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The household slow sand filter patented biosand filter (BSF) has been implemented in several developing countries to improve access to safe water. Evaluating the sustainability of various BSF implementations is essential. However, most evaluations neglect interlinkages among factors. This leads to unclear identification of leverage points to enhance BSF sustainability, resulting in limited utility to policymakers. To address this issue, the present study carried out a systematic literature review and used systems thinking to establish complex interlinkages among some factors affecting BSF sustainability. A total of 38 studies in 21 countries from the Americas, Africa, and Asia evaluated the BSF and 31 factors were found across the studies. The most influential factors were continued use, produced water quality, operations and maintenance (OM), and willingness to pay. Continued use was positively correlated to produced water quality and negatively related to the amount of water produced. OM was positively correlated with household hygiene practices and negatively correlated with education level. Willingness to pay was positively related to household income and education level. BSF's discontinued use was attributed to broken parts and improper maintenance. This paper identified the main leverage points that should be targeted during BSF implementation to improve its sustainability. This study helps identify specific factors and enables policymakers to understand their interrelationships, facilitating well-informed decisions before implementing a BSF.

The Bucket filter (BF) is a modification of the conventional BioSand filter (CBSF) meant to make it more adaptable for use in rural communities. Unfortunately, it has a low microbial efficiency compared to the CBSF. This paper explored the potential of integrating Moringa Oleifera with the bucket filter by creating a hybrid system that would work as efficiently as the CBSF but lower in cost and lighter in weight. Four filters, including BF, CBSF, Moringa High dose (125 mg/l) bucket filter (MUBFHigh) and Moringa Low dose (75 mg/l) bucket filter (MUBFLow) were set up. For 91 days, they were evaluated for turbidity, pH, organic matter and E. coli. Results indicate that the MUBFHigh system had an E. coli removal efficiency of 81–98%, which was comparable to the CBSF. MUBFHigh also yielded water that met the WHO guidelines for turbidity, organic matter and pH although the pH was slightly lower than the initial water. The MUBFHigh also weighed between 15 and 20 kg compared to 230 kg for the CBSF. The initial cost of the CBSF was more than double the cost of the MUBFHigh system. Although more work is needed to operationalize the filter, this study provides a baseline for future research.

Biosand filters (BSFs) are widely used in rural and urban areas where access to drinking water is limited or non-existent. This study applies computational fluid dynamics in the assessment of hydrodynamic characteristics considering changes in the design of two BSF models to make construction options available to communities, without losing hydrodynamic efficiency. The commercial code ANSYS-CFX 20.1 together with a central composite design of experiments methodology to simulate the flow was used under different combinations of porosities, permeabilities, pipe diameters, and filter diameters and heights. These parameters were combined statistically from Statistica 13.3. Our results have shown that combining greater filter depths with smaller pipe diameters has played a key role in the BSF best performance, and the CAWST V10 model has performed better than HydrAid, with lower velocities and longer hydraulic retention times. HIGHLIGHTS Stable mathematical models predict water flow patterns in biosand filters.; The CAWST V10 model promoted more favorable hydrodynamic conditions for microbiological treatment than HydrAid.; The performance in water treatment is obtained for different heights and diameters of filters, and different diameters of tubes.;

Household Water Treatment and Safe Storage (HWTS) are recommended to supply the demand for drinking water in communities without conventional water supply systems. However, there is a lack of long-term laboratory studies regarding such technologies. We evaluated the contributions of each step of a multi-barrier system with pretreatment (sedimentation and fabric filtration), filtration in Household Slow Sand Filters (HSSFs) and disinfection (sodium hypochlorite) treating surface water for more than 14 consecutive months. Removal of turbidity, colour, organic matter, coliform group bacteria and protozoa were evaluated. Two HSSF models were compared, one with a diffuser vessel (HSSF-d) and one with a gravity float equipped vessel (HSSF-f). Correlations between efficiency and operational parameters were assessed. Overall, the multi-barrier system removed more than 90% of turbidity and more than 3.5 log of Escherichia coli. HSSF removed up to 3.0 log of Giardia spp. and 2.4 log of Cryptosporidium spp. HSSF-f presented significantly higher removal rates for turbidity, apparent colour and E. coli. Disinfection resulted in water with E. coli concentration lower than 1 CFU 100mL−1, however it was not able to inactivate protozoa. The evaluated system was able to reduce microbiological risks from water and could indeed be an alternative to communities that depend on surface water as their main source of supply. Nevertheless, further studies are recommended to include a low-cost disinfectant for protozoa inactivation. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the efficiency of four household slow sand filter (HSSF) models for the removal of microorganisms from river water throughout the development of their biological layers (schmutzdecke). Two models were designed to be operated continuously (HSSF-CC and HSSF-CT) and two intermittently (HSSF-ID and HSSF-IF). Filters were fed daily with 48 L pre-treated river water (24 h sedimentation followed by filtration through a non-woven synthetic blanket). Water samples were quantified by coliform group bacteria and analysed by bright field microscopy to visualize the microorganisms. Total coliform reduction was between 1.42 ± 0.59 log and 2.96 ± 0.58 log, with continuous models showing a better performance (p-values < 0.004). Escherichia coli reduction varied from 1.49 ± 0.58 log to 2.09 ± 0.66 log and HSSF-IF, HSSF-CC and HSSF-CT presented a similar performance (p-values > 0.06), slightly better than the one presented by HSSF-ID (p-value=0.04). Microorganisms, such as algae, protozoa and helminths were detected by microscopy in raw water and pre-treated water. Algae were the most significant group in these samples, although they were not visualized by bright field microscopy in the filtered water. Results showed the potential of HSSF in microbiological risk reduction from river water, which increases the range of point-of-use water treatments in rural communities. However, additional studies of the HSSF biological layer must be performed. [ABSTRACT FROM AUTHOR]

