotransformation (enzymes or metabolites) are probably the most widely explored biological metal and organic hazardous pollutants removal strategies. ...
... Slow sand filtration (SSF) is considered the oldest and effective method of water purification but little scientific research have been done into its theoretical and application [1] This technology is effective in removal of turbidity, heavy metals, and microorganism such as protozoa, viruses and bacteria [2,3,4]. This method performs high ability and reliability to bear up fluctuations in water quality, no need for chemicals application, easy to install in rural, semi-urban and remote areas, simple in design and operation [5] that suitable for certain purpose or area. ...
Article
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Four identically designed and constructed Capillary-Gravitational Slow Sand Filter (SSF) with different in its overflow media height were parallelly operated to filtered tofu liquid waste for the purpose to identify responses of debit and quality of permeate with the change of overflow media height. The experiment was conducted following 4x4 LS with the overflow media height as the treatment. Besides the debit for clear and polluted water, samples of the liquid waste and the permeate were taken and analysed for TSS, Turbidity, pH, BOD and COD. Result of analysis showed that debit of SSF was 182.6 -252.1 ml/minute for clear water; 81.3 – 153.5 ml/minute for tofu liquid waste; TSS 7.5 – 20.5 mg/L; Turbidity 0.58 – 3.84 NTU; pH 6.8 – 7.2; BOD 1.7 – 35.4 mg/L; COD 3.8 – 108.0 mg/L with removal efficiency more 96% when overflow media 4 cm or more. In conclusion, the SSF Grapilar reduced when it was used to filter polluted water. In terms of pollutant removal, SSF Grapilar was effective; it was able to remove more than 95% of TSS, Turbidity, BOD, COD and neutralized permeate of tofu liquid waste when the overflow media height was 4 cm or more.
... In fact, slow sand filtration is a water treatment process that is well suited for use by small water systems; the nature of the slow sand filtration causes some serious limitations on utilization of the process. An important limitation is the need for high-quality source water or appropriate pretreatment or filter modification to cope with water quality that is less than ideal (Logsdon et al. 2002). ...
Article
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In order to use purified wastewater on watering green spaces of Agadir city, we conducted this study to assess the bacteriological and physicochemical quality of treated wastewater in Mzar treatment plant. To realize these objectives, we analyzed four types of waters: raw water (RW), decanted water, purified water and purified water treated by the ultraviolet radiation (PWUV). The biologically analyzed parameters are fecal coliforms (FC) and fecal enterococci (FE). The physicochemical parameters are: pH, electrical conductivity, chemical oxygen demand (COD), five-day biological oxygen demand (BOD5) and total suspended solids (TSS). The results showed a high level of bacterial contamination in all types of waters, and the average loads of FC were between 4.71 × 10⁶ CFU/100 mL (RW) and 1.45 × 10³ CFU/100 mL (PWUV), while loads of FE were between 2.62 × 10⁵ CFU/100 mL (RW) and 7.92 CFU/100 mL (PWUV). The physicochemical parameters show a pH close to neutrality and a high electrical conductivity (3261 μS/cm) in PWUV. In all stages of wastewater treatment, values of COD, BOD5 and TSS were under the limit values recommended by Moroccan standards. Except for the electrical conductivity and FC, all the studied parameters were under the limit values requested by the Moroccan standards. The microbiological quality of PWUV is unstable, and if these waters are reused, they can affect the microbiological and physicochemical quality of green spaces and groundwater.
... The process is passive and the filter's effectiveness is dependent mostly upon the development of a biofilm attached to the sand grains and the schmutzdecke, a biologically active mat that develops on the filter surface. Inclusion of a layer of granular-activated carbon in a slow sand filter bed has improved capability for control of synthetic organic chemicals (Logsdon et al., 2002). Granular organic carbon may also be used with slow sand to treat a portion of the dissolved organics or colour. ...
Article
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Most waterborne diseases can be prevented using simple, low cost water filtration techniques. The aim of this study is to design a low cost domestic slow sand filter, which can be operated and maintained effectiveness at household level by a member of the family, and determine its effectiveness in removing selected contaminants from the raw groundwater. Fine sand, activated charcoal, coarse sand, and gravel were used as media column for the developed slow sand filtration media. Common selected physico-chemical and microbial water parameters were examined before and after filtration with the slow sand filtration system. The filter was able to remove turbidity of the raw groundwater in the range of 86-92% without hampering the pH value or the temperature below the acceptable standards set by the Nigerian standards for drinking water quality. The filter media was able to reduce an average of 44-82%, 29-53% and 60-66% of total hardness, calcium hardness and chloride content, respectively from the chemical composition of the groundwater samples. The media also showed high effectiveness in reducing biological impurities from the groundwater. It was able to remove effectively the concentration of E-Coli and coliform counts. The average percent removal of E-coli and coliforms was found to be 100%. These were achieved with the aid of the bio-film layer that developed on the topmost part (fine sand layer) of the filter which was able to predate on the microbes in the groundwater samples. Slow sand filters are a sustainable means of water treatment when applied to appropriate source waters and when designed and operated properly.
... SSF are one of the oldest water treatment technologies (Huisman and Wood, 1974;Logsdon et al., 2002). They are operated continuously without backwashing, albeit at much lower hydraulic loads than bioRSF, leading to empty bed contact times of 3e12 h (Haig et al., 2011). ...
