Biosand Filter

Compiled by:
Bipin Dangol (Environment and Public Health Organization, ENPHO), Dorothee Spuhler (seecon international gmbh)

Executive Summary

The biosand filter (BSF) is a simple household water treatment device, which is an innovation on traditional slow sand filters specifically designed for intermittent use. A BSF consists of a concrete or plastic container filled with specially selected and prepared sand and gravel. As water flows through the filter, physical straining removes pathogens, iron, turbidity and manganese from drinking water. A shallow layer of water sits atop the sand and a biofilm (Schmutzdecke) develops. The biofilm contributes to the removal of pathogens due to predation and competition for food of non-harmful microorganisms contained in the biofilm and the harmful organisms in the water.
In Out

Freshwater

Drinking Water

Introduction

CAWST 2009b Biosand Filter

Biosand filter components. Source: CAWST (2009)

The biosand filter is an innovation on traditional slow sand water filters (which have been used for community water treatment for hundreds of years CAWST 2009), specifically designed for intermittent or household use. The BSFs was developed by Dr. David Manz in the 1990s at University of Calgary, Canada. The filter is simple to use and can be produced locally anywhere in the world because it is built using materials that are readily available. Their capital costs depend on the local material and labour costs. However, they require no consumables and the operating costs are negligible.
BSFs consist of a simple container with a lid, enclosing layers of sand and gravel, which traps physically sediments, pathogens and other impurities from the water. A biofilm, which forms as a shallow layer of water, sits atop the sand column and contributes to the elimination of pathogens.

How Does it Work?

 ENPHO

Family in Jhapa, Nepal using a concrete biosand filter to treat drinking water. Source: ENPHO

The filter container can be made of concrete, plastic or any other water-proof, rust-proof and non-toxic material. The most widely used version is however the concrete container, approximately 0.9 m tall and with a surface of 0.3 m2 (LANTAGNE et al. 2006). The concrete filter box is cast from a steel mould or made with a pre-fabricated pipe (CAWST 2009). The container is filled with layers of sieved and washed sand and gravel, also referred to as filter media (CAWST 2009). There is a standing water height of 5 cm above the sand layer, which is maintained by adjusting the height of the outlet pipe (LANTAGNE et al. 2006; CAWST 2009). It is this design feature that allows the formation of a biofilm layer and distinguishes the BSF from other slow sand filters, allowing for small-scale construction and intermittent use (http://www.cawst.org/en/resources/biosand-filter). A diffusion layer avoids that water reaches the sand surface too fast, which could disturb the biofilm layer.
The filter operation is very simple. Water is poured onto the top of the filter as needed. Then the water will travel slowly through the sand and gravel bed. At the base of the filter the water is collected in a pipe and is drained through plastic piping out of the filter for be collected and stored in a clean water container. Concrete filters have the outlet pipe embedded in the concrete, protecting it against breaks and leaks (CAWST 2009).
The treated water should be collected by the user in a safe storage container placed on a block or stand, so that the container opening is just under the outlet, minimising the risk for recontamination (CAWST 2009).

Plastic version of biosand filter connected to traditional water storage recipient (canari). Source: left: WORLD NEWS INC. (n.y.); right: HYDRAID (n.y.)

Pathogens and suspended solids are removed through a combination of biological and physical processes that take place in the biofilm layer and within the sand layer. These processes include mechanical trapping, predation, adsorption, and natural death (NGAI et al. 2007; EAWAG/SANDEC 2008; CAWST 2009).

 

  • Mechanical trapping and sieving: Suspended solids and pathogens are physically trapped in the spaces between the sand grains.
  • Adsorption and attachment: Pathogens become attached to each other (and thus more easily sieved), suspended solids in the water, and the sand grains.
  • Predation: Pathogens are consumed by other microorganisms in the biological layer. This biological layer matures over one to three weeks, depending on volume of water put through the filter and the amount of nutrients and micro-organisms in the water.
  • Natural death: Pathogens finish their life cycle or die because there is not enough food or oxygen for them to survive.

 

Effectiveness

The biosand Filter is a proven technology, which removes pathogens such as bacteria, protozoa and helminth. BSFs are also somewhat effective for the removal of virus (CAWST 2009). Physical parameters such as turbidity and iron are also eliminated from drinking water. However, dissolved chemicals (such as organic pesticides or arsenic) are not removed. The treated water generally has an agreeable colour, taste and odour.
The table below shows the biosand filter treatment efficiency in removing pathogens, turbidity and iron (adapted form CAWST 2009).

