Household water treatment

FAQ sheet on household water treatment, prepared by IRC International Water and Sanitation Centre, The Netherlands

Introduction

An estimated 1.1 billion people rely on unsafe drinking-water sources. Even more are likely to be using microbiologically contaminated water if one takes into account re-contamination during water collection and transport, the use of unsafe storage vessels and poor hygiene. Millions of people also face chronic poisoning from naturally occurring chemical pollutants in water, such as arsenic and fluoride. Effective technologies for household water treatment and storage, in combination with improved hygiene behaviour, can help reduce water-related diseases much more quickly than it will take to design and implement piped community water supplies [1].

The focus of this FAQ is on options, suitable for developing countries, for:

1. Treatment of microbiological contamination
2. Treatment of chemical contamination:
   2a. arsenic removal
   2b. fluoride removal

For commercially available treatment systems we refer to NSF International [5].

1. Treatment of microbiological contamination

The prevention of microbiological contamination in water is the measure likely to have the greatest impact, as this is the cause of 2.2 million deaths a year (mostly children) from diarrhoeal disease. Microbiological contamination in water means contamination by disease-causing organisms (pathogens). According to Sobsey [1], the most promising and accessible of the technologies for household water treatment are:

• Filtration with ceramic filters [6]
• Adapted slow sand filter called BioSand filter [9]
• Chlorination with storage in an improved vessel [8]
• Solar disinfection (SODIS) in clear bottles by the combined action of UV radiation and heat [7]
• Thermal disinfection (pasteurisation) in opaque vessels with sunlight from solar cookers or reflectors
• Combination systems employing chemical coagulation-flocculation, sedimentation, filtration and chlorination

Boiling of water is not included because:

• fuel is expensive; fuel consumption leads to environmental degradation (if firewood is used) and (indoor) air pollution; and firewood collection is time consuming
• cultural beliefs and preferences can discourage drinking boiled water: in some cultures boiled water is considered only appropriate for the sick, and people often dislike the flat taste of boiled water

All of the systems listed above have been shown to dramatically improve the microbiological quality of water. During an e-conference in October 2002 on household water security, several experts presented their views and recent experiences with ceramic filters, slow sand filters, solar disinfection and chlorination [11].

2. Treatment of chemical contamination

Chemically contaminated water is defined for the purpose of this FAQ as water that is contaminated by natural sources; that is, chemicals from rocks and soils.

a) Arsenic removal

Arsenic pollution of groundwater is already a major problem in Bangladesh and West Bengal (India), while new serious cases are emerging in Nepal and Bihar (India). Household treatment can be an effective short-term solution until alternative safe water sources are found or central water treatment plants are installed (this includes commercial treatment units set up to deliver bottled drinking water). Domestic treatment systems can also be used as an alternative to centralised arsenic removal, or to supplement such systems. Several websites provide overviews and updates on available arsenic treatment technologies at the household level [ 2, 3,10]. A rapid assessment of household treatment options undertaken in Bangladesh in 2000-2001 identified four acceptable technologies [12]:

• Alcan Enhanced Activated Alumina adsorption to enhanced activated alumina
• Tetrahedron ion exchange
• Sono 3-kolshi method passive coagulation with Fe and/or adsorption to sand matrix
• Stevens Institute method enhanced coagulation and co-precipitation (ferrous sulphate), filtration and adsorption to sand filter

Other emerging technologies include:

• SORAS solar oxidation and removal of arsenic; irradiation of water with sunlight in UV-A transparent bottles [16]
• A filter that uses a ferrous sulfate solution bonded to crushed brick particles [13]

In the long term, leaching of arsenic from sludge (wastes) from treatment units could pose a problem, although disposal of such wastes in cow-dung may help eliminate arsenic [15].

b) Fluoride removal

Fluorosis is endemic in at least 25 countries. It is difficult and expensive to reduce a high natural level of fluoride in water. This means that the first option should be to find an alternative source with lower fluoride levels. If there is no other possible or cost-effective source, defluoridation must be attempted to avoid the toxic effects. The best method depends on local circumstances, fluoride concentration and socio-economic factors. Only the water for drinking and cooking needs to be defluoridated. The entire water demand is often ten times higher, and to defluoridate this would be too expensive, as well as producing a large amount of toxic sludge [14].