Article
Control of the organic substrate pool that determines the microbial growth potential (MGP) of feedwater in seawater reverse osmosis (SWRO) is a challenge unresolved in conventional or advanced membrane pretreatment. Slow sand filtration (SSF) combines filtration with biodegradation, but its capability of reducing MGP, proteins and carbohydrates on seawater feeds is not known. Two SSF, one constructed with new media (newSSF) and one from a previous filtration run (oldSSF), reduced MGP as measured in a growth assay with the marine organism Pseudoalteromonas songiae by one order of magnitude after maturation periods of 76 and 61 days, respectively. The reduction of the amount of biopolymers deposited on the surfaces of SWRO membranes in laminar fluid flow cells was significant with filtrates from biologically non-acclimated SSF (proteins: 60% (oldSSF) and −66% (new SSF), carbohydrates: 75% (oldSSF) and −70% (newSSF)) and an even greater reduction was observed after filter maturation (proteins: 81% (oldSSF) and −76% (new SSF), carbohydrates: 88% (oldSSF) and −88% (newSSF). Turbidity was less than 0.3 nephelometric turbidity units (NTU) and silt density index (SDI) < 4 immediately after startup and during the 181 days operating period regardless of the oscillations of the raw sea water quality. Filtration and biological activity were restricted to the top 30 cm of the media column, with no significant further contribution of the deeper media layers to filtrate quality.
... Deste modo, a filtração lenta torna-se interessante para essa situação por ser de fácil operação, pois necessita apenas de cloração final para desinfecção da água. (BRASIL, 2011;LOGSDON, G. et al., 2002) Pesquisas apontam que, apenas com a utilização de tratamentos de água a nível familiar, comunidades que não possuem acesso ao sistema público de abastecimento podem reduzir significativamente o risco da incidência de diarreia. (CLASEN et al., 2006;FEWTRELL et al., 2005). ...
Experiment Findings
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Slow sand filters are considered by many authors a great alternative to the drinking water supply in rural and / or isolated areas where raw water that is treatable with this technique is available. Those filters operate at filtration rates of 3-12 m³/m²d, 20 to 50 times smaller than the rapid sand filters. Some studies use backwashing as an alternative for cleaning the slow sand filter with the goal of applying the technology in small communities, since filters that supply water to a small number of people don't require much space. In this study it was evaluated the influence of the effective diameter in water quality in the filters. Most filters had an average turbidity of less than 1.0 NTU, turbidity required at the output of the filters by decree No. 2914/11 of the Brazilian Ministry of Health. In the study, smaller diameter filter beds had effectively filtered water of better quality, and effective production. _______________ Filtros lentos são considerados por diversos autores uma excelente alternativa para o fornecimento de água potável em comunidades rurais e/ou isoladas, quando se dispõe de um manancial passível de tratamento com esta técnica. Esta tecnologia opera com taxa de filtração de 3 a 12 m³/m².dia, 20 a 50 vezes menores que os filtros rápidos. Alguns trabalhos utilizam a retrolavagem como forma alternativa de limpeza de filtro lento com área superficial reduzida com o objetivo de aplicar a tecnologia em pequenas comunidades, uma vez que cada filtro abastece um número pequeno de pessoas. Neste trabalho foi avaliada a influência do diâmetro efetivo na qualidade de água nos filtros avaliados. A maioria dos filtros apresentaram em média turbidez menor que 1,0 uT, exigido na saída dos filtros pela portaria nº2914/11 do Ministério da Saúde. No estudo, os filtros de menor diâmetro efetivo apresentaram a melhor qualidade na água filtrada, assim como maior produção efetiva.
... Slow sand filtration is a simple technology that can be used to reduce the pollutant load of wastewater to the standards for irrigation. 8,9 However, little work has been done on the application of Slow Sand Filters (SSFs) in wastewater quality improvement . 10 The process is passive and the effectiveness of the filters is dependent upon the development of a biofilm attached to sand grains. ...
Article
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Water scarcity has resulted to urban residence to resort to using untreated wastewater to irrigate their crops. This practice raises concerns on health of the farmers and consumers of the crops. The study aimed at determining whether the effluent from Boundary Sewage Treatment Plant was up to national and international standards recommended for irrigation, if not they were further subjected to slow sand filtration of different sand sizes (0.1 and 0.05 mm ) to polish the effluent. Pour plate method was used to determine total coliforms (TC), BOD5 technique for Biological oxygen demand (BOD), COD digestion for chemical oxygen demand (COD), gravimetric method for total dissolved solids (TDS) and total Suspended solids (TSS). One sample t- test during dry season showed that BOD, COD, TC and TSS in the effluent were significantly higher (p0.05) than the compared standards for the wastewater to be used for crop irrigation. The filters improved the effluent from the treatment plant to the standards for irrigation. The sequential treatment of the raw wastewater by the Boundary Sewage Treatment Plant and the slow sand filtration technique made the wastewater to achieve the standards it can be utilized for crop irrigation
... Historically and up to the present day, microbial processes have been used in the production of potable water. Biological drinking water treatment has been widespread since the 1800s in the form of slow sand filtration or bank filtration (Schubert, 2002;Logsdon et al., 2011). While historically, biological water treatment was empirical, we now have the technology and tools to understand the structure and function of the microbial communities involved in biological water treatment, potentially enabling control and optimization, making these processes even more attractive. ...
Article
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Sustainable Development Goal 6 requires the provision of safe drinking water to the world. We propose that increased exploitation of biological processes is fundamental to achieving this goal due to their low economic and energetic costs. Biological processes exist for the removal of most common contaminants, and biofiltration processes can establish a biologically stable product that retains high quality in distribution networks, minimizing opportunities for pathogen invasion.
... It removes coliform bacteria, algae, color, and iron and manganese content of water [3,5]. Sand filters work using a complex biological film that grows naturally on the surface of the sand which merely functions as a substrate for the filtration. ...
Article
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Objective: This study was conducted to design a portable antimicrobial water filter which is both economic and easy to use.Methods: A prototype following the designing of the water filter was constructed. Layers of sand, cloth, activated charcoal, and cotton containing compartments were built for carrying out water analysis.Results: Most probable number index of Vellore Institute of Technology lake water was compared with that of filtered water. Complete water analysis was done, and the sand filter layer was observed to be responsible for a maximum of the antimicrobial action of the filter.Conclusion: The study demonstrated that the proposed design of water filter is efficient in removal of turbidity, odor, and microbial content of lake water along with decreasing the acidity of water.