Biosand filter merupakan alternatif teknologi pengolahan air limbah. Penelitian ini bertujuan untuk: 1) Menganalisis efisiensi biosand filter menggunakan variasi komposisi dan ketinggian media dan 2) Membandingkan variasi komposisi dan ketinggian media yang paling efektif selama pengolahan menggunakan biosand filter. Penelitian ini menggunakan dua reaktor yang masing-masing berdimensi (30 x 30 x 100) cm dengan adanya variasi komposisi dan ketinggian media. Susunan media yang digunakan pada kedua reaktor terdiri dari media kerikil:pasir kasar:pasir halus:karbon aktif. Reaktor 1 mempunyai ketinggian masing-masing adalah (10:10:30:10) cm untuk media kerikil:pasir kasar:pasir halus:karbon aktif. Reaktor 2 media kerikil:pasir kasar:pasir halus:karbon aktif dengan masing-masing ketinggian adalah (10:10:15:25) cm. Filter dioperasikan secara batch dengan memanfaatkan gaya gravitasi. Pengambilan sampel dilakukan selama 20 hari dimulai dari hari ke-0, 5, 10, 15, dan 20. Hasil penelitian menunjukkan bahwa efisiensi penurunan konsentrasi BOD dan TSS pada reaktor 1 dengan susunan media kerikil:pasir kasar:pasir halus:karbon aktif (10:10:30:10) cm berturut-turut adalah 62,92% dan 78,40%. Pada reaktor 2 dengan susunan media kerikil:pasir kasar:pasir halus:karbon aktif (10:10:15:25) cm mempunyai nilai efisiensi penurunan konsentrasi BOD dan TSS masing-masing adalah 67,01% dan 81,99%. Variasi susunan media yang lebih efektif dalam menurunkan konsentrasi BOD dan TSS pada air limbah domestik adalah reaktor 2 dengan media kerikil:pasir kasar:pasir halus:karbon aktif dengan ketinggian (10:10:15:25) cm.

A biosand filter (BSF) is used as one of the appropriate technology to get purified water in waterpoor countries and developing countries. BSF purifies water to the level of cleanness necessary to be used in daily life and is widely used worldwide, especially given its producibility and simplicity. However, there is a circumstance that pathogens may be included in the formation of schmutzdecke (biofilm) that helps with internal water purification. The environment may be exposed to the pathogens located inside the BSF, causing complications. Pantoea agglomerans found in the biofilm of the BSF were selected as an opportunistic pathogen, and research was conducted to identify and inhibit the biofilm formation of opportunistic pathogens. The natural substances used to inhibit the biofilm formation were garlic extract and moss extract. Moreover, indole, which acts as a signaling molecule in microbes, was also used as a control. The biofilm growth curve of P. agglomerans in vitro was measured and the biofilm formation inhibition abilities of indole and natural extract were confirmed. Subsequently, genes related to biofilm formation and quorum sensing, a method of bacterial communication, were selected, and their expression levels were compared in relation to each other. BSF was produced and applied in an actual filter and water was poured in for 4 weeks to form biofilm. Garlic extract and moss extract were added to each filter, and the gene expressions and colony-forming unit (CFU) counts of the biofilm layer, effluent water, and the source water were compared. Furthermore, 16S rRNA sequencing was carried out. Indole and garlic treatment groups inhibited biofilm formation by 85.37% and 76.99% respectively and when incubated for 18 h, the biofilm formation was reduced to as low as 20%. Each treatment significantly affected gene expression in indole and garlic treatment groups: in both groups, pagI/R was reduced; in the indole treatment group only, bssS increased; and in both groups, ompW increased only at the early stages of biofilm formation. Indole and garlic treatment group’s pagI/R increased in correlation to the duration of incubation. Moss-treated group inhibited biofilm formation rates, CFU counts, and gene expression levels, but to a lower extent than the other groups. P. agglomerans biofilm was inhibited by garlic or indole. The application on the actual filter confirmed the antibacterial effect and anti-biofilm effects of garlic and that the total variety of microbes was also reduced. [ABSTRACT FROM AUTHOR]