 

 

Bacteria

Viruses

Protozoa

Turbidity

Iron

Laboratory

Up to 96.5%

(BUZUNIS 1995; Baumgartner 2006)

70 to >99%

(Stauber et al. 2006)

>99.9%

(Palmateer et al.1997)

95%

(BUZUNIS 1995);

Not available

Field

87.9 to98.5%

(Earwaker 2006; Duke & Baker 2005)

Not

available

Not

available

85%

(Duke & Baker 2005)

90-95%

(NGAI et al. 2004)

Health impact studies estimate a 30 to 47% reduction in diarrhoea among all age groups, including children under the age of five, an especially vulnerable population group. Source: SOBSEY (2007); STAUBER et al. (2007)

Operation & Maintenance

The flow rate through the filter will slow down over time as the pore openings between the sand grains become clogged. For turbidity levels greater than 50 NTU (Nephelometric Turbidity Units), the water should first be strained through a cloth or sedimented before using the BSF (CAWST 2009).
When the flow rate drops to a level that is inadequate for the household use the filter needs to be cleaned. This is done by a simple ‘swirl and dump’ procedure performed on the top of the sand, and only takes a few minutes (CAWST 2009). The swirl and dump process consist in agitating the surface sand, thereby suspending captured material in the standing layer of the water (http://www.cawst.org/en/resources/biosand-filter). The dirty water is than removed and dumped away. The process can be repeated as many times as necessary to regain the desired flow rate. The need for cleaning depends on the amount and quality of water being put through the filter. If the water is relatively clean (turbidity less than 30 NTU), the filter can likely run for several months without this maintenance procedure (http://www.cawst.org/en/resources/biosand-filter).
When a BSF is used for the first time, there is no biofilm yet. The biological layer typically takes 20 to 30 days to develop to maturity in a new filter depending on inlet water quality and usage (CAWST 2009; http://www.cawst.org/en/resources/biosand-filter). Removal efficiency and the subsequent effectiveness of the filter increase throughout this period.
After cleaning, a re-establishment of the biological layer takes place, quickly returning removal efficiency to its previous level.

Applicability

BSF are suitable for the treatment of water at household-, school- or community-level. BSF can efficiently and directly treat contaminated surface or ground water since it also removes turbidity and iron. However, it is recommended not to use water with turbidity more than 50 NTU. Further, dissolved chemicals (e.g. organic pesticides or arsenic) are not removed.
Chlorinated water should not be poured into this filter as chlorine kills microorganisms presented in biofilm resulting in low pathogen removal performance. Nevertheless, the water can be chlorinated after filtration in order to improve the security for elderly or infant members of the household/community.
A BSF should be constructed only by trained technicians. Though the construction and installation look very simple, incorrect filter design and installation can lead to poor filter performance. However, materials are generally locally available and the construction by trained local staff may create opportunities for local business.
 

Advantages

  • High removal of pathogens
  • Removal of turbidity, colour, odour and iron (water tastes and looks good)
  • Relatively high flow-rates can be achieved (over 30 L per hour)
  • One-time installation with few maintenance requirements and negligible operation costs
  • Long life
  • Can be fabricated from locally available materials generating an opportunity for local businesses
  • Easy to operate and maintain

Disadvantages

  • Biological layer takes 2o to 30 days to develop to maturity
  • Low rate of virus inactivation
  • High turbidity (> 50 NTU) will cause filter to clog and requires more maintenance
  • Requires that the filter be used on a regular basis
  • Cannot remove dissolved compounds
  • Can be difficult to move or transport (due to weight)
  • Lack of residual protection (risk of re-contamination)
  • Requires that the filter be used on a regular basis

References Library

BUZUNIS, B. (1995): Intermittently Operated Slow Sand Filtration: A New Water Treatment Process. Calgary: University of Calgary.

BAUMGARTNER, J. (2006): The Effect of User Behaviour on the Performance of Two Household Water Filtration Systems. (= Masters Thesis). Boston, Massachusetts: Harvard School of Public Health.

