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Household water treatment and safe storage

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Household or point of use drinking water treatment and safe storage (HWTS) provides a means to improve the quality of their water by treating it in the home. These technologies have been shown to improve the microbiological and, in some cases, the chemical quality of drinking water and to reduce diarrheal disease.

Description: 

Ideally, piped drinking water supplies incorporating source water protection and centralized treatment would be available to all. However, nearly one-billion people worldwide do not have access to an “improved” source of drinking water, and many improved sources are unsafe and some distance from the home (UN, 2008; Godfrey et al., 2009). Despite the eventual goal of providing a safe, sustainable supply of drinking water at home to all people, the World Health Organization (WHO) and other international bodies have recognized the benefit of targeted, interim approaches for those with unsafe drinking water (Clasen, 2009).

Household or point of use (POU), drinking water treatment and safe storage provides a means to improve the quality of their water by treating it in the home. Popular treatment technologies include chemical disinfectants, coagulants, ceramic filters, biological sand filters, solar disinfection (SODIS) or ultraviolet disinfection processes, and combined products with both coagulant and disinfectant (e.g. Procter & Gamble PUR product) (Clasen, 2009; Sobsey, 2002). These technologies have been shown to improve the microbiological and, in some cases, the chemical quality of drinking water and to reduce diarrheal disease (Sobsey et al., 2008; Clasen et al., 2006; Fewtrell et al., 2005). Four of the most widely promoted technologies are shown in Figure 1.

illustration © climatetechwiki.org

Figure 1: Four popular POU technologies. On the left two POU filters with descriptions of the individual elements; the ceramic water purifier and a concrete biosand water filter (BSF). Both of the devices pictured stand between 0.5-1 meter high. Second from the right is a photo of bottles used for solar disinfection (SODIS). On the far right is an image of a Procter & Gamble PUR coagulation/chlorination packet; an individual packets contains 4 g of crystals and can be used to treat 10 liters of water.

An analysis of the potential for long-term sustained-use of the technologies that have been most widely promoted by the WHO Network to Promote Household Drinking Water Treatment and Safe Storage (HWTS Network) has been conducted. The results are summarized in figure 2.

illustration © climatetechwiki.org

Figure 2: Scoring of popular point-of-use drinking water treatment technologies based on sustainability criteria. Higher numbers indicate better scores. (source/further details: Sobsey et al., 2008)

In addition to these, HWTS products manufactured by large companies have become popular in both developed countries and emerging economies. These faucet and pitcher format products include the Procter & Gamble line of PUR filtration systems, Brita filters, and others. Recently introduced commercial products for emerging economies include the Hindustan Unilever Pureit and the Tata Swach filter lines; both filters are meant to sit on a table-top or counter-top, do not require electricity or running water, and have an incorporated safe storage vessel (figure 3).

illustration © climatetechwiki.org

Figure 3: The Pureit (on the left) can be used to treat about 1500 liters of water (depending on the model) using a carbon block to absorb and filter impurities, followed by chlorine disinfection; replacement of the chlorine unit enables treatment of 1500 liters more. The Tata Swach (on the right) uses rice husk ash and silver to treat water; it enables treatment of up to 3000 liters before the so-called treatment “bulb” must be replaced.

New HWTS Technologies continue to emerge. The most current review of HWTS devices available worldwide was released by Program for Appropriate Technology in Health (PATH) in 2010. It includes qualitative assessments of treatment efficacy, health impact, safety, cost, acceptability, sustained use, supply chain and other factors for 19 popular technologies and eight promising devices still in research and development. The table from the PATH report is too large to reproduce in this article, but it is freely available online (PATH, 2010).

Household treatment of drinking water by heating, usually to the point of boiling, has been practiced in many societies for millennia and is far more widely practiced than all of the above HWTS methods combined (Clasen, 2009). It is highly effective at eliminating all classes of pathogens. However, boiling has numerous disadvantages and has not been generally promoted by HWTS practitioners. Among these disadvantages are the time to gather fuel, the sometimes prohibitive costs, and the degradation of indoor air quality that leads to increased health hazards including respiratory infections. Despite these, there have been recent calls to re-examine the costs and benefits of boiling and to optimize the process (Clasen et al., 2008).

HWTS has become an increasingly promoted technical options in the international health community since the introduction of the Safe Water System by the US Centers for Disease Control and Prevention in 1992 (CDC, no date). The formation of the WHO HWTS Network in 2003 established the major community of practice for researchers, implementers, and advocates of HWTS (WHO, 2010a).

This article focuses on HWTS as an adaptation strategy for climate change. Therefore, the emphasis is on long-term adoption and scale-up. The principles of HWTS implementation in an emergency or natural disaster setting are fundamentally different. For guidance on HWTS in emergency situations, resources are included in the references (Lantagne and Clasen, 2009; International Federation of Red Cross and Red Crescent Societies, 2008).