Bottom-up public health interventions are needed which are built on an understanding of community perspectives. Project SHINE is a community-based participatory action research intervention focused on developing sustainable water, sanitation, and hygiene strategies with Maasai pastoralists in Tanzania. The aim of the study is to understand perceptions related to water quality and scarcity as well as to assess the potential of the Biosand Filter as a low-cost, low-tech water treatment option. To avoid unintended harms, the community was engaged in identifying potential harms and mitigation strategies prior to the implementation of the filter.Two in-depth interviews and two group discussions were analyzed using thematic content analysis, while three think tanks were analyzed using directed content analysis. The findings highlight a range of concerns regarding water scarcity and quality. The think tank approach was an effective means of engaging the community in identifying potential unintended harms across four dimensions: the physical, psychosocial, economic, and cultural contexts. In addition, two external themes emerged as salient: political harm and harm by omission. [ABSTRACT FROM AUTHOR]

Four household slow sand filters were made out of PVC and operated in continuous and intermittent flows, with and without using a float to control the maximum level of water inside the units. The efficiency was evaluated as a function of Escherichia coli reduction and turbidity in water from the study prepared with kaolinite and E. coli suspension. The correlation of the efficiencies with the following operational parameters was evaluated: operating time, time after maintenance, filtration rate and head loss divided by bed thickness. The filters were classified as intermittent with float (IFF), intermittent without float (IF), continuous with float (CFF) and continuous without float (CF). IFF, CFF and CF had a non-woven blanket installed on top of the media. The results indicated that no significant statistical differences were found in E. coli reduction and turbidity between IFF and IF, however the former had filter runs over 80 days and the latter almost a quarter of this value. CFF matured faster and had less turbidity remaining in relation to CF. When comparing IFF with CFF, the former presented lower turbidity remaining (0.89 ± 0.44 NTU versus 1.24 ± 0.91NTU), but a lower reduction of E. coli (1.40 ± 0.61 log versus 2.29 ± 0.74 log). The time after maintenance was the most important operational parameter when evaluating the efficiencies. The float helped to mature the filter more quickly in a continuous flow and, together with a non-woven blanket, extended the filter runs in the intermittent flow. [ABSTRACT FROM AUTHOR]

In this study, granulated activated charcoal (GAC) and bio charcoal (BC) is used as a filler in P3 biosand bag filter to study their filtration performance against a range of fluoride impurities from 1–1400 mg/L. A set of experiments are done to analyze the filtration efficiency of the sandbag filter against fluoride impurities after incorporating different amounts (e.g., 0.2, 2 kg) and a combination of GAC and BC. A combination of filler GAC and BC (1 kg each) have exhibited excellent results with 100% fluoride removal efficiency against 5 mg/L fluoride impurities for an entire experimental time of 165 min. It is because of the synergetic effect of adsorption caused by the high surface area (739 m2/g) of GAC and hydroxyapatite groups in BC. The data from remediation experiments using individual GAC and BC are fitted into the Langmuir and Freundlich Isotherm Models to check their adsorption mechanism and determine GAC and BC’s maximum adsorption capacity (Qm). The remediation data for both GAC and BC have shown the better fitting to the Langmuir Isotherm Model with a high R2 value of 0.994 and 0.970, respectively, showing the excellent conformity with monolayer adsorption. While the GAC and BC have presented negative Kf values of −1.08 and −0.72, respectively, for Freundlich Model, showing the non-conformity to multilayer adsorption. The Qm values obtained from Langmuir Model for GAC is 6.23 mg/g, and for BC, it is 9.13 mg/g. The pH study on adsorption efficiency of individual GAC and BC against 5 mg/L of fluoride impurities indicates the decrease in removal efficiency with an increase in pH from 3 to 9. For example, BC has shown removal efficiency of 99.8% at pH 3 and 99.5% at pH 9, while GAC has exhibited removal efficiency of 96.1% at pH 3 and 95.9% at pH 9. Importantly, this study presents the significance of the synergetic application of GAC and BC in the filters, where GAC and BC are different in their origin, functionalities, and surface characteristics.

