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From design to implementation : innovative slow sand filtration for use in Developing countries
Abstract and Figures
During January 2002, the author traveled to Nepal to evaluate the Biosand Filter Pilot
Project, which introduced 12 innovative intermittently operated slow sand filters into homes and schools in 5 different villages of the Lumbini District. In addition, she assessed the microbial contamination of tubewells in 17 villages including those with Biosand filters, which are part of the International Buddhist Society (IBS) health outreach program. Constructed in the Nawalparasi District by Nepalese Durga Ale, Biosand filters and their media were transported to Lumbini villages where they were commissioned during the first week of January 2002. While technically sound procedures were followed for both filter construction and commissioning, the importance of protecting the biofilm and schmutzdecke did not seem to be understood. Filter owners expressed a desire to become more educated about their filters as basic filter operation and maintenance did not appear to be practiced. In addition, flow rates dropped sharply following installation, which suggests a problem with the sand source or sand preparation procedure.
Expanding the Lumbini Biosand Pilot Project offers an opportunity to refine the existing Biosand construction, distribution, and education process. Recommendations include improving sand preparation, involving the community in media sifting and washing, disinfecting the filter standpipe using chlorine solution, flushing filters with -100L of water following installation and cleaning, and preparing and translating standardized Biosand filter training materials based on 8 key educational points.
Well field-testing in the 17 IBS villages consisted of 109 samples analyzed for H2S producing bacteria and enumeration of 67 fecal coliform and 23 E.coli samples using the membrane filtration technique. Public wells, in general, were found to offer much safer drinking water than private wells with 20% of public wells and 39% of private wells testing positive for fecal coliform bacteria. More importantly, the concentration range of private tubewell fecal coliform bacteria was found to be much greater (lcfu/100ml to 500 cfu/100ml) than that of public wells (1cfu/100ml to 14cfu/100ml).
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... with an altitude of 1734 m ASL. Te variables considered for the combined system's design and construction were the required water quality, hydraulic loading rate (HLR), hydraulic retention time (HRT), substrate, and vegetation [36,37]. ...
... Applying sand or gravel that has not been properly washed or that is of the wrong grain size may be the cause of persistent or frequent flter clogging. To ensure a good fow, the pipes should be regularly inspected [36,51]. For organic flters, service life is an especially crucial factor to take into account. ...
Most countries around the world have experienced water scarcity in recent decades as fresh water consumption has increased. However, untreated wastewater is routinely discharged into the environment, particularly in developing countries, where it causes widespread environmental and public health problems. The majority of wastewater treatment method publications are heavily focused on high-income country applications and, in most cases, cannot be transferred to low and middle-income countries. An experimental study was conducted to evaluate the performance efficiency of pilot-scale physicochemical and biological treatment methods for the treatment of household greywater in Jimma, Ethiopia. During the experiment, grab samples of greywater were taken from the combined treatment system’s influent and effluent every 7 days for 5 weeks and analyzed within 24–48 hours. Temperature, DO, EC, turbidity, TDS, and pH were measured on-site, while BOD, COD, TSS, TP, TN PO4−3-P, NO3-N, NH4-N, Cl−, and FC were determined in the laboratory. During the five-week pilot-scale combined treatment system monitoring period, the combined experimental and control system’s mean percentage reduction efficiencies were as follows: turbidity (97.2%, 92%), TSS (99.2%, 97.2%), BOD5 (94%, 57.4%), COD (91.6%, 54.7%), chloride (61%, 35%), TN (68.24, 42.7%), TP (71.6%, 38.7%), and FC (90%, 71.1%), respectively. Similarly, the combined experimental and control systems reduced PO4−3-P (12.5 ± 3 mg/L), NO3-N (4.5 ± 3 mg/L), and NH4-N (10.19 ± 2.6 mg/L) to PO4−3-P (3.5 ± 2.6 mg/L, 7.5 ± 1.6 mg/L), NO3-N (0.8 ± 0.5, 3.6 ± 2.3 mg/L), and NH4-N (7 ± 2.9 mg/L, 15.9 ± 3.9 mg/L), respectively. From the biofiltration and horizontal subsurface flow constructed wetland combined systems, the experimental combined technology emerged as the best performing greywater treatment system, exhibiting remarkably higher pollutant removal efficiencies. In conclusion, the combined biofiltration and horizontal subsurface flow constructed wetland treatment system can be the technology of choice in low-income countries, particularly those with tropical climates.