Advantages of the technology top

Degradation of water quality is expected to be one of the key impacts of climate change on water resources and water supply. Projected increases in flooding, drought, decreasing water availability, algal blooms, coastal inundation, and sea level rise have both direct and indirect effects on drinking water quality (Kundzewicz et al., 2007; WHO and DFID, 2010). Direct effects occur through transport of fecal and other wastes into water supplies, growth of harmful algal blooms, for example. Indirect effects on drinking water quality occur when users are forced to switch to lower quality drinking water supplies, for example when groundwater tables decline and users must switch to contaminated surface water. HWTS increases resilience to water quality degradation by enabling users to improve water quality at the point of use.

It is estimated that there were 18.8 million users of HWTS devices worldwide in 2007, with rapid growth of roughly 25% per year. The growth rate may have increased even further in recent years with the introduction and popularization of Hindustan Unilever, Tata and other HWTS products targeted to the Indian middleclass (see Figure 6). In addition to these HWTS users, 350 million people were estimated to boil water for household consumption from a survey of 58 low-income countries. Not included in this number were China, Indonesia and other large countries in which boiling is common (Clasen, 2009).

Diarrheal disease can be a key component of the “poverty trap” that hinders development by decreasing economic productivity (Bonds et al., 2009). Preventing waterborne disease can lead to increased school attendance, more time spent in gainful activities and childcare, and less diversion of limited financial resources to pay for medical care. POU disinfection was the least expensive intervention reviewed in a World Health Organization (WHO) analysis of the costs and benefits of improved water and sanitation, resulting in a benefit-to-cost ratio of between $5-and-$60 per $1 invested (Hutton and Haller, 2004).

Financial requirements and costs top

Both capital and ongoing costs must be taken into account when considering the appropriateness of an HWTS implementation program for a given community. Some technologies (e.g chemical disinfectants) have few if any capital costs but must be purchased periodically; others (e.g. biosand filters) have relatively large up-front costs with little or no on-going costs.

The costs associated with training and educating users will exceed all costs associated with the HWTS “hardware.” One example is solar disinfection (SODIS). In many settings, SODIS can be practiced with negligible costs, either capital or on-going. However, uptake and sustained use cannot be achieved without significant investment in training and education. Regardless of the technology, attempting to implement HWTS programs without a substantial education component is likely to decrease the long-term sustainability and impact.

Many HWTS implementation programs are donor-driven, offering partial or complete subsidization of product costs. Donor-driven HWTS programs have been successful in some settings, particularly in refugee camps, following natural disasters and during waterborne disease outbreaks. Targeted subsidization can be used to establish products in a market. However, subsidized HWTS programs can distort the market and undermine long-term efforts to reach scale (Vousvouras and Heierli, 2010; Osborn and HOlstag; 2010). Arguments for and against subsidization are addressed in a 2006 report by the Massachusetts Institute of Technology (MIT) (Murcott, 2006).

Full cost recovery approaches provide the greatest potential for reaching scale. Recent studies focusing on full cost recovery and market mechanisms to scale-up HWTS are available (Kols, 2010; Harris, 2005; Heierli, 2008; Kols, 2009). In some settings, social marketing approaches can be effective (POUZN Project, 2007).

Institutional and organisational requirements top

Correct, sustained use of HWTS is necessary to achieve long-term impact on user health. Although HWTS devices are generally designed to be easy to operate and maintain, the complexity of design, and the durability, operation and maintenance requirements vary. Additionally, some HWTS technologies (e.g. chemical disinfectants) are consumable and need to be replaced frequently. Although research on the factors affecting use rates of HWTS is evolving, most evidence indicates that durable technologies (e.g. filters) that do not include consumable components achieve higher rates of sustained use following implementation (Sobsey et al., 2008; Hunter, 2009).

Fact sheets and other concise implementation tools for HWTS devices and programs have been generated by HWTS Network members. These provide simple summaries of the research, best practices, training tools, and lessons learned from implementation for many popular HWTS devices. Many of these are linked from a page dedicated to “Fact sheets and tools” on the HWTS Network website (WHO, 2010b).

HWTS is a technology that is fundamentally operated and managed in the household; therefore, there are few if any institutional or organizational requirements for users. However, scaling up HWTS has proven a challenge. A WHO report examines the state of HWTS globally and presents ten key recommendations for scaling up (listed below) that are discussed in greater detail in the report (Clasen, 2009).