The biosand filter (BSF) is a household sand filter used with pause periods in between uses, but it is not clear if larger sand particles can be used to increase the flow rate while maintaining the same bacterial filtration rate. Smaller scale BSFs were prepared to first measure if larger sand particles can filter water effectively. It was found that after 2 months of ripening BSFs, there was no significant difference in bacterial filtration rate between BSFs of a sand diameter less than 0.7 mm and less than 1.4 mm after 24 h of a pause period. Bacteria were identified by taking 16S rRNA in three layers of the sand in each BSF. Lelliottia sp., Enterobacter aerogenes, Kluyvera sp., Buttiauxellanoackiae, and Pantoea sp. were identified. By examining the band intensities in denaturing gel gradient electrophoresis, it was found that the microbial communities' proportions differ between the levels of the sand and between the two BSFs of differing sand diameters, indicating differing filtration method priorities between the BSFs of different sand sizes. These findings indicate that, in the case of a 24 h pause period, a BSF with sand sizes 1.4 mm or less is just as viable as the current BSFs, while allowing for easier construction. [ABSTRACT FROM AUTHOR]

A household slow sand filter (HSSF) is a widely used water treatment technology recognized as one of the most effective and sustainable in reducing waterborne diseases. However, there is a lack of knowledge concerning its behaviour in the presence of cyanobacteria and cyanotoxins. In this context, the study aimed to evaluate HSSF ability to remove Microcystis aeruginosa cells (stain BB005) and microcystin-LR from water, among other parameters, when operated under continuous (C-HSSF) and intermittent (I-HSSF) flows. C HSSF was operated at a constant filtration rate (1.22 m3 m−2 day−1), while I-HSSF was operated at a variable filtration rate (starting at 2.95 m3 m−2 day−1 and finishing at zero). Each filter produced 60 L day−1. The influence of the pause period was also tested in the I-HSSF. The water from the study was prepared by inoculating M. aeruginosa culture in water from a well to a final cell density of ± 1 × 105 cells mL−1. M. aeruginosa removal rates were 2.39 ± 0.34 log and 2.01 ± 0.43 log by C HSSF and I-HSSF, respectively. Microcystin-LR concentration in studied water was 5.55 μg L−1, and both filters produced filtered water with microcystin concentrations below 1.0 μg L−1, the maximum value recommended by the World Health Organization (WHO), for most of the samples. Turbidity and apparent colour were also within WHO guidelines. Filters operating with different flow regimes and distinct residence times did not statistically influence treatment efficiencies. Both filters showed promising results in the M. aeruginosa and microcystin-LR removals from water; nevertheless, more research is needed to understand the mechanisms involved in the reduction of both cyanobacteria and cyanotoxin through household slow sand filtration. Graphical abstract Image 1 Highlights • Household slow sand filter removed M. aeruginosa and microcystin-LR from the water. • M. aeruginosa removal by filtration exceeded 2 log units. • Microcystin-LR concentrations were below 1.0 μg L-1 for most of the filtered samples. • No significant statistical differences were observed between the filters' efficiencies. [ABSTRACT FROM AUTHOR]

In a world where the consequences of inequalities in access to safe drinking water persist, Household Drinking Water Treatment Technologies (HDWT) remains the most readily available and promising alternative solution to prevent waterborne diseases. While successful cases of combating waterborne diseases with HDWT have been documented, there are also reports of failures in reducing water-related illnesses. Understanding the reasons behind these inconsistent results is crucial. This work aimed to identify and critically discuss barriers, enablers, and technology delivery strategies for HDWT-based interventions to improve drinking water safety. Data from 147 articles covering Solar Disinfection, Chlorination, Flocculation-Disinfection, BioSand Filter, and Ceramic Water Filter were extracted from a total of 11,982 systematically retrieved records. Among the identified factors, 77 barriers and 76 enablers were distributed across different domains: psychosocial (37.7, 47.4%), promotion (22.1, 26.3%), technology (28.6, 10.5%), economic (9.1, 14.5%), and environmental (2.6, 1.3%) for barriers and enablers, respectively. Technology delivery strategies primarily included water education and technology promotion, training for technology usage, provision of HDWT through donation or promotional sale, donation of safe water storage, technical assistance, and the use of a diarrhea control diary. All barriers and enablers affect the initial adoption, regular, and sustained use of HDWT and should be considered when planning and implementing interventions. The health impacts of interventions decreased over time since HDWT adoption. Adequate user training, HDWT donation, and high compliance are important predictors of success for HDWT-based interventions. In general, identifying and exploring the listed enablers can help overcome many of the reported limitations. [Display omitted] • Barriers and enablers to HDWT-based interventions are reviewed and discussed. • Most of the identified factors are psychosocial, promotional and technological. • Notion of risk and fear of drinking untreated water determine the adoption of HDWT. • Regular use of HDWT is conditioned by social norms, attitudes and user skills. • User training, HDWT accessibility, and compliance are good predictors of performance. [ABSTRACT FROM AUTHOR]