... The performance of the self-prepared AC was better than that of the high-tech AC made from coconut shell and rice husk, in which COD reductions of 46% to 71% and 45% to 73% were obtained, respectively (Mohan et al., 2008). Further reduction after filtration is consistent with previous findings, in which a 75% to 100% COD reduction was reported when sand filtration was used (Palmateer et al., 1999;Amy et al., 2006;CAWST, 2009;Logsdon et al., 2002). Thus, in terms of COD concentration, the effluent from the CACS system has met the drinking water standard. ...
Article
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Drinking water is supplied through the centralized water supply system and may not be accessed to communities in rural areas of Malaysia. This study investigated the performance of a low-cost, self-prepared combined activated carbon and sand filtration (CACS) system for roof-harvested rainwater and lake water for potable use. Activated carbon was self-prepared using locally sourced coconut shell and was activated using commonly available salt rather than high-tech procedure that requires chemical reagent. The filtration chamber was comprised of local, readily available sand. The experiments were conducted with varying antecedent dry intervals (ADIs) of up to 15 days and lake water with varying initial COD concentration. The CACS system managed to produce effluents, complying with the drinking water standards for the parameters pH, BOD5, COD, TSS, and NH3-N. The CACS system successfully decreased the population number of Escherichia coli (E. coli) in the influents to a population of less than 30 CFU/100 mL. Samples with a higher population of E. coli (that is more than 30 CFU/100 mL) did not show 100% removal. The system also showed high potential as an alternative for treated drinking water for roof-harvested rainwater and class II lake water.
Preprint
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Elevated/altered levels of dissolved organic matter (DOM) in water can be challenging to treat after wildfire. Biologically-mediated treatment removes some DOM; its ability to remove elevated/altered post-fire dissolved organic carbon (DOC) resulting from wildfire ash was investigated for the first time. Treatment of wildfire ash-amended (low, moderate, high) source waters by bench-scale biofilters was evaluated in duplicate. Turbidity and DOC were typically well-removed (effluent turbidity ≤ 0.3 NTU; average DOC removal ~20%) in all biofilters during periods of stable source water quality. Daily DOC removal across all biofilters (ash-amended and controls) was generally consistent, suggesting that (i) the biofilter DOC biodegradation capacity was not deleteriously impacted by the ash and (ii) the biofilters buffered the ash-associated increases in water extractable organic matter. DOM fractionation indicates this was because the biodegradable low molecular weight neutral fractions of DOM which increased with ash addition were reduced by biofiltration, while humic substances were largely recalcitrant. Thus, biological filtration was resilient to wildfire ash-associated DOM threats to drinking water treatment, but operational resilience may be compromised if the balance between readily removed and recalcitrant fractions of DOM change, as was observed during brief periods herein.
Chapter
Biofilms are an aggregate of microbes enclosed within extra polysaccharides. These microbes attach themselves to the substrate via polymers, protein, and DNA complexes. Biofilm provides microbes with a unique environment that protects them from environmental hazards. Biofilms formed by single species are predominant but the consortium biofilms have a better ability to combat remediation because of the ability of division of labor mechanism of each individual species. Biofilms in nature exist in rivers, lakes, and all the water bodies. These biofilms follow the process of attachment to the substrate, formation of monolayer and slime production and colonization utilizing multilayer cells, further, the mature biofilms detach from the slime layer. Pollution in water bodies is growing at an alarming rate and this creates ecological stress in water bodies. Water pollution occurs when an unwanted substance contaminates the environment. The main agents (causative) that are responsible for contamination in the water bodies are usually heavy metals, limiting or excessive nutrient availability, pesticides, pharmaceuticals and thereby leading to changes in water properties. The main conventional treatment process includes physical, chemical, and biological treatments to combat contamination in water bodies. Physical treatments include processes such as screening, sedimentation, and filtration whereas chemical treatment includes coagulation, precipitation and disinfection, and biological treatment that involve the dissolved and suspended organic matter. Biofilms provide possible remediation by absorption, immobilization, and degradation of organic matter. Biofilms are providing better insights to combat remediation. In the present chapter, we will focus on conventional methods of treatment, the basics of biofilms, and their mechanism to curb contamination in water bodies.
Article
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In this study, the effect of electric fields applied to a quartz sand bed on electrokinetics and the disinfection performance of an E-slow sand filter (reduction of Escherichia coli) were investigated. Results of electrokinetic experiments have shown that coliforms are electroosmotically transported to the cathode with a velocity of 0.6 cm h À1 (E ¼ 4 V cm À1). In the absence of an electric field and at electric field strengths of ,4 V cm À1 , a diffuse random movement to the cathode and the anode was the only translocation mechanism. Hence, the electroosmotic transport may represent an additional component of motion during E-slow sand filtration influencing its disinfection performance. Based on this, comparative experimental investigations on the disinfection performance of a slow sand filter without and combined with an electric field were carried out. In the absence of an electric field, the adsorptive filter effect of quartz sand contributes to an initial bacterial retention by 0.8 log levels. Applying an electric field strength of 4 V cm À1 caused an increase of E. coli reduction up to 4 log levels. The electrokinetically enhanced accumulation of E. coli in the filter bed is assumed to be the major effect mechanism in the E-slow sand filter.