  1. Focus on the users.
  2. Develop and use partners.
  3. Improve and expand on boiling.
  4. Continue to pursue non-commercial strategies.
  5. Continue to pursue market-driven strategies.
  6. Leverage existing local strengths.
  7. Initiate and use relevant, practical research.
  8. Overcome public policy barriers to advancing HWTS.
  9. Engage national and regional governments.
  10. Engage international leadership to support HWTS.
Opportunities for implementation top

Generally, opportunities for HWTS implementation are greatest when either (1) in the midst of a waterborne disease outbreak or (2) when non-health benefits of HWTS are perceived to be high. HWTS does not provide the key non-health benefit of improved drinking water supply at the home, namely time-savings from not having to fetch water. However, non-health benefits include aesthetic improvement of water quality, cost savings over other water sources (e.g. bottled or vended water), and the social status associated with being able to serve treated drinking water to guests. Marketing HWTS as an “aspirational” product associated with a better lifestyle can improve uptake (POUZN Project, 2007).

Most marketing efforts of consumable HWTS products during non-crisis times have led to modest uptake and sustained use. However, recent evidence suggests that potential consumers that become aware of HWTS products through marketing campaigns will turn to those products when the perceived need is greater (e.g. during a waterborne disease outbreak) (Gately, 2010).

References top

Bonds, M.H., Keenan, D.C., Rohani, P. And Sachs, J.D., (2009) “Poverty trap formed by the ecology of infectious diseases” Proceedings of the Royal Society B: Biological Sciences. 277:1185-1192.

CDC (no date) “Safe Water Systems for the Developing World: A Handbook for Implementing Householdbased Water Treatment and Safe Storage Projects” http://www.cdc.gov/safewater/manual/sws_manual.pdf

Clasen, T. (2009) Scaling Up Household Water Treatment Among Low-Income Populations. (WHO/HSE/ WSH/09.02) World Health Organization, Geneva. http://whqlibdoc.who.int/hq/2009/WHO_HSE_WSH_09.02_eng.pdf

Clasen, T., Roberts, I., Rabie, T., Schmidt, W., & Cairncross, S. (2006). Interventions to improve water quality for preventing diarrhoea. Cochrane Database Syst Rev, 3, CD004794.

Clasen, T.F., Thao, do H., Boisoon, S. and Shipin, O. (2008) Microbiological Effectiveness and Cost of Boiling to Disinfect Drinking Water in Rural Vietnam. Environ. Sci. Technol. 42(12):4255-4260.

Fewtrell, L., Kaufmann, R. B., Kay, D., Enanoria, W., Haller, L., & Colford, J. M., Jr. (2005). Water, sanitation, and hygiene interventions to reduce diarrhoea in less developed countries: a systematic review and meta-analysis. Lancet Infect Dis. 5(1), 42-52.

Gately, M. (2010) “HWTS education: a hidden success in emergency situations” Presentation at the “Water and Health: Where Science Meets Policy” conference. Chapel Hill, USA. October 26, 2010.

Godfrey, S., Labhasetwar, P., Wate, S. and Pimpalkar, S. (2009) “How safe are the global water coverage figures? Case study from Madhya Pradesh, India” Environ Monit Assess DOI 10.1007/s10661-010-1604-3

Harris, J. (2005) Challenges to the Commercial Viability of Point-of-Use (POU) Water Treatment Systems in Low-Income Settings. Master of Science Dissertation. Oxford University. School of Geography and the Environment. http://www.who.int/household_water/research/commercial_viability.pdf

Heierli, U. (2008) Marketing safe water systems: why it is so hard to get safe water to the poor—and so profitable to sell it to the rich. Swiss Agency for Development and Cooperation (SDC). Bern Switzerland. 114 p. http://www.irc.nl/page/46695

Hunter, P.R. (2009) Household Water Treatment in Developing Countries: Comparing Different Intervention Types Using Meta-Regression. Environ. Sci. Technol. 43(23):8991-8997.

Hutton, G. and L. Haller (2004) “Evaluation of the costs and benefits of water and sanitation improvements at the global level” World Health Organization. Geneva. http://www.who.int/water_sanitation_health/wsh0404/en/

International Federation of Red Cross and Red Crescent Societies (2008) Household water treatment and safe storage in emergencies A field manual for Red Cross/Red Crescent personnel and volunteers. http://www.ifrc.org/Docs/pubs/health/water/142100-HWT-en_LR.pdf

Kols, A. (2009) Supply and Demand for Household Water Treatment Products in Andhra Pradesh, Karnataka, and Maharashtra, India. PATH. Seattle. http://www.path.org/files/TS_supply_demand_hwts_india.pdf

Kols, A. (2010) Consumer and Market Research on Household Water Treatment Products in Vietnam. PATH. Seattle. http://www.path.org/files/TS_swp_hwts_viet.pdf

Kundzewicz, Z.W., L.J. Mata, N.W. Arnell, P. Döll, P. Kabat, B. Jiménez, K.A