The World Health Organization (WHO) has identified and evaluated the most promising defluoridation methods, which can be used at both a central and a household level in developing countries [4]:

• Bone charcoal in 1998, WHO introduced the ICOH enriched charcoal domestic filter in Thailand another countries
• Contact precipitation precipitation based on the addition of calcium and phosphate compounds has so far only been implemented at domestic level in Kenya and Tanzania
• Nalgonda an aluminium sulphate based coagulation-flocculation sedimentation, used in India and Tanzania
• Activated alumina
• Clay clay column defluoridators have been installed in households in Sri Lanka

References

[1] Sobsey, M.D. (2002). Managing water in the home: accelerated health gains from improved water supply [report]. Geneva, Switzerland: World Health Organization (WHO). Retrieved June 21, 2005, from the World Wide Web

This review considers methods and systems to protect water during storage, collection and use that improve microbial quality and thereby reduce pathogen exposure and risks of diarrhoeal and other waterborne diseases. It first discusses appropriate containers for safe household storage of collected water. This is followed by a review of the most promising and accessible household water treatment technologies: filtration with ceramic filters, chlorination with storage in an improved vessel, solar disinfection in clear bottles by the combined action of UV radiation and heat, thermal disinfection (pasteurisation) in opaque vessels with sunlight from solar cookers or reflectors and combination systems employing chemical coagulation-flocculation, sedimentation, filtration and chlorination. Special attention is given to the treatment of turbid (cloudy) water. The need for behavioural, motivational, and economic support for household water treatment is stressed. The Hazard Analysis at Critical Control Points (HACCP) methodology, as part of a Water Safety Plan (WSP), is used to evaluate risks for each type of water storage vessel and treatment system. Summary tables are provided to compare the recommended household treatment technologies and candidate technologies to pre-treat turbid household water.

Contact: Prof. Mark D. Sobsey, Department of Environmental Sciences and Engineering
School of Public Health, University of North Carolina, Chapel Hill, North Carolina 27599-7400, USA
Tel.: +1-919-9667303, fax: +1-919-9664711, e-mail: Mark Sobsey

[2] Water treatment & alternative supplies. West Bengal & Bangladesh Arsenic Crisis Information Centre. [web page]. Retrieved May 15, 2003, from the World Wide Web: http://bicn.com/acic/resources/arsenic-on-the-www/safewater.htm

Provides an overview of resources on: arsenic technology verification; arsenic removal technology providers & projects; alternative water supply technology providers & projects; and field test kits & field test kit verification.

[3] Arsenic remediation technologies: online informational database. Massachusetts Institute of Technology. [web page]. Retrieved June 21, 2005, from the World Wide Web: http://www.mit.edu/people/murcott/arsenic/overview.htm

Provides basic data on performance, cost, applications, contact persons, and references of 50 specific arsenic remediation options, arranged by the following process types: oxidation, coagulation/co-precipitation; sedimentation; filtration; adsorption; ion exchange; membrane/ reverse osmosis; biological; and other.

Contact: Susan Murcott, Lecturer, Dept. of Civil & Environmental Engineering, MIT. E-mail Susan Murcott.

[4] Lennon, M. et.al. (2004). Rolling revision of the WHO guidelines for drinking-water quality : fluoride. [report], draft for review. Geneva, Switzerland: World Health Organization. Retrieved June 21, 2005, from the World Wide Web: http://www.who.int/water_sanitation_health/dwq/nutfluoride.pdf

This draft monograph on fluoride in drinking water for health workers and sanitary engineers focuses on the removal of excessive fluoride. The monograph begins with an overview on fluoride occurrence, geochemistry and exposure, followed by an assessment of human health risks of fluoride, including skeletal and dental fluorosis. It then looks at the beneficial use of fluoride for dental health and briefly discusses the derivation and application of the 1996 World Health Organization (WHO) guideline value (1.5 mg/l) for fluorides in water. The chapter on removal of excessive fluoride introduces the basic characterisation of the removal methods. Then the most promising defluoridation methods are presented, one by one: bone charcoal, contact precipitation, Nalgonda, activated alumina and clay. Finally the methods presented are compared using indicators that may be appropriate in developing countries. The monograph concludes with a summary of water fluoridation practice as applied in central water treatment.