BODENNER, J. (2005): BioSandWater Filter. (PDF Presentation). Rockford: Rockford MI Rotary Club. PDF

CAWST (Editor) (2009): Biosand Filter Manual, Design, Construction, Installation, Operation and Maintenance. Alberta: Center for Affordable Water and Sanitation Technology (CAWST). URL [Accessed: 07.04.2010]. PDF

DUKE, W.; BAKER, D. (2005): The Use and Performance of the Biosand Filter in the Artibonite Valley of Haiti: A Field Study of 107 Households. Victoria: University of Victoria. URL [Accessed: 01.01.1970]. PDF

EARWAKER, P. (2006): Evaluation of Household Biosand Filters in Ethiopia. (= Master Thesis). Silsoe: Cranfield University. PDF

ELLIOTT, M.; STAUBER, C.; KOKSAL, F.; DIGIANO, F.; SOBSEY, M. (2008): Reductions of E. coli, Echovirus type 12 and Bacteriophages in an Intermittently Operated Household Scale Slow Sand Filter. In: Water Research 42, 2662-2670. URL [Accessed: 18.01.2011]. PDF

LANTAGNE, D. S.; QUICK, R.; MINTZ, E.D. (2006): Household Water Treatment and Safe Storage Options in Developing Countries. Review of Current Implementation Practices. In: Woodrow Wilson International Center for Scholars (2006): Water Stories: Expanding: Opportunities in small-scale Water and Sanitation Projects, 17-38. URL [Accessed: 18.01.2011]. PDF

NGAI, T.; MURCOTT, S.; SHRESTHA, R. (2004): Kanchan Arsenic Filter (KAF) - Research and Implementation of an Appropriate Drinking Water Solution for Rural Nepal. Cambridge, MA and Kathmandu: Massachusetts Institute of Technology and ENPHO, Nepal. URL [Accessed: 07.04.2010]. PDF

NGAI, T.K.; ROSHAN, R.R.; DANGOL, B.; MAHARJAN, M.; MURCOT; SUSAN (2007): Design for Sustainable Development – Household Drinking Water Filter for Arsenic and Pathogen Treatment in Nepal. In: Journal of Environmental Science and Health Part A 42, 1879–1888.

PALMATEER, G.; MANZ, D.; JURKOVIC, A.; McINNIS, R.; UNGER, S.; KWAN, K. K.; DUDKA, B. (1997): Toxicant and Parasite Challenge of Manz Intermittent Slow Sand Filter. (= Environmental Toxicology, 217/14). John Wiley & Sons, Inc.. URL [Accessed: 07.04.2010]. PDF

SOBSEY, M. (2007): UNC Health Impact Study in Cambodia. Cambodia: University of Cambodia.

STAUBER, C. (2007): The Microbiological and Health Impact of the Biosand Filter in the Dominican Republic. A Randomized Controlled Trial in Bonao. (= PhD). North Carolina: University of North Carolina. URL [Accessed: 18.01.2011]. PDF

STAUBER, C.; ELLIOT, M.; KOKSAL, F.; ORTIZ, G.; LIANG, K.; DIGIANO, F.; SOBSEY, M. (2006): Characterization of the Biosand Filter for Microbial Reductions Under Controlled Laboratory and Field Use Conditions. Water Science and Technology.

HYDRAID (Editor) (n.y.): BioSand Water Filter. USA: Hydraid. URL [Accessed: 14.05.2012].

WORLD NEWS INC. (Editor) (n.y.): The BioSand Water Filter. London UK: World News Inc.. URL [Accessed: 14.05.2012].

CAWST (Editor) (2009): Biosand Filter Manual, Design, Construction, Installation, Operation and Maintenance. Alberta: Center for Affordable Water and Sanitation Technology (CAWST). URL [Accessed: 07.04.2010]. PDF

EAWAG/SANDEC (Editor) (2008): Household Water Treatment and Safe Storage (HWTS). Lecture Notes. (= Sandec Training Tool 1.0, Module 3). Duebendorf: Swiss Federal Institute of Aquatic Science (EAWAG), Department of Water and Sanitation in Developing Countries (SANDEC). URL [Accessed: 08.04.2010]. PDF

Further Readings Library

Reference icon

BODENNER, J. (2005): BioSandWater Filter. (PDF Presentation). Rockford: Rockford MI Rotary Club. PDF

PDF presentation focuses on the sustainable implementation and scaling up of Biosand filters.