Chapter
New challenges have arisen as a result of the advancement of technology and the global demand for various commodities. Various types of pollution are posing a serious threat to the environment and to human health. These pollutants need to be removed from the environment but in an eco‐friendly way. Bioremediation is an environmentally friendly method for detoxifying contaminated environs. Bioremediation is advantageous when compared with other strategies because it causes no habitat disturbance in the area being treated. Biofilms are a microbial community that forms on the surface of a substrate and is normally bounded by an extracellular polymeric substance. Microbes are classified as planktonic cells in nutritionally rich culture media based on their morphological, physiological and development characteristics since the emergence of microbiology. Use of biofilms in various contaminated environs have shown promising results and that is the reason that this technique is gaining attention and importance day by day. Biofilms are an eco‐friendly and sustainable option for remediation of polluted environs
Chapter
Water scarcity is a global issue. This problem, coupled with drying up of rivers and wells during the dry season, impacts on food security, making it impossible to grow crops throughout the year. As a result, there is increased demand of the already scarce resource. Additionally, the high cost of conventional treatment of water leaves most people in the periurban and rural communities with no alternative but to resort to readily available sources that are normally of low quality exposing them to waterborne diseases. This informal practice raises concerns on health issues to the consumers and farmers of the crops. Some of the conventional technologies commonly used are too expensive, too complex, or incompatible with local customs and beliefs. Thus, there is need for effective yet affordable methods of water treatment that are acceptable. Sand filtration is a simple purification process that combines biological and physical mechanisms to reduce the pollutants. Being one of the earliest forms of water treatment and an efficient process of particles and pathogens removal, it is suitable for developing communities due to the simple design, basic maintenance procedures, and low labor costs. The performance of sand filters depends on sand grain sizes, flow rate, retention time, and sand bed depth as the main parameters. This chapter will discuss the individual use of sand filters and in combination with other technologies to improve water quality in communities in developing countries.
Chapter
The rapidly increasing industrialization has adversely affected the environment due to deterioration of water and air quality. The continuous addition of hazardous chemicals, gaseous contaminants, and particulate materials to our environment imposed the life-threatening challenges for flora and fauna. There is an urgent need to adopt the sustainable technologies to reduce the contamination occurring in air and water resources. To cope up with various types of contaminants abatement techniques have been employed. In the recent decade the biofiltration-based methods have been emerged as promising abatement techniques to remove the hazardous contaminants from wastewater or polluted air. The biofiltration exploits the potentials of microbial systems (bacteria and fungi) to degrade the wide range of chemicals and volatile organic components (VOCs). In this chapter emphasis has been given on the basic concepts and mechanism of biofiltration along with its application for treatment of wastewater and polluted air. The details about the removals of hazardous heavy metals, cationic-anionic dyes, xenobiotics, organic contaminants, and assimilable organic carbon from water has been discussed. The removal of VOC, malodorous compounds, and sulfurous compound from air have been discussed. The chapter also gives the light about pros and cons of biofiltration.
Chapter
Water is a prerequisite for live and living. Presently, there is a huge water crisis throughout the world due to rapid urbanization, speedy expansion of metropolises and environmental pollutions. Filtration is one of the most key components of successful treatment processes of water and wastewater. Biofiltration is one of the filtration processes that use biomass on the filter media to remove unwanted substances from the water and wastewater. Hence, improved applications of biofiltration in water and wastewater treatment can be observed as green or sustainable engineering technology. Conventional water treatment systems experience difficulty in removing organics matter and pollutants. Biofiltration has the ability to eliminate both suspended and dissolved organic matter prior to disinfection. The application of biofiltration is growing day by day in the field of wastewater treatment. Therefore, this book chapter focuses on the deliberation on various biofiltration processes, advancement in biofiltration and design considerations of an adequate biofilter for wastewater treatment. In the current scenario, a large scale water treatment system is incapable of fulfilling the vast demand of pollutant-free potable water. The viability and sustainability of water resources and their effective and efficient utilization are also challenging and required huge attention. This book chapter targets to review the diverse mechanisms by which biofilter can purify the water pollutants, the pilot-scale application of biofilter with conventional water purification system and their pivotal role in sustainable wastewater treatment.
Conference Paper
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Um filtro lento com limpeza automática (retrolavagem) foi instalado em uma escola de ensino infantil e primária para o fornecimento de água potável. Filtros lentos são tecnologias simples de tratamento de água e a retrolavagem automatizada facilita a manutenção do sistema pelos utilizadores da tecnologia. A escola Leandro dos Santos em Ituporanga, Santa Catarina, foi escolhida para a implantação do filtro por receber água da rede sem nenhum tipo de tratamento, após captação por meio de sistemas Caxambu. Um filtro foi instalado em parceria entre a comunidade, os pesquisadores e o fabricante do sistema, com capacidade para produzir até 3840 L/d, suficiente para utilização nas instalações. Também foi instalado um sistema para cloração da água filtrada. Após a instalação do filtro e o clorador, o sistema passou a ser operado pelos funcionários da escola que também monitoram a dosagem de cloro. O custo total foi de aproximadamente R$22600,00, que foi considerado elevado, por isso é recomendado a locais com capacidade de investimento onde a qualidade de água é necessária, como estabelecimentos públicos ou agroindústrias familiares.
Article
Slow sand filtration is a common technology providing potable water in rural households across Latin America, Asia and Africa. Two PVC household slow sand filters (HSSF) were operated in continuous (C-HSSF) and intermittent (I-HSSF) flow modes for eight consecutive months. A non-woven blanket was installed on the fine sand top to facilitate cleaning with scheduled maintenance undertaken every 30 days. The efficiency of each HSSF was evaluated via physico-chemical indicators (reduction of turbidity and colour) with biological performance assessed via total coliform and E. coli enumeration post treatment. There were no statistically significant differences between the continuous flow and intermittent flow models for physical-chemical and total coliform reduction parameters. However, when evaluating E. coli, C-HSSF performed better (p = 0.02). The non-woven blanket was subjected to weekly analysis using a Clark-type amperometric microsensor (diameter < 20 µm), which measured dissolved oxygen (DO) concentration in the adherent biofilm. DO microprofiles illustrated a variation in biofilm growth, which were associated with a progressive increase in the HSSF efficiency. The maximum DO depletion value measured during several months of operation showed no significant difference between I-HSSF and C-HSSF (p=0.98). The microsensor measurements provided unprecedented results in real time. These results can help to understand the efficiency of the filter in relation to the biofilm growth, the dissolved oxygen depletion and turbidity removal.