The number of people living without access to clean water can be reduced by the implementation of point-of-use (POU) water treatment. Among POU treatment systems, the domestic biosand filter (BSF) stands out as a viable technology. However, the performance of the BSF varies with the inflow water quality characteristics, especially turbidity. In some locations, people have no choice but to treat raw water that has turbidity above recommended levels for the technology. This study aimed to measure the efficiency with which the BSF removes microorganisms from well water and from fecal-contaminated water with turbidity levels of 3, 25, and 50 NTU. Turbidity was controlled by the addition of kaolin to water. Turbidity removal varied from 88% to 99%. Reductions in total coliform (TC) and Escherichia coli ranged from 0.54–2.01 and 1.2–2.2 log removal values (LRV), respectively. The BSF that received water with a higher level of turbidity showed the greatest reduction in the concentration of microorganisms. Additional testing with water contaminated with four bacterial pure cultures showed reductions between 2.7 and 3.6 LRV. A higher reduction in microorganisms was achieved after 30–35 days in operation. Despite the filter’s high efficiency, the filtrates still had some microorganisms, and a disinfection POU treatment could be added to increase water safety.

Water is essential for life. Without water, not only, no one can survive but it also affects health, education and well being of a person. Industrialization, climate change and other environmental factors contributes in contamination of water. Access to safe potable water is basic human right for drinking, and other purposes. Filtration through biosand filter is among one of several methods for the purification of contaminated water. Biosand filter is easy to construct, use and maintain. It can be made from local materials and is also low in cost. The purpose of this study was to investigate the effectiveness of the biosand filter. In this study 30 samples were run to detect the effectiveness of biosand filter. Results suggest that biosand filter effectively reduced microbial load up to 98%. It is also effective in removing suspended particles, turbidity and other impurities from water and improves the taste and quality of water for drinking, sanitation and other purposes.

To successfully prevent diarrheal pathogen transmission, a variety of causal pathways should be considered. This study utilized a suite of tools to identify primary factors associated with diarrheal occurrences in a set of communities in Para, Brazil that had received a biosand filter (BSF). First, existing Demographic and Health Survey data sets from the departments of Para and Amazonas, Brazil were analyzed using three statistical techniques, namely: Mahalanobis-Taguchi Strategy, canonical correlation analysis, and latent factor regression. Second, results of statistical analyses were combined with a literature review and field observations to locally adapt a previously validated structural equation model (SEM) originally developed for Quiche, Guatemala. Third, a randomized household survey was used to collect data—including water sources, sanitation facilities, hygiene practices, socioeconomic statuses, education levels, BSF maintenance, and diarrheal occurrences—in Para, Brazil and analyzed with the hypothesized SEM. Household education level had the largest significant negative effect size on diarrheal occurrence, while improved water source had the largest positive significant effect size. Maintenance of the BSF in the home had a negligible effect size on diarrheal occurrence. Complex associations observed in the SEM between diarrheal occurrence and a variety of causal pathways support the view that a multibarrier intervention is warranted. [ABSTRACT FROM AUTHOR]

The purpose of this study was to assess factors associated with Escherichia coli (E. coli) contamination in rural households in Cambodia that have adopted household water treatment. The following factors were significantly associated (α < 0.05) with apparent E. coli contamination: cleaning the drinking vessel with untreated water, not drying the cup (with a cloth), accessing treated water by the use of a scoop (ref: using a tap), having more than one untreated water storage container, having an untreated water storage container that appeared dirty on the outside, and cows living within 10 m of the household. This study provides further evidence confirming previous studies reporting an association between inadequate cleanliness of water storage containers and household drinking water contamination, and identifies practical recommendations statistically associated with reduced post-treatment E. coli contamination in the household setting in rural Cambodia. [ABSTRACT FROM AUTHOR]

The biosand filter is a household-level water treatment technology used globally in low-resource settings. As of December 2016, over 900,000 biosand filters had been implemented in 60 countries around the world. Local, decentralized production is one of the main advantages of this technology, but it also creates challenges, especially in regards to quality control. Using the current recommended proportions for the biosand filter concrete mix, slump was measured at water-to-cement ratios of 0.51, 0.64 and 0.76, with two replicates for each level. Twenty-eight-day strength was tested on four replicate cylinders, each at water-to-cement ratios of 0.51, 0.59, 0.67 and 0.76. Wet curing and dry curing were compared for 28-day strength and for their effect on shrinkage. Maximum strength occurred at water-to-cement ratios of 0.51-0.59, equivalent to 8-9.3 L water for a full-scale filter assuming saturated media, corresponding to a slump class of S1 (10-40 mm). Wet curing significantly improved strength of the concrete mix and reduced shrinkage. Quality control measures such as the slump test can significantly improve the quality within decentralized production of biosand filters, despite localized differences in production conditions. [ABSTRACT FROM AUTHOR]