[5] Drinking water treatment units. NSF International. [web page]. Retrieved May 15, 2003, from the World Wide Web: http://www.nsf.org/dwtu/

This page lists relevant standards for point-of-use (POU) and point-of-entry (POE) drinking water treatment units, and gives access to a database on certified drinking water treatment units searchable by manufacturer, contaminant reduction claim, and product standard, model and type. Consumer information on home water treatment units is available at: http://www.nsfconsumer.org/water/dw_treatment.asp

Contact: Craig Zechman, Account Executive for the Drinking Water Treatment Units Program, NSF International, PO Box 130140, Ann Arbor, MI 48113-0140, USA, Tel.: +1-734-7698010, fax: +1- 734-7690109, e-mail: Craig Zechman or e-mail: DWTU

Bibliography and additional reading

[6] Ceramic water purifier (CWP). See under filters at the Potters for Peace web site. [web page]. Retrieved Feb 19, 2007, from the World Wide Web: http://pottersforpeace.org/

Since 1998, Potters for Peace (PFP) has been developing a low-tech, low-cost, colloidal silver-enhanced ceramic water purifier (CWP). Field experience and clinical test results have shown this filter to effectively eliminate approximately 99.88% of most water born disease agents.

Contact: Ron Rivera, International Coordinator, Potters for Peace, Managua, Nicaragua, e-mail: Ron Rivera, web: http://pottersforpeace.org/

[7] Solar water disinfection. SANDEC. [website]. Retrieved May 15, 2003, from the World Wide Web: http://www.sodis.ch/

This site provides information on solar disinfection (SODIS) of drinking water, a simple water treatment method using solar UV-A radiation and temperature to inactivate pathogens causing diarrhoea. The site includes background information, news, project descriptions, online technical notes and educational materials, a bibliography, frequently asked questions, and links. Information is available in English, French, German and Turkish.

Contact: Martin Wegelin, Regula Meierhofer, Swiss Federal Institute for Environmental Science and Technology, Department of Water and Sanitation in Developing Countries (EAWAG/SANDEC), Ueberlandstrasse 133, CH-8600 Duebendorf, Switzerland. Tel.: +41-1-8235019, fax: +41-1-8235399, e-mail: Martin Wegelin, e-mail: Regula Meierhofer

[8] Safe water system. Centers for Disease Control and Prevention (CDC). [webpage]. Retrieved May 15, 2003, from the World Wide Web: http://www.cdc.gov/safewater/

The Safe Water System (SWS) is a household-based intervention to provide safe water developed by the CDC and the Pan American Health Organization (PAHO). The basis of the intervention is: point-of-use treatment using sodium hypochlorite solution purchased locally or produced on-site; safe water storage in plastic containers with a narrow mouth, lid, and a spigot to prevent recontamination; and hygiene promotion. The web page describes project experiences in 16 developing countries, provides brief facts on what is known and still unknown about SWS, includes a handbook on SWS implementation in English and Spanish, articles on SWS in academic journals and abstracts of conference papers on SWS, an 11-minute SWS video (Real Audio format), and related links.

Contact: SWS Program, Foodborne and Diarrheal Diseases Branch, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Mailstop C-14, 1600 Clifton Road, Atlanta, GA 30333, USA, e-mail: safewater

[9] BioSand concrete filter. The Center for Affordable Water and Sanitation Technology (CAWST). [web page]. Retrieved Feb 19, 2007, from the World Wide Web: http://www.cawst.org/index.php?id=128

CAWST claims that the BioSand filter was the most affordable, efficient and easy-to-use of all the household treatment systems they had identified and evaluated. The BioSand filter is a slow sand household water filter, which is specifically designed for intermittent use in developing countries. The filter is a concrete container, enclosing layers of sand and gravel. It uses the same technology as the commercial plastic filters produced by Davnor. BioSand filters have been introduced in more than 30 countries and cost between US$10 and US$30. The web page includes a short technical description of the filter, support studies (accessible only for members who have followed a CAWST training course), a discussion forum, and links to BioSand projects in developing countries.

Contact: Ron Lentz, Center for Affordable Water and Sanitation Technology (CAWST),
920 Rideau Road S.W., Calgary, Alta, Canada, T2S 0R6
Tel.: +1-403-2496681, fax: +1-403-2193373, e-mail: Ron Lentz, website: http://www.cawst.org/
Of special interest is the Biosandfilter.org web site by BushProof, a humanitarian enterprise registered in the UK and Madagascar.