Chapter
Arsenic (As), one of the highest harmful pollutants found in drinking/groundwater, is owing to have unfavourable impacts, for example, skin disease, on human health. The new Environmental Protection Agency (EPA) assigned the maximum contaminations of arsenic in groundwater is 10μg/L, and several drinking water plants are needing extra treatment to accomplish this standard. In recent years, several researchers have been attempting to discover practical and expendable adsorbents for some water filtration systems that are utilized in many arsenic endemic territories. Metal oxide-based adsorbents had been proved to be the best strategies for arsenic expulsion/removal. This chapter reviews the removal of both arsenite (As III) and arsenate (As V) species from drinking/groundwater. Also, we give an overview of traditionally applied strategies to expel both arsenic species to incorporate coagulation-flocculation, oxidation, and membrane techniques. More focus has been given to adsorption methods, type of adsorption and factors affecting adsorption. Moreover, brief summary has been given for an advancement on the efficacy of different nanomaterials and composites for the polluted water treatment. A basic examination of the most generally explored nanomaterials is highlighted.
Article
With the increased use of wastewater for irrigation, there is the need to reduce the contaminant levels in wastewater. The slow sand filtration (SSF) is one such method that can be used to improve wastewater quality. However, the treatment quality depends among other factors on the depth of sand bed and the effective size. Acquiring sand of a particular effective size is becoming increasing difficulty and, therefore, this study sought to investigate over a specified area, the optimal depth and effective size that will be able to get rid of contaminants in wastewater. In separate experiments, three depths (30 cm, 40 cm and 50 cm) and two effective sizes (0.27 mm and 0.45 mm) were set up to investigate their effectiveness in removing Faecal coliform, E. coli and heavy metals (Pb, Cu and Fe) for wastewater from a peri-urban drain used for irrigating vegetables. Results showed that a minimum sand bed thickness of 40 cm and an effective size of up to 0.45 mm reduced the contaminants tested significantly, wastewater from the drain can be treated. It must be mentioned that the finer sand (0.27 mm) had a slightly better removal efficiency. This implies that the extra cost of acquiring sand of relatively smaller effective size and a higher bed depth with the aim of improving wastewater quality can be saved. Further investigations are being carried out on the combined effects of the optimal sand bed depth and effective size.
Article
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The ambitious UN Sustainable Development Goal for 2030 to 'leave no one 21 behind' concerning safe drinking water calls for the development of universally 22 applicable and affordable decentralized treatment systems to provide safe drinking 23 water. Published results suggest that well-designed biological sand filters (BSFs) 24 amended with metallic iron (Fe 0-BSFs) have the potential to achieve this goal. Fe 0-BSFs 25 quantitatively remove pathogens and a myriad of chemical pollutants. Available data 26 were achieved under various operating conditions. A comparison of independent 27 research results is almost impossible, especially because the used Fe 0 materials are not 28 characterized for their intrinsic reactivity. This communication summarizes the state-of-29 the-art knowledge on designing Fe 0-BSFs for households and small communities. The 30 results show that significant research progress has been made on Fe 0-BSFs. However, 31 well-designed laboratory and field experiments are required to improve the available 32 knowledge in order to develop the next generation of adaptable and scalable designs of 33 Fe 0-BSFs in only two years. Tools to alleviate permeability loss, preferential flow and the 34 use of exhausted filters are presented. 35
Article
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Slow sand filter processing is done by separating raw contaminant water which is passed slowly on sand. Fluctuating raw water quality resulted in the schmutzdecke layer not growing optimally. Therefore, it is needed media that help the performance of the sand filter. One of the media used is geotextile. The geotextile is useful as a medium to optimize the growth of microorganisms in the schmutzdecke layer. Geotextiles have similar surface structures such as sand filters as well as their pores. The purpose of this study was to determine the effectiveness of adding geotextiles in reducing turbidity parameters, number of coli and COD. This study used slow sand filter reactor with a continuous flow system of 0.3 m3 / m2.jam for 7 days. Based on the research, the addition of geotextile media is quite effective and can improve the performance of slow sand filter. Percentage of turbidity removal reached 94.27%, coli 99.40% and COD 92.85%. COD values tend to be dynamic as raw water conditions. Geotextiles is quite helpful in growing a layer of schmutzdecke because the structure resembles sand so as to increase the number of bacteria bed filters.
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Water resources are an absolute necessity for the success of manned planetary expeditions. Advanced water recycling technologies abound, but a low-tech, unpowered, proven system should be considered in case of crucial system failure in a remote environment. In this investigation, slow sand filters were developed utilizing local materials and Martian simulant. They were tested at the Mars Desert Research Station, and compared to its hydroponic wetland filtration system. The tested sand filters evolved as schmutzdecke biological films formed as evidenced by decrease in hydraulic conductivity, improving effluent quality as indicated by reductions in turbidity and bacteria, through both physical and chemical filtration. Matrix-water chemical interaction was indicated by dissolution of carbonates from the filtrant; modifying pH and increasing total dissolved solids, alkalinity, and hardness. The slow sand filters proved more effective than the wetland system, yet the optimal solution was determined a combination of both strengths; wetland roughing pre-treatment and denitrification, and bacterial removal from the sand filter.