The Household Slow Sand Filter (HSSF) is a Point-Of-Use technology that has several technical, constructive, and operational advantages, which allows users to improve the quality of their own drinking water at home. This paper aims to provide results concerning the real possibility of treating surface water using HSSF with two feeding strategies, covering more than one year of operation (430 days), including seasons with different inputs on surface water. To do this, we compared the intermittent (HSSF-I) and the continuous (HSSF-C) feeding strategies in quantitative terms (filtered water quality and treatment efficiency) and qualitative terms (construction, cost, and operational challenges). Overall, both HSSF models were efficient and improved the water quality, but HSSF-C produced better quality filtered water in terms of turbidity (73 (± 20)% versus 69 (± 18)%), Escherichia coli (2.06 (± 0.60) log versus 1.65 (± 0.78) log), Giardia cysts (>3 log versus 2.89 (± 0.32) log), and Cryptosporidium oocysts (1.22 (± 0.10) log versus 0.95 (± 0.45) log) than HSSF-I. In addition, HSSF-C was able to remain more stable throughout the entire operation, without major impacts caused by influent water variations and maintenance activities. On the other hand, HSSF-I was cheaper, took up less space in the house, had a simple and easy operation, and did not require as much maintenance as the continuous one. Results indicated that HSSF-C may be a more viable model for treating surface water, but it still needs to improve its transfer requirements and assess its user acceptability from field experiences. [Display omitted] • Household slow sand filters treated surface water for 430 consecutive days. • Both operating regimes removed turbidity, E. coli , and protozoa from surface water. • Continuous feeding strategy is more efficient and intermittent is more practicable. • Maintenance frequency is the biggest operational challenge of the HSSF-C. • The microorganisms' passage through the bed is the biggest issue of HSSF-I. [ABSTRACT FROM AUTHOR]

One of the most pressing problems in rural areas is drinking water that has been contaminated with arsenic and other organic and inorganic pollutants. A significant risk of arsenic toxicity remains for many rural populations due to inadequate public awareness campaigns regarding the health impacts of consuming arsenic-contaminated water. As a result, inexpensive techniques are essential to eliminate arsenic from water. The feasibility of iron oxide coated biosand filtration for eliminating As5+ from aqueous solutions was examined in this study through batch and semi-continuous tests. An iron oxide coated biosand filter showed the best arsenate removal efficiency, with up to 99.8% removal over 120 days. The adsorption rate tended to increase with the adsorbent dosage. Experiments at different iron oxide dosages confirmed that the adsorption of arsenate onto iron oxide particles followed a pseudo second-order model. Langmuir and Freundlich models were used to describe the adsorption capacity, and both models showed a good fit (R2 >0.90) to the adsorption of arsenate at different levels of water hardness. After filtration, a leachability test was performed on the spent iron and sand particles. The results indicated that the leachate contained low arsenate concentrations, and should be carefully treated as hazardous waste. [Display omitted] • Efficiencyof the biosand filter is increased by the addition of a layer of sand coated in iron oxide. • Iron coated biosand efficiently removed As5+ from synthetic ground water. • Langmuir and Freundlich models showed a good fit to the adsorption of As5+. • Adsorption rate tended to increase with the adsorbent dosage. • Iron coated biosand demonstrated an As5+ removal efficiency of 99.8% over 120 days. [ABSTRACT FROM AUTHOR]

Slow sand filters were first used for safe drinking water provision during the 19th century. The technology has been gradually improved and utilized at several scales. Based on their intrinsic limitations other filtration systems have been developed, including membrane technologies. The universal applicability of filtration in drinking water supply makes filters a device of choice to facilitate the achievement of the UN Sustainable Development Goals (‘drinking water for all by 2030’). Available strategies to rationally design efficient and sustainable water filters are scattered in the literature and are difficult to access and evaluate by starting researchers. The present Special Issue summarizes knowledge on two key filtration systems for drinking water supply: (i) membrane technology and (ii) metallic iron based filters. The five (5) accepted articles are being briefly presented herein.

Contamination of groundwater wells by arsenic is a major problem in China. This study compared arsenic removal efficiency of five sand-based point-of-use filters with the aim of selecting the most effective filter for use in a village in Shanxi province, where the main groundwater source had arsenic concentration >200 μg/L. A biosand filter, two arsenic biosand filters, a SONO-style filter and a version of the biosand filter with nails embedded in the sand were tested. The biosand filter with embedded nails was the most consistent and effective under the study conditions, likely due to increased contact time between water and nails and sustained corrosion. Effluent arsenic was below China's standard of 50 μg/L for more than six months after construction. The removal rate averaged 92% and was never below 86%. In comparison, arsenic removal for the nail-free biosand filter was never higher than 53% and declined with time. The arsenic biosand filter, in which nails sit in a diffuser basin above the sand, performed better but effluent arsenic almost always exceeded the standard. This highlights the positive impact on arsenic removal of embedding nails within the top layer of biosand filter sand and the promise of this low-cost filtration method for rural areas affected by arsenic contamination. [ABSTRACT FROM AUTHOR]