... Finally, there is a paradox associated with the intangible nature of water treatment, especially in communities where the germ theory of disease is not widely known or accepted; while an acceptable system should not significantly alter the taste, odor, or appearance of water, the ability of users to smell, taste, or see evidence that the technology is "working" may be indispensable (Lukacs 2001). ...
... Biosand filters, which rely upon natural biofilms to disinfect water as it percolates slowly through a layer of sand, are generally effective but can easily become clogged, dramatically reducing their flow rate (Lukacs 2001), and their effectiveness can be diminished under field conditions (Sobsey 2002). Solar disinfection, or SODIS, though not without its own disadvantages, is a simple, inexpensive, and effective addition to the POU water treatment repertoire. ...
Sunlight efficiently disinfects drinking water in plastic bottles over two days, but simple additives may show promise for reducing this time to several hours. This study found that adding up to 500 [micro]M hydrogen peroxide accelerates the room-temperature inactivation of E. coli K12 by sunlight at a rate proportional to concentration, while temperatures of 35 and 45 degrees Celsius further enhance this effect. It was also found that both 25 [micro]M ascorbic acid in the presence of 2.5 [micro]M copper sulfate and solid copper metal in the presence of 200 [micro]M ascorbate synergistically increased the light-mediated inactivation rate with first-order dependence in both dissolved species, while the addition of hydrogen peroxide to this system exhibited further synergistic enhancement. Although solid copper and 1% lemon juice performed no better than lemon juice alone, the latter significantly accelerated inactivation in a light-dependent manner. Finally, at higher concentrations the copper-ascorbate system can also inactivate E. coli in the dark. These findings suggest possible directions for accelerating the rate of SODIS, with potential for the Cu + ascorbate system to act as a residual disinfectant and an alternative to SODIS on extremely cloudy days.
... 73 The project was only partially successful, however; evaluators found that the technology failed on multiple occasions because local users had trouble constructing the technologies themselves and protecting some of its components from environmental pollutants. 74 The unfamiliarity of the technology made it difficult for local citizens to use. In sum, citizens struggled to build and use this technology in part because outside scientists and engineers played the primary role in design and development. ...
... Lukacs (2002),Duke et al. (2006),CAWST (2007) and Hillman(2007)20 -70 Elliott et al. et al. (2008) Under-drain (mm) 50Elliott et al. (2008) Start-up time (days) 14 -21 CAWST (2007) and Hillman(2007)p ...
A biosand filtration (BSF) unit is an intermittently operated slow sand filter designed for household use. This paper reviews the practical application of BSF, identifies the important design considerations and proposes a systematic design procedure. The media properties, water requirements, filter cycle time and water temperature are identified as the most important design input parameters. The resultant specifications are the water dosage volume, water production rate and media bed dimensions. We propose two parameters for characterising the filtration rate, namely the initial and average clean bed filtration rate. Mathematical expressions for these two parameters and the filtration time are derived. Guideline values for the filtration rate and the ratio of the pore volume to the water dosage volume are established and used as design checks. It is noted that the filtration rate is determined solely by the properties of the water temperature and the media-customary constraints posed by the bed area and the bed depth had been eliminated. Therefore the heart of BSF design lies in the careful and appropriate selection of the filter media. The design procedure proposed is illustrated with an example for a typical rural household in Venda, South Africa.
Bio-sand filters (BSFs) are point-of-use (POU) potable water filtration
systems commonly used in low-income communities at household level. The
principle of operation is similar to that of a slow sand filter and the major
difference is that they are operated intermittently at the POU. It
is one of the emerging low-cost technologies which makes use of readily and
locally available construction materials but is poor in the removal of
nitrates. In order to enhance the removal of nitrates through
denitrification, a modified BSF with ethanol as an external
carbon source at C / N ratios of 1.1 and 1.8 was investigated. In the
absence of an external carbon source, the nitrate removal efficiency was
32 %, whilst removal efficiencies at C / N ratios of 1.1 and 1.8
were 44 and 53 % respectively. The inflow rate reduced significantly
from an initial flow rate of 0.04 to 0.01 m3 h−1. The
reduction in the inflow rate was mainly due to the growth of the biological
layer on the filter media. The study showed that the use of an external
carbon source like ethanol in bio-sand filtration enhances the removal of
nitrates in potable water.