Article
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Slow sand filtration may be not only the cheapest and simplest treatment process to operate and maintain but also the most efficient under appropriate circumstances. Limitations of conventional slow sand filters include significant reductions in filter run lengths should raw water turbidity and algal content exceed relatively low levels, poor organic precursor removals, and relatively long filter cleaning downtimes and ripening periods. This review article summarizes and evaluates modifications to slow sand filters that may address these limitations without compromising the simplicity of the treatment process. El filtrado lento de arena puede no sólo ser el proceso de tratamiento más barato y sencillo para operar y mantener, sino que también puede ser el más eficiente bajo ciertas circunstancias. Los límites de los filtros lentos de arena convencionales incluyen las reducciones significativas en la durabilidad de los filtros cuando la turbidez del agua natural y el contenido de algas exceden niveles relativamente bajos, la pobre remoción de los precursores orgánicos, y períodos relativamente largos de limpieza de filtros y períodos de maduración. Esta reseña resume y evalúa las modificaciones a filtros lentos de arena que pueden dirigirse estos límites sin comprometer la simplicidad del proceso.
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Three slow sand filter plants in northern Idaho were studied to evaluate their ability to produce good quality water and to control Giardia cysts, to determine the effects of design and operating factors on treatment performance, and to assess the effectiveness of monitoring and sanitary surveys. During the one-year study, the plants were sampled weekly for measurement of turbidity, total and fecal coliforms, and heterotrophic plate count. Samples were also analyzed for Giardia cysts and particulates. Results showed that if a slow sand filter is designed and operated according to accepted standards, it should provide consistent and effective water treatment, including a reduction in the concentration of Giardia cysts. Se estudiaron tres plantas de filtros lentos de arena en el norte de Idaho para evaluar su capacidad de producir agua de buena calidad y de controlar quistes de Giardia, para determinar los efectos del diseño y los factores de operación en el tratamiento, y para evaluar la efectividad de los estudios en cuanto al control y al aspecto sanitario. Durante el estudio que duró un año, las plantas fueron examinadas semanalmente para medir la turbidez, los coliformes totales y fecales, y el conteo heterotrofico en placas. Se analizaron muestras en lo relativo a quistes de Giardia y partículas. Los resultados demuestran que si se diseña un filtro lento de arena y se opera siguiendo las normas aceptadas, debería dar un tratamiento consistente y efectivo de aguas, incluyendo la reducción en la concentratión de quistes de Giardia.
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Biological activity within the sand bed had the strongest influence on removal efficiency of total coliform bacteria by slow sand filtration, as determined by six pilot filters (shown above). Temperature, sand bed depth, and sand size also had strong influence. La actividad biológica dentro de la cama de arena ejerce la influencia más grande en la eficiencia de la extracción total de bacterias coliformes por medio del filtración lenta por arena, conforme lo determinado con filtro experimentales de 0,3 m (1 pie) de diámetro. La temperatura, la profundidad de la cama de arena, y el tamaño de la arena también ejercían una fuerte influencia.
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Report on laboratory studies of two systems for algae removal from stabilization ponds covers submerged rock filter and upflow fly ash filter. The methods have been developed for the small communities with their limited resources in mind. Both investigations were conducted with effluent from the oxidation ponds serving Linwood, Kansas (sewered population 350). These ponds are divided into two equal size cells operating in series. They have a total surface area of approximately 2. 78 acres when operated at a liquid depth of 5 ft. Literature review is presented on analytical methods used in previous investigations.
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The ability of slow sand filters to remove enteroviruses from contaminated reservoir water has been assessed using experimental filters and attenuated poliovirus type 1. The effects of flow rate, depth of sand, temperature, filter maturity and cleaning on this process have been examined. The filters were found to be highly effective in removing viruses at up to 2.5 times the normal flow rate of 4.8 m per day and at temperatures as low as 5°C. The removal of bacteriophage T7 and naturally occuring bacteria by filtration have also been studied. When compared with poliovirus bacteria were less and bacteriophages were more efficiently removed.
Article
Riverbank filtration (RBF) is a process In hili pumping wells located along riverbanks induce a portion of the river water to flow toward the wells. During RBF, which has many similarities to slow-sand filtration, river water contaminants are attenuated from a combination of processes such as filtration, microbial degradation, sorption to sediments and aquifer sand, and dilution with background groundwater. RBF systems have been operating in Europe since the 1870s. In the United States, there has been renewed interest among large- to medium-sized utilities to use It as a mechanism of water production to reduce treatment costs and to meet regulations on pathogens, disinfection by-products, and other contaminants under the Surface Water Treatment Rule. Although filtrate water quality from RBF systems can vary based on river conditions, it is possible that appropriately designed systems; can serve as pretreatment for drinking water, and at the same time, the utility can receive log-removal credits for pathogens and particle,. In addition, RBF can be used as a pretreatment for membrane filtration. In the United States, a knowledge gap exists oil the benefits and limitations of using RBF. This article addresses those gaps, outlining the benefits and limitations of the process. It also illustrates that RBF can be a viable alternative to surface water at suitable sites.
Article
Riverbank filtration involves the process of bank filtering where river water is passed through river banks and proceeds to the groundwater table. Water utility treatment follows the passage of bank filtrate and infiltrate collected in underground wells. Infiltration is used where the quantity of water provided by bank filtration is very low or due to geological conditions bank filtration is impossible or sources of groundwater at river bank are highly contaminated. Local conditions determine the residence time of bank filtrate in underground which can vary from 5 to 100.
Article
Slow sand filtration was selected to meet the Surface Water Treatment Rule requirements for the community of Camptonville, Calif. The slow sand filtration facility uses precast concrete vaults, hauled by truck to the site and laid out in a linear arrangement to adjust to the contour of the steep hillside site. This alternative filtration process is credited by the California Department of Health Services with 2-log Giardia and 1-log virus reduction. A 3-log Giardia and 4-log virus removal can be achieved with disinfection. The facility began operation in December 1991 and has maintained a treated water turbidity 30 ntu. The process effectively removes high levels of iron and manganese from the community's backup groundwater supply. In addition, low construction and operating and maintenance costs have kept customers' costs down.