Reference icon

DUKE, W.; NORDIN, R.; MAZUMDER, A. (n.y.): Comparative Analysis of the Filtron and Biosand Water Filters. University of Victoria. PDF

Comparative study on performance of the filtron ceramic filter and Biosand filters. Different parameters like turbidity, TOC, DOC, E. coli and total coliform were studied.


Reference icon

LANTAGNE, D. S.; QUICK, R.; MINTZ, E.D. (2006): Household Water Treatment and Safe Storage Options in Developing Countries. Review of Current Implementation Practices. In: ECSP (Editor) (2006): Water Stories: Expanding Opportunities in small-scale Water and Sanitation Projects. Washington D.C., 17-38. URL [Accessed: 06.04.2010]. PDF

Summary and brief evaluation of main household water treatment and safe storage (HWTS) options for developing countries. Options described are: chlorination, biosand filtration, ceramic filtration, solar disinfection, filtration and chlorination, flocculation and chlorination.


Reference icon

MANZ, D.H. (2004): Biosand Water Filter Technology Household Concrete Design. www.manzwaterinfo.ca/. URL [Accessed: 08.04.2010]. PDF

The purpose of this paper is to describe the development, knowledge and the present design of the concrete household biosand water filter in a manner easily understood by readers who may or may not have advanced training in water treatment engineering.


Reference icon

NGAI, T.; MURCOTT, S.; SHRESTHA, R. (2004): Kanchan Arsenic Filter (KAF) - Research and Implementation of an Appropriate Drinking Water Solution for Rural Nepal. Cambridge, MA and Kathmandu: Massachusetts Institute of Technology and ENPHO, Nepal. URL [Accessed: 07.04.2010]. PDF

This paper describes the World Bank DM2003 award, and the plan to implement the KAF (Kanchan Arsenic Filter) project throughout the Terai region in Nepal. The objectives of this project include the establishment of local entrepreneurs for a financially sustainable distribution mechanism, the capacity-building of local people towards long-term, user-participatory safe water provision, the dissemination of KAF information from a central technology centre, as well as networking with other water supply implementers.


Reference icon

NWP (Editor) (2010): Smart Disinfection Solutions. Examples of small-scale disinfection products for safe drinking water. (= Smart water solutions). Amsterdam: KIT Publishers. URL [Accessed: 07.07.2010]. PDF

This booklet, part of the Smart Water Solutions series provides a wide range of methods and products for home water treatment in rural areas.


Reference icon

PALMATEER, G.; MANZ, D.; JURKOVIC, A.; McINNIS, R.; UNGER, S.; KWAN, K. K.; DUDKA, B. (1997): Toxicant and Parasite Challenge of Manz Intermittent Slow Sand Filter. (= Environmental Toxicology, 217/14). John Wiley & Sons, Inc.. URL [Accessed: 07.04.2010]. PDF

Study on removal of parasitic cysts and toxicants as well as bacteria by biosand filter.


Reference icon

YUNG, K. (2003): Biosand Filtration: Application in the Developing World. Waterloo: University of Waterloo. URL [Accessed: 14.05.2012]. PDF

Investigation on current issues that affect the implementation of biosand filter in the developing world.


Reference icon

UNEP (Editor) (1998): Source Book of Alternative Technologies for Freshwater Augmentation in Latin America and the Caribbean. Nairobi: United Nations Environment Programme (UNEP). URL [Accessed: 17.10.2011].

The Latin American and Caribbean countries have seen growing pressure on water resources, with increasing demand and costs, for agricultural, domestic and industrial consumption. This has brought about the need to maximize and augment the use of existing or unexploited sources of freshwater. There are many modern and traditional alternative technologies for improving the utility and augmenting the supply of water being employed in various countries, but with limited application elsewhere due to the lack of information transfer among water resources managers and planners. This book was prepared to provide water resource managers and planners, especially in developing countries and in countries with economies in transition, with information on the range of technologies that have been developed and used in the various countries throughout the world.


Reference icon

DESILLE, D. (2013): Conservation et Traitement de l Eau a Domicile. Paris: Programme Solidarite Eau (PSeau). URL [Accessed: 06.06.2013]. PDF

This practical guide provides a review of different processing techniques and adequate water conservation at home and is structured around 10 key questions that should be posed before choosing a suitable solution.