The present study develops membrane hybrid system for drinking water that combines a trickling filter (TF) and a thin-layer biosand filter (TBSF) prior to membrane. Two different types of trickling filter (submerged and protruding) were placed before the biosand filter (BSF) with two different sand depths (40 and 3 cm). The effectiveness of the TBSF was measured in terms of the reduction in levels of total organic carbon, turbidity, Escherichia coli, and bacteriophage MS2. The hybrid systems with a TF + BSF + MF membrane showed higher TOC removal and turbidity reduction than hybrid systems only with BSF + MF membrane. The TOC removal and turbidity reduction by the hybrid systems with a TF were much more stable than those of hybrid systems without a TF throughout the operating period despite the changing level of the TOC. The removal of E. coli by hybrid systems with a TF was greater (usually >99.99%) and more stable than that by the hybrid systems without a TF. However, the removal of bacteriophage MS2 by the hybrid systems with a TF was only moderate (~99%) and not greatly different from that by the hybrid systems without a TF. [ABSTRACT FROM AUTHOR]

The performance of a vinegar-amended anaerobic biosand filter was evaluated for future application as point-of-use water treatment in rural areas for the removal of arsenic and nitrate from groundwater containing common ions. Due to the importance of sulfate and iron in arsenic removal and their variable concentrations in groundwater, influent sulfate and iron concentrations were varied. Complete removal of influent nitrate (50 mg/L) and over 50% removal of influent arsenic (200 μg/L) occurred. Of all conditions tested, the lowest median effluent arsenic concentration was 88 μg/L. Iron removal occurred completely when 4 mg/L was added, and sulfate concentrations were lowered to a median concentration <2 mg/L from influent concentrations of 22 and 50 mg/L. Despite iron and sulfate removal and the establishment of reducing conditions, arsenic concentrations remained above the World Health Organization's arsenic drinking water standard. Further research is necessary to determine if anaerobic biosand filters can be improved to meet the arsenic drinking water standard and to evaluate practical implementation challenges. [ABSTRACT FROM AUTHOR]

Access to safe drinking water is still unavailable to many people in developing countries. Biosand filter (BSF) is one of the most promising emerging point of use technologies. A large amount of organic matters is contained in their water source. The purpose of this study is to develop a hybrid BSF system, called as a trickling biosand filter (TBSF), which is combined with rock media as trickling filter to reduce organic matters ranged from CODcr 50 to 150 mg/L in source water. The effects of TBSF and BSF on the factors as CODcr, flux, turbidity, and DO are analyzed. Results showed that the effluent CODcr of TBSF was obtained 2.3–4.2 mg/L during 41 d. However, that of BSF fluctuated within 13.1–28.6 mg/L. DO in standing water of TBSF increased to average 7.8 mg/L while that of BSF decreased to average 1.2 mg/L. DO played an important role to activate microbial activity in trickling filter and to ripen Schmutzdecke layer to decrease constantly turbidity andEscherichia coli(E. coli) in TBSF, though shock loading of organic matters occurred. The turbidity could be removed well if it was originated from organic matters. Removal ofE.coliin BSF was fluctuated because of low DO. This could not provide perfect microbial layer on top sand and allowE.colipassing through sand filter, though enough time for ripening. [ABSTRACT FROM AUTHOR]

Safe drinking water remains a major global challenge, especially in rural areas where, according to UNICEF, 80% of those without access to improved water systems reside. While water, sanitation, and hygiene (WASH)-related diseases and deaths are common outcomes of unsafe water, there is also an economic burden associated with unsafe water. These burdens are most prominent in rural areas in less-developed nations. Slow sand filters (SSFs), or biological sand filters (BSFs), are ideal water treatment solutions for these low-resource regions. SSFs are the oldest municipal drinking water treatment systems and improve water quality by removing suspended particles, dissolved organic chemicals, and other contaminants, effectively reducing turbidity and associated taste and odor problems. The removal of turbidity and dissolved organic compounds from the water enables the use of low-cost disinfection methods, such as chlorination. While the working principles of slow sand filtration have remained the same for over two centuries, the design, sizes, and application of slow sand filters have been customized over the years. This paper reviews these adaptations and recent reports on performance regarding contaminant removal. We specifically address the removal of turbidity and microbial contaminants, which are of great concern to rural populations in developing countries.