Article
Small water systems face immense difficulties in meeting the requirements of the Surface Water Treatment Rule. This article describes partnerships formed between the state regulatory agency, communities, and consulting engineers in Oregon to assist small communities in meeting these requirements. A case study is presented of a small community that successfully installed slow sand filtration, which has proved to be an effective and appropriate treatment technology. Also described are several associated demonstration projects undertaken by state water program staff to develop pilot fílter and design guidelines for use in future projects. En los Estados Unidos los pequeños sistemas de aguas enfrentan grandes dificultades en llenar los requisitos de la Regia de Tratamiento de Aguas Superficiales. Este artículo describe las sociedades creadas entre la agencia regulatoria estatal, las comunidades, y los ingenieros consultores en Oregon para ayudar a las pequeñas comunidades a llenar esos requisitos. Se presenta el caso típico de una comunidad pequeña que instaló exitosamente una filtración lenta de arena, que se comprobó ser una técnica efectiva y apropiada de tratamiento. También están descritos varios proyectos asociados de demostración hechos por los oficiales del programa de aguas estatal para desarrollar de guias y diseño filtros piloto para ser usadas en proyectos futuros.
Article
Alternatives to conventional water filtration plants, which use coagulation, flocculation, sedimentation, and rapid filtration, may be appropriate for some small utilities. One such alternative is slow-rate filtration. This article describes pilot-plant studies that were undertaken to evaluate slow-rate filtration for the removal of particulates, total coliforms, standard plate count bacteria, and organice (total organic carbon and trihalomethane formation potential). Two pilot-scale filtration systems were used: a slow sand filter, operated for 800 days, and a second slow sand filter operated in parallel with a slow-rate filter containing granular activated carbon, operated for 200 days. Results are presented for both systems. Alternativas a plantas de filtración convencionales que utilizan coagulación, floculación, sedimentación y filtración rápida pueden ser apropiadas para pequeñas empresas de servicio. Una de estas alternativas es la filtración de razón lenta. Este artículo describe estúdios de planta piloto que se Ilevaron a cabo para evaluar la filtración de razón lenta en cuanto a remoción de partículas, coliformes totales, bacterias de contaje de plato standard, y orgánicos (carbón orgánico total y formación potencial de trihalometanos). Dos sistemas de filtración en escala piloto fueron utilizados: un filtro lento de arena operado por 800 días y un segundo filtro lento de arena operado en paralelo con un filtro lento conteniendo carbón activado granular operado por 200 días. Se presentan resultados de ambos sistemas.
Article
The design experience at Empire, Colo., and the postdesign evaluation have provided knowledge about the efficiency of the slow sand filtration process at full-scale and the basis for recommendations concerning slow sand filtration practice. Operation of the filter required daily inspection plus measurement of water depth and effluent turbidity, along with monthly scraping. Scraping required only two workhours, however, and only 0.2 in. (0.5 cm) of surface was removed. The projected life of the sand bed at this rate of removal is 15 years, with a residual depth of 1 ft (0.3 m). Giardia cysts were found in the raw water on five occasions, but none were found in the finished water. Microscopic organisms and particles were found in the raw water but either zero or rare numbers were found in the finished water. La experiencia de diseño en Empire, Colo., y la evaluación postdiseño han proporcionado información sobre la eficiencia del proceso de filtración lenta en arena en gran escala y la base para recomendaciones concerniendo la práctica de filtración lenta en arena. El manejo del filtro requirió inspección diaria y medición de la profundidad del agua y turbidez del líquido efluente, además de raspado mensualmente. El raspado requiere solamente de dos horas de trabajo sin embargo, y solamente se removió 0.2 pulgadas (0.5 cm) de superficie. La vida proyectada del lecho de arena para filtración a esta velocidad de remoción es de 15 años, con una profundidad residual de un pie (0.3 m). Se encontraron quistes de Giardia en el agua cruda en cinco ocasiones, pero ninguno se encontró en el agua terminada. Organismos microscópicos y partículas se encontraron en la agua cruda, pero ninguno pocos se encontraron en el agua terminada.
Article
Pilot-plant studies were undertaken to determine the efficiency of slow-rate sand filters in removing Giardia cysts and other substances. The filters removed virtually 100 percent of the Giardia cysts, 96 percent of standard plate count bacteria, and 98 percent of particles. Because of the efficiency and the passive nature of slow-rate sand filtration, this technology is especially appropriate for small water systems. Estudios de planta piloto fueron llevados a cabo para determinar la eficiencia de filtros de arena de razón lenta en la remoción de quistes de Giardia y otras substancias. Los filtros removieron virtualmente un 100 por ciento de los quistes de Giardia, un 96 por ciento de bacterias de contaje de plato standard, y un 98 por ciento de partículas. Debido a la eficiencia y la naturaleza pasiva de la filtración de razón lenta por arena esta tecnología es especialmente apropiada para sistemas de agua pequeños.