Case Studies Library

Reference icon

WSP (Editor) (2010): Use of Biosand Filters in Cambodia. Improving Household Drinking Water Quality. Washington D.C.: Water and Sanitation Program (WSP). URL [Accessed: 20.02.2012]. PDF

Well-illustrated case study on the use of biosand filters in Cambodia.


Reference icon

DUKE, W.; BAKER, D. (2005): The Use and Performance of the Biosand Filter in the Artibonite Valley of Haiti: A Field Study of 107 Households. Victoria: University of Victoria. URL [Accessed: 01.01.1970]. PDF

A field study to evaluate the use and performance of Biosand filters at the Artibonite Valley of Haiti. They found it as an attractive option for supplying safe water in rural areas of poorly developed countries with producing water in safe range in 97% of the cases


Reference icon

LEE, T.L. (2001): Biosand Household Water Filter Projects in Nepal. (= (Master Thesis)). Toronto: University of Toronto. URL [Accessed: 08.04.2010]. PDF

Investigation on effectiveness and performance of biosand filters in Nepal.


Reference icon

STAUBER, C.E.; ELLIOTT, M.A.; KOKSAL, F.; ORTIZ, G.M.; DIGIANO, F.A.; SOBSEY, M.D. (2006): Characterisation of the Biosand Filter for E. Coli Reductions from Household Drinking Water under Controlled Laboratory and Field Use Conditions. (= Water and Science & Technology , 3/54). IWA. PDF

This study provides results of laboratory and field studies on removal of E. coli by biosand filter. Field analysis was conducted on 55 household filter near Bonao, Dominican Republic.


Reference icon

STAUBER, C.; ORTIZ, G.; LOOMIS, D.; SOBSEY, M. (2009): A Randomized Controlled Trial of the Concrete Biosand Filter and Its Impact on Diarrhoeal Disease in Bonao, Dominican Republic. The American Society of Tropical Medicine and Hygiene. PDF

This research provide information on ability of Bio-sand filters to improve water quality and to reduce diarrhoeal disease in user compared with non-user households in a randomized controlled trial in Bonao, Dominican Republic, during 2005–2006.


Awareness Raising Material Library

Reference icon

CAWST (Editor) (2009): Biosand Filter. Factsheet. (= Household Water Treatment and Safe Storage Fact Sheet - Academic). Alberta: Center for Affordable Water and Sanitation Technology (CAWST). URL [Accessed: 01.04.2010]. PDF

Extensive factsheet on the principles, construction, operation and maintenance of ceramic candle filters for drinking water treatment.


Training Material Library

Reference icon

CAWST (Editor) (2009): Biosand Filter Manual, Design, Construction, Installation, Operation and Maintenance. Alberta: Center for Affordable Water and Sanitation Technology (CAWST). URL [Accessed: 07.04.2010]. PDF

This training manual provides overview on biosand filters including construction, installation, operation and maintenance of BSF.


Reference icon

CAWST (Editor) (2009): Biosand Filter. Factsheet. (= Household Water Treatment and Safe Storage Fact Sheet - Academic). Alberta: Center for Affordable Water and Sanitation Technology (CAWST). URL [Accessed: 01.04.2010]. PDF

Extensive factsheet on the principles, construction, operation and maintenance of ceramic candle filters for drinking water treatment.


Reference icon

EAWAG/SANDEC (Editor) (2008): Household Water Treatment and Safe Storage (HWTS). Lecture Notes. (= Sandec Training Tool 1.0, Module 3). Duebendorf: Swiss Federal Institute of Aquatic Science (EAWAG), Department of Water and Sanitation in Developing Countries (SANDEC). URL [Accessed: 08.04.2010]. PDF

Lecture notes on the technical and non-technical aspects of sanitation household-level drinking water treatment and safe storage (HWTS) in developing countries.


Reference icon

EAWAG/SANDEC (Editor) (2008): Household Water Treatment and Safe Storage (HWTS). Presentation. (= Sandec Training Tool 1.0, Module 3). Duebendorf: Swiss Federal Institute of Aquatic Science (EAWAG), Department of Water and Sanitation in Developing Countries (SANDEC). URL [Accessed: 18.02.2011].

Presentation on the technical and non-technical aspects of sanitation household-level drinking water treatment and safe storage (HWTS) in developing countries.


Important Weblinks