In recent decades, most countries of the world have experienced a shortage of water and increase its rate of consumption. Today, every country in the world are interested in this problem by trying to find alternatives to address this shortage. One solution is reuse greywater (GW) for irrigation after treatment. GW is all water generated from Household except toilet water. The risks associated with the reuse of these waters are the presence of pathogens that can infect humans, animals and plants. In this thesis focused on studying treatment by slow sand filtration and the survival of representatives of pathogens, such as E. Coli, P. aeruginosa , E. Faecalis and Bacteriophage MS2 which could be found in the greywater. The study factors was a physico-chemicals factors such as; temperature (6±2,23±2,42±2°c), salinity (1.75 and 3.5% Nacl), oxygen (aerobic and anaerobic condition), nutrient ( rich media , 50%: 50% salt and poor media ), light with photocatalysis ( UV and Visible lights) and slow sand filter (Egyptian desert sand and swimming pool sand). A combination of high temperature, sunlight and photocatlysis are mainly responsible for the rapid decline of bacteria and MS2 coliphage. Slow sand filter have clearly less influence on the survival of bacteria in the greywater, but it effective to decline turbidity and COD for short times.
BACKGROUND: Access to safe drinking-water is a fundamental requirement for good health and is also a human right. Global access to safe drinking-water is monitored by WHO and UNICEF using as an indicator "use of an improved source," which does not account for water quality measurements. Our objectives were to determine whether water from "improved" sources is less likely to contain fecal contamination than "unimproved" sources and to assess the extent to which contamination varies by source type and setting. METHODS AND FINDINGS: Studies in Chinese, English, French, Portuguese, and Spanish were identified from online databases, including PubMed and Web of Science, and grey literature. Studies in low- and middle-income countries published between 1990 and August 2013 that assessed drinking-water for the presence of Escherichia coli or thermotolerant coliforms (TTC) were included provided they associated results with a particular source type. In total 319 studies were included, reporting on 96,737 water samples. The odds of contamination within a given study were considerably lower for "improved" sources than "unimproved" sources (odds ratio [OR] = 0.15 [0.10-0.21], I2 = 80.3% [72.9-85.6]). However over a quarter of samples from improved sources contained fecal contamination in 38% of 191 studies. Water sources in low-income countries (OR = 2.37 [1.52-3.71]; p
A non-randomized assessment of long-term biosand filter (BSF) use and sustainability in the Artibonite Valley near Deschapelles, Haiti was conducted during March, 2011. Of the 55 BSFs visited, 47% were no longer in use. Filter lifespan ranged from <1 year to systems still in use after 12 years. Interviews with BSF owners revealed problems related to intermittent filter use due to travel for employment or personal matters; broken or missing filter parts; and fears that the filter would not be effective against cholera. In addition, 17 BSF field studies were reviewed to identify common issues impacting usage. Culturally appropriate technologies and education materials explaining proper maintenance and operation are essential for improved filter performance and sustainability. For Haiti, education materials should be provided in Creole and French and should include, (1) diagrams and descriptions of how the BSF works, (2) how to troubleshoot common problems, (3) how to properly maintain filters, and (4) a contact in case of questions. Operational problems can be minimized by providing long-term technical support, periodic water quality monitoring, and maintenance assistance for filter users.
The presence/absence hydrogen sulphide test (P/A H2S) is widely used as a low-cost alternative faecal indicator test in remote and resource-poor settings. The aim of the paper is to assess how bacterial density and sample volume affect its accuracy. Based on a systematic search, we identified studies that tested water samples (n = 2,034) using both the P/A H2S test and recognised tests for thermotolerant coliforms (TTC) or Escherichia coli. We calculated P/A H2S test specificity and sensitivity against a range of TTC and E. coli densities. For two studies, we compared this with sensitivity and specificity estimates for simulated 100 and 20 ml presence/absence tests. For most of the 19 included studies, as the threshold used to define contamination increased from 1 to 100 cfu/100 ml, P/A H2S test sensitivity increased but specificity decreased. Similarly, the simulation indicated that increasing test volumes from 20 to 100 ml increased sensitivity but reduced specificity. There was potential for bias, for example from lack of blinding during test interpretation, in most of the studies reviewed. In assessing the P/A H2S test as an alternative to standard methods, careful consideration of likely indicator bacteria levels and sample volume is required.