[10] The Arsenic Website Project. Harvard and MIT. [web page]. Retrieved June 21, 2005, from the World Wide Web: http://phys4.harvard.edu/~wilson/arsenic/remediation/arsenic_project_remediation_technology.html

[11] Household water security e-conference and virtual forum: October 14 November 1, 2002. UNICEF, WHO and HTN. [web page]. Retrieved May 15, 2003, from the World Wide Web: http://www.unicef.org/programme/wes/econf.htm

[12] Sunderland, D. [et al.]. Rapid assessment of technologies for arsenic removal at the household level. [conference paper]. In: Ahmed, F. Technologies for Arsenic Removal from Drinking Water: BUET-UNU International Workshop 5 7 May 2001, Dhaka, Bangladesh. Retrieved May 15, 2003, from the World Wide Web: http://www.unu.edu/env/Arsenic/Sutherland.pdf

[13] Arsenic removal: low-cost water filter introduced. In: Source Weekly, no. 29-30, July 2002. [article]. Retrieved May 15, 2003, from the World Wide Web: http://www.irc.nl/page/2083

Contact: Prof. M. Fakhrul Islam, Dept. of Applied Chemistry and Chemical Technology, University of Rajshahi, Rajshahi 6205 Bangladesh, fax: +880-721-750064; Mr David Nunley, IDE-Bangladesh Country Director, IDE-Bangladesh, http://www.ideorg.org [BBC, 14 Jul 2002; Abstracts, 18 Jul 2002, Fifth International Conference on Arsenic Exposure and Health Effects]

[14] Fluoride in water: An overview. [web page]. Unicef, Water Environment and Sanitation. Retrieved May 15, 2003, from the World Wide Web: http://www.unicef.org/programme/wes/info/fluor.htm

[15] Ali, M.A. [et al.] (2003). Fate of arsenic in wastes generated from arsenic removal units. In: Ahmed, F. [et al.]. Fate of arsenic in the environment: BUET-UNU International Symposium, 5-6 February 2003 Dhaka, Bangladesh. Tokyo, Japan: United Nations University. [paper]. Retrieved May 15, 2003, from the World Wide Web: http://www.unu.edu/env/Arsenic/Dhaka2003/12-Ali.pdf

[16] Solar oxidation and removal of arsenic from drinking water (SORAS) [web page]. Swiss Federal Institute for Environmental Science and Technology (EAWAG). Retrieved June 25, 2003, from the World Wide Web: http://www.eawag.ch/news_e/arsenic/oxidation.html

Contact persons

• Prof. M. Fakhrul Islam (arsenic removal), Dept. of Applied Chemistry and Chemical Technology, University of Rajshahi, Rajshahi 6205 Bangladesh, fax: +880-721-750064; Mr David Nunley (arsenic removal), IDE-Bangladesh Country Director, IDE-Bangladesh
• Ron Lentz (BioSand concrete filter), Center for Affordable Water and Sanitation Technology (CAWST),
  920 Rideau Road S.W., Calgary, Alta, Canada, T2S 0R6
  Tel.: +1-403-2496681, fax: +1-403-2193373
• Adriaan Mol, BioSandFilter.org
• Susan Murcott (arsenic remediation technologies), Lecturer, Dept. of Civil & Environmental Engineering, MIT.
• Ron Rivera (ceramic water filter), International Coordinator, Potters for Peace, Managua, Nicaragua
• Safe Water System Program, Foodborne and Diarrheal Diseases Branch, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Mailstop C-14, 1600 Clifton Road, Atlanta, GA 30333, USA
• Prof. Mark D. Sobsey (managing water in the home), Department of Environmental Sciences and Engineering, School of Public Health, University of North Carolina, Chapel Hill, North Carolina 27599-7400, USA
  Tel.: +1-919-9667303, fax: +1-919-9664711
• Martin Wegelin, Regula Meierhofer (solar water disinfection), Swiss Federal Institute for Environmental Science and Technology, Department of Water and Sanitation in Developing Countries (EAWAG/SANDEC), Ueberlandstrasse 133, CH-8600 Duebendorf, Switzerland. Tel.: +41-1-8235019, fax: +41-1-8235399
• Craig Zechman (drinking water treatment units), Account Executive for the Drinking Water Treatment Units Program, NSF International, PO Box 130140, Ann Arbor, MI 48113-0140, USA, Tel.: +1-734-7698010, fax: +1- 734-7690109

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Creation date: 16 May 2003
Revised date : 25 June 2003
Author : Cor Dietvorst, Information Specialist at IRC International Water and Sanitation Centre, Delft, The Netherlands
Peer reviewer: Jo Smet, Senior Professional Officer at IRC International Water and Sanitation Centre, Delft, The Netherlands
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