In many developing countries, inadequate access to safe drinking water is a major cause of morbidity and mortality. Furthermore, approximately 100 million people worldwide are exposed to arsenic (As) in drinking water. The World Health Organization is thus now encouraging the development and supply of a low-cost technology that can treat domestic water. The present study combined the use of a trickling filter (TF) with a biosand filter (BSF). Additionally, to remove As (V) from water, the use of the absorbents Fe–Mn–Si (FM-α) and zero-valent iron was experimentally investigated. Different compositions of influent were supplied in five stages. Efficiency was analyzed in terms of the total organic carbon, turbidity, UV 254 , As (V) content, flux, power consumption, total solids, and volatile solids of samples taken from four treatment systems (M-1: membrane, M-2: BSF + membrane, M-3: TF + membrane, and M-4: TF + BSF + membrane). Results show that the removal of organic matter and decline in flux over 45 d reduced in the order M-4 > M-2 > M-3 > M-1. The combination of TF, BSF, and M-4 was shown to have the most stable operation even under shock loading. The biofilm of the BSF and sieving effect played an important role in reducing the content of organic matter. The recovered flux of M-1 decreased and the M-1 membrane was backwashed four times. In comparison, M-3 required backwashing four times, M-2 required backwashing once, and M-4 did not require backwashing during operation. The M-4 system removed 95% of organic matter without any cleaning of the top soil throughout the experiment and reduced turbidity by 99%. Between systems M-1 to M-4, the most effective system was M-4 because of its stable operation without backwashing of the membrane throughout the experimental period. The M-2 system with FM-α embedded in the layers of sand removed 77% of As (V), while the M-4 system, using zero-valent iron adsorbents, removed 97% of As (V). [ABSTRACT FROM AUTHOR]

Efficiency of a household plastic biosand filter (BSF) for the removal of turbidity and fecal contamination was evaluated. Water of river Ravi was used as influent. Water filtered through BSF was further treated using Solar Disinfection (SODIS). The study was conducted for raw water with low pollution level (total coliforms <500 MPN/100 ml) and high pollution level (total coliforms between 500-20,000 MPN/100 ml). The average value of turbidity removal by BSF was 94.5 % with 0.9 NTU as average turbidity of effluent. For raw water with low pollution level, the BSF was able to achieve a maximum of 2.2 log10 unit reduction (99.4 %) for total coliforms (39 MPN/100 mL in effluent) and 1.95 log10 unit reduction (98.5 %) for fecal coliforms (9 MPN/100 mL in effluent). While for raw water with high pollution level, the maximum removal of 1.5 log10 unit (97.5 %) for total coliforms (1430 MPN/100 mL in effluent) and 1.8 log10 units (98.4 %) for fecal coliforms (387 MPN/100 mL in effluent) was achieved in BSF. To make the effluent fit for drinking it was further treated using SODIS, which rendered the BSF effluent fit for drinking with zero fecal coliforms count (for full sunny and partially cloudy conditions). Newly proposed plastic BSF could be a good replacement of already used concrete household BSF (used in more than 63 countries) being cheaper in cost and lighter in weight by 85% and 80%, respectively than the concrete BSF. [ABSTRACT FROM AUTHOR]

Point-of-use (POU) water treatment provides households in rural and remote communities with a means of obtaining greater control over their water quality and its effects on human health. One of the most prevalent POU interventions, the BioSand filter (BSF), is a household-scale, intermittently operated slow sand filter used by over 300,000 households. The sand and gravel media within BSFs can be housed in concrete (cBSF) or Hydraid plastic (pBSF) bodies, with the latter becoming increasingly popular due to their portability, durability, and anticipated scalability. This study evaluated whether pBSFs, which are lighter and thinner than their concrete counterparts, can maintain their integrity and performance after being subjected to disturbances that could occur in a typical household. Eight pBSFs and two cBSFs were run in parallel for 13 weeks, and three disturbances - one-time filter movement, one-time side impacts, and daily bucket impacts - were applied. Moving and side impacts affected pBSFs more dramatically than cBSFs, causing marked decreases in sand column height (6-29 mm decrease, p<0.001) and decreases in maximum initial flow rate (18-84% decrease, p <0.001). Brief spikes in pBSF effluent turbidity (0.98-15.2 NTU greater than mean effluent levels) also occurred immediately after disturbances. [ABSTRACT FROM AUTHOR]

An estimated 1.6 million people die from diarrheal diseases each year due to lack of access to safe water and sanitation, and persons with physical disabilities face additional barriers. In Cambodia, approximately 5% of the population is disabled, presenting substantial obstacles in accessing these basic services. The purpose of this study was twofold: first, to identify the challenges facing persons with physical disabilities in accessing safe household water and basic hygiene in rural Cambodia; and, second, to use these results to generate policy and practice recommendations for the water and sanitation hygiene sector implementing water treatment system interventions in rural settings. Fifteen field interviews were conducted with persons with physical disabilities. Thematic analysis was used to identify six main themes. The results indicated that environmental barriers to access were greater in the workplace than household settings and those persons with disabilities had greater awareness about safe drinking water compared to basic hygiene. Additionally, lack of physical strength, distance to water, and lack of financial means were noted as common access barriers. The findings support ongoing research and offer insight into the particular challenges facing persons with physical disabilities in rural areas in accessing safe drinking water and basic hygiene. [ABSTRACT FROM AUTHOR]