Since the outbreak of cholera in Peru in January 1991, the disease has spread to other Latin-American countries and on several occasions has been imported into the United States. In order to assess the risk of transmission of cholera by water in the United States, an ad hoc committee from the Centers for Disease Control (CDC) and the US Environmental Protection Agency (USEPA) prepared a report (on which this article is based) on the etiology of cholera, the history of outbreaks, symptoms and treatment, transmission and survival, analysis of clinical and water specimens, and prevention of epidemics through water treatment and monitoring. The report also describes the steps that have been taken by CDC and USEPA in South America and recommends future action. Desde el ataque de la epidemia del cólera en El Perú en enero de 1991, esta enfermedad se ha expandido a otros países suramericanos, México, y los EEUU. Para determinar el riesgo de la trasmisión de la cólera por medio del agua en los EEUU, un comité espontáneo de los Centros de Control de Enfermedades (CDC) y la Agencia Protectora del Ambiente de los EEUU (USEPA) prepararon un informe (en el cual está basado este artículo) sobre la etiología de la cólera, la historia de las epidemias, los síntomas y su tratamiento, trasmisión y supervivencia, análisis de especímenes clínicos y de aguas, y la prevención de epidemias con el tratamiento del agua y el monitoreo. El informe también describe los pasos que han sido tornados por el CDC y el USEPA en Sur América y recomienda medidas para el futuro.
After a half century in which new slow sand filtration systems were not built in the United States, this technology has seen a strong revival since the 1980's. Early decisions of three New England communities to choose this technology are examined to identify factors which impede innovation, and how they were overcome. Local leaders want near certainty that a new system will work as planned, leading most to favor technologies which are "proven" through successful operation within the region. Innovative operators in these communities used a credible outside expert who had conducted and disseminated detailed research on this technology to carry out properly designed on-site pilot testing. The resulting performance data satisfied state regulators and local skeptics that the technology would be reliable in the proposed location, and the expert followed through by working closely with communities, plant operators, and consulting engineers as they decided on, designed, and built the early new plants.
Examples of inappropriate technology in developing countries abound. Rather than transferring technology from the industrialized world to the developing world, engineers from the industrialized world might well learn something of the simplified practices that have been found satisfactory in the developing world. These simplified technologies are often appropriate to the local situation and give considerably more promise for successful operation and maintenance. This paper explores some of the technology appropriate to the developing world which should be part of the armamentarium of engineers who would practice in Asia, Africa, and Latin America. Two technologies are selected for discussion; namely self-backwashing declining rate filters; and natural coagulants and coagulant aids. These serve as illustrative examples of the kinds of treatment which are practical for communities in developing countries.
For the past years, use of chlorine has been the preferred method of treating drinking-water. Chlorine may be an effective disinfectant against many pathogenic microorganisms, however its use creates other problems. A better alternative to this approach is the use of biofilm systems. In particular, this modified filtration process offers a reliable, economic alternative to large doses of chlorine for drinking-water utilities.
There is a renewed interest in the assessment of some of the traditional domestic water purification methods and popular devices as well as development/testing of simple low-cost devices. This paper reviews the available information about the efficiency and application of the traditional domestic water purification method employing natural coagulants (seeds of Moringa oleifera and Strychnos potatorum) and laboratory data on the efficiency of domestic candle filters which are popular in urban areas. It also focuses on recent development/testing/modification of a low-cost household filtration system and development/testing of filtration/adsorption media for domestic water filters. -from Authors
Since the outbreak of cholera in Peru in January 1991, the disease has spread to other Latin-American countries and on several occasions has been imported into the United States. In order to assess the risk of transmission of cholera by water in the United States, an ad hoc committee from the Centers for Disease Control (CDC) and the US Environmental Protection Agency (USEPA) prepared a report (on which this article is based) on the etiology of cholera, the history of outbreaks, symptoms and treatment, transmission and survival, analysis of clinical and water specimens, and prevention of epidemics through water treatment and monitoring. The report also describes the steps that have been taken by CDC and USEPA in South America and recommends future action.
by 'Amer Mohamad' Adnan Khayyat.