Article
Full-scale municipal slow sand filters at seven sites in the Syracuse, N. Y., area were monitored before, during, and after filter scraping to verify the presence or absence of a ripening period, to determine the filter run length, and to quantify the labor and material required for scraping and resanding operations. Results showed some evidence of a ripening period, ranging from 6 h to 2 weeks, in four of the 10 operations monitored. The presence or absence of a ripening period did not seem to be related to the use of prechlorination, to water temperature, to scraping methodology, or to frequency of filter maintenance. The factor that seemed to have the most significant effect on the quality of the filtrate was the amount and nature of the particulate matter present in the raw water. En siete sitios en el área de Syracuse (N.Y.), se controlaron a nivel municipal los filtros de arena lentos antes, durante, y después de la limpieza por raspado de los mismos para comprobar la presencia o ausencia de un período de "maduración" y determinar el largo de la operación del filtro y cuantificar los materiales y mano de obra requeridos para las operaciones de raspado y reposición de la arena. Los resultados mostraron cierta evidencia de un período de "maduración" que iba desde 6 horas hasta 2 semanas en 4 de las 10 operaciones observadas. La presencia o ausencia del período de "maduración" no parecía estar relacionado con el uso de preclorinado, la temperatura del agua, el método de raspado, o la frecuencia en el mantenimiento de los filtros. El factor que pareció tener el efecto más significativo en la calidad del filtrado fue la naturaleza de la materia en partículas en el agua cruda.
Article
Because of their simplicity, efficiency, and economy, slow sand filters are appropriate means of water treatment for community water supply in developing countries and for small water systems in other areas of the world, including the United States. The basic elements of a slow sand filter are described, as are planning, design, and construction aspects, with special emphasis on maintenance. Some cost figures for systems in India and Colombia are included. Operational procedures for maintenance and resanding are set out. Debido a la simplicidad, eficiencia, y economia, los filtros lentos de arena son apropiados para el tratamiento de aguas en el suministro de agua a la comunidad en países del tercer mundo y en los sistemas pequeños de agua en otras partes del mundo, incluyendo los Estados Unidos. En este artículo se describen los elementos básicos de un filtro lento de arena, lo mismo que su planeamiento, diseno, y aspectos de construcción, con especial énfasis en el mantenimiento. Se incluyen cifras sobre costos en India y Colombia.
Water supply Technologies for up-grading existing or designing new drinking water treatment facil-ities Slow sand filtration: design, operation, and main-tenance
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Cable, C.J., and Jones, R.G. 1996. Assessing the effectiveness of ozonation followed by slow sand filtration in removing THM pre-cursor material from an upland raw water. In Advances in slow sand and alternative biological filtration. Edited by N. Graham and R. Collins. John Wiley & Sons, New York. pp. 29–37.
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Portfolio submitted for part fulfilment of the degree of Engineering Doctorate in Environmental Technology
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In Slow sand filtration: an international compilation of recent scientific and operational developments
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Evaluation of roughing filtration design variables. American Water Works Association Research Foundation
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Section 3.1. Overcoming water quality limitations with the multi-barrier concept: a case study from Columbia. In Slow sand filtration: an international compilation of recent scientific and operational developments
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Galvis, G., Visscher, J.T., and Lloyd, B.J. 1994. Section 3.1. Overcoming water quality limitations with the multi-barrier concept: a case study from Columbia. In Slow sand filtration: an international compilation of recent scientific and operational developments.American Water Works Association, Denver, Co. pp. 47-60.
GAC enhanced slow sand filtration (GAC Sandwich TM ). In Advances in slow sand and alternative biological filtration
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  • N V Goodman
  • A J Rachwal
Bauer, M.J., Colbourne, J.S., Foster, D.M., Goodman, N.V., and Rachwal, A.J. 1996. GAC enhanced slow sand filtration (GAC Sandwich TM ). In Advances in slow sand and alternative biological filtration. Edited by N. Graham and R. Collins. John Wiley & Sons, New York. pp. 223-232.
Multi-stage slow sand filtration for the treatment of high turbid water. In Advances in slow sand and alternative biological filtration
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Li, G.B., Ma, J., and Du, K.Y. 1996. Multi-stage slow sand filtration for the treatment of high turbid water. In Advances in slow sand and alternative biological filtration. Edited by N. Graham and R. Collins. John Wiley & Sons, New York. pp. 371–378.
Slow sand filter and package treatment plant evaluation: operating costs and removal of bacteria, Giardia, and trihalomethanes. USEPA/600/2-85/052
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Pyper, G.R. 1985. Slow sand filter and package treatment plant evaluation: operating costs and removal of bacteria, Giardia, and trihalomethanes. USEPA/600/2-85/052. U.S. Environmental Protection Agency, Cincinnati, Ohio.
The quest for pure water
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Baker, M.N. 1981. The quest for pure water. Vol. 1. 2nd ed. American Water Works Association, Denver, Co.
Slow sand filter design
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Pyper, G.R., and Logsdon, G.S. 1991. Slow sand filter design. In Slow sand filtration. Edited by G. Logsdon. American Society of Civil Engineers, Reston, Va. pp. 122-148.
Microbiology of water and sewage
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  • T R Lord
Gainey, P.L., and Lord, T.R. 1952. Microbiology of water and sewage. Prentice-Hall, Inc., Englewood Cliffs, N.J.
Assessing the effectiveness of ozonation followed by slow sand filtration in removing THM precursor material from an upland raw water
  • C J Cable
  • R G Jones
Cable, C.J., and Jones, R.G. 1996. Assessing the effectiveness of ozonation followed by slow sand filtration in removing THM precursor material from an upland raw water. In Advances in slow sand and alternative biological filtration. Edited by N. Graham and R. Collins. John Wiley & Sons, New York. pp. 29-37.
Field study of Giardia and Cryptosporidium removal from Pennsylvania surface waters by slow sand and diatomaceous earth filtration
  • M M Ghosh
  • P F Schuler
  • P Gopalan
Ghosh, M.M., Schuler, P.F., and Gopalan, P. 1989. Field study of Giardia and Cryptosporidium removal from Pennsylvania surface waters by slow sand and diatomaceous earth filtration. Environmental Resources Research Institute, Pennsylvania State University, University Park, Pa.
Removal of Cryptosporidium oocysts by water treatment processes
  • T Hall
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