Article

Use and performance of BioSand filters in Posoltega, Nicaragua

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Abstract

An evaluation of BioSand Filters, a method of Household Water Treatment, was conducted in Posoltega, Nicaragua, with objectives of determining the long-term filtration efficiency and the rate of sustained use. Field methods included microbial and turbidity water quality testing and interviews with filter users regarding the operation, maintenance and perceptions towards the filters. Of the 234 BioSand Filters installed in 1999 and 2004, only 24 were found to still be in operation. The average filtration efficiency was found to be 98% for total coliforms, 96% for E. coli and 88% for turbidity. Statistically significant effects on filtration efficiency were detected for the source contamination, the inverse of the flow rate, and the standing depth of water over the sand. A follow-up laboratory QA/QC procedure was undertaken to validate the field methods, which consisted of membrane filtration (MF) with m coliBlue24 growth media, and SolarCult dipslides. It was found that MF with m coliBlue24 produced useful reproducible results, and is an appropriate method for conducting field water quality testing. The dipslides were found to be an appropriate tool for testing source water quality and assessing the applicability of BioSand Filters, and may be an appropriate tool for local health representatives to promote safe water practices within the community. However, the dipslides should not be used as a presence / absence test for drinking water due to the high limit of detection. The low rate of sustained use (10%) is mostly a result of the structural failure of the concrete walls of the filter, in particular for those filters from 2004. Anecdotal evidence suggests insufficient quality control during the construction. The filtered water and the stored post-filtered water did not meet the WHO guidelines for safe drinking water on account of the presence of E. coli. Also identified were improper maintenance practices and unsafe storage of post-filtered water. These problems could have been addressed through the development of a holistic water system approach, such as the World Health Organization Water Safety Plan.

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... Concerning the quantity of the water treated (20 L/h), this volume gives satisfaction to the communities because it covers a lot. This level of population opinion about the BSF was higher than that obtained in Nepal (89%) by Paynter (2001), but slightly lower than that obtained in Haïti (99%) and in Nicaragua (100%) (Vanderzwaag, 2008). Concerning the utilization of the water produced by the BSF, communities used them for drinking, bathing, cooking and housework. ...
... The variation of the results between these two works could be explained by the raw water quality and the manner that experiments have been conducted by the authors. Furthermore, the treatment efficiency achieved in this work with the BSF is within the same order of results in literature (50 to 90%) (Vanderzwaag, 2008). Comparing the NH 4 + , NO 2 and NO 3 concentrations of the BSF effluents, one could find that they are lower than WHO drinking water standards (WHO, 2008). ...
... After their filtration on the BSF, the entire microorganism colonies were removed (100%). The mechanisms implicated in bacteria removal by the BSF could be: adsorption, physical straining and natural die-off of the microbial because of lack of carbon source (Elliott et al., 2006 2007; Vanderzwaag, 2008;Fiore et al., 2010). ...
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A concrete biosand filter (BSF) was designed, and its performance was evaluated on three different water used in the rural communities. The field study was conducted by using tap, well and pump waters, and a questionnaire was administered to apprehend the community’s attitudes in the BSF utilisation. BSF performance was characterised by analysing the filtrates concentration in NH4+, NO3- , NO2-, COD, Escherichia coli, and Clostridium perfringens. The BSF was approved by 94% of the population for water quality, ease of use and quantity of clean water produced. The main results are effective removal of microorganisms (C. perfringens, E. coli), chemical transformation and removal of NH4+, NO3- and COD at concentrations below WHO drinking water standards. BSF technology could be a solution in the provision of portable water to rural areas and might represent an alternative for the use of expensive bottled water.
... This confusion and maintenance problems have been shown to negatively impact sustained use of BSFs by families. For example, biosand filters installed near Posoltega, Nicaragua, had a sustained use rate of only 10% (Vanderzwaag 2008). Specifically, 10 of 34 BSFs from 1999 and 14 of 200 BSFs distributed in 2004 were still in use in early 2007. ...
... Recontamination of the water in storage vessels is sometimes a problem. A field study in Nicaragua found that the average total coliforms in the source water were 10 4 CFU/100 mL, 250 CFU/100 mL in filtered water, but 3000 CFU/100 mL in stored water (Vanderzwaag 2008). Similar results were found with E. coli: 120, 6, and 60 CFU/100 mL in source water, filtered water, and stored water, respectively. ...
Article
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Safe drinking water is a critical need in developing communities around the globe. A variety of disinfection methods can be used at a community scale or as household water treatment. It is important that such methods are appropriate and sustainable for the environmental, economic, and societal constraints of each setting. This chapter highlights some of the methods commonly used in developing communities and compares their documented disinfection effectiveness in laboratory tests and field use. The strengths and weaknesses of each approach in regards to the removal and/or inactivation of bacteria, viruses, and protozoans are compared. Community scale methods reviewed include slow sand filtration, riverbank filtration, and solar-based approaches. Commonly used household treatment methods, also called point-of-use (POU) treatment, that are reviewed include chemical treatment, biosand, ceramic water filters, and solar disinfection. Global application of POU methods is increasing, but their long-term use and effectiveness is generally poorly documented. Many of these methods are undergoing increasing levels of research, but performance differences between the lab and field studies are a concern. A few studies have also documented health benefits associated with the use of these treatment methods; however, more research of this type is also needed.
... BSF technology had been favourably accepted by users, on a number of counts: † Considerable improvement in taste, odour and appearance of the water was evident (Vanderzwaag 2007). † Like other filtration technologies, BSF does not introduce chemicals into the water. ...
... Chemicals such as chlorine may affect its acceptability due to objections about taste and odour (Clasen 2008). † The health of the family was perceived to have improved after using the filter (Vanderzwaag 2007). † BSF is able to operate well under a wide range of conditions, such as temperature, pH and turbidity. ...
Article
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... [4][5][6]9,10 However, although BSFs use simple technology that has been proven appropriate for many developing countries, few field studies have evaluated how effective and sustainable they are beyond six years. [11][12][13] As a result, there is currently little empirical evidence that BSF technology is effective and sustainable in the long term. ...
... These results are consistent with those of similar BSF field studies worldwide. 4,6,7,9,[11][12][13][22][23][24][25][26] Although flow rates were lower than those recorded in 2005, many users did not seem to mind and continued to clean and use their filters regularly, even though clogging was reported as leading to disuse in some filters. 20 That filtered water was found with higher E. coli concentrations than source water in three instances was not surprising and shows that in reality, filters may not always be properly functioning. ...
Article
Full-text available
A field study assessing the sustainability and efficacy of 55 biosand filters installed during 1999-2010 was conducted in the Artibonite Valley, Haiti during 2011. Twenty-nine filters were still in use. Duration of filter use ranged from < 1 to 12 years. Water quality, microbial analysis, and flow rate were evaluated for each functioning filter. Kaplan-Meier analysis of filter lifespans showed that filter use remained high (> 85%) up to seven years after installation. Several filters were still in use after 12 years, which is longer than documented in any previous study. Filtered water from 25 filters (86%) contained Escherichia coli concentrations of < 10 most probable number of coliforms/100 mL. Recontamination of stored filtered water was negligible. Bacterial removal efficiency was 1.1 log(10). Comparable results from previous studies in the same region and elsewhere show that biosand filter technology continues to be an effective and sustainable water treatment method in developing countries worldwide.
... An evaluation of BSFs to determine the long-term filtration efficiency and the rate of sustained use was conducted in Posoltega, Nicaragua. Although in this earlier study was reported that the average filtration efficiency was found to be 98% for total coliforms, 96% for E. coli and 88% for turbidity (Vanderzwaag 2008), the mathematical models to calculate the design's parameters are still not fully understood . Important considerations in the development of models are the availability and use of equations to calculate the depth of sand filter and water velocity. ...
... An evaluation of BSFs to determine the long-term filtration efficiency and the rate of sustained use was conducted in Posoltega, Nicaragua. Although in this earlier study was reported that the average filtration efficiency was found to be 98% for total coliforms, 96% for E. coli and 88% for turbidity (Vanderzwaag 2008), the mathematical models to calculate the design's parameters are still not fully understood . Important considerations in the development of models are the availability and use of equations to calculate the depth of sand filter and water velocity. ...
... Water can then be safely consumed almost immediately, and the health improvements are large (Clasen & Bastable, 2003;Clasen, Roberts, Rabie, Schmidt, & Cairncross, 2006;Fewtrell et al., 2005). Vanderzwaag (2008) reports high breakage rates for filters in Nicaragua, but this does not appear to be a common problem. ...
... An evaluation of BSFs to determine the long-term filtration efficiency and the rate of sustained use was conducted in Posoltega, Nicaragua. Although in this earlier study was reported that the average filtration efficiency was found to be 98% for total coliforms, 96% for E. coli and 88% for turbidity (Vanderzwaag 2008), the mathematical models to calculate the design's parameters are still not fully understood . Important considerations in the development of models are the availability and use of equations to calculate the depth of sand filter and water velocity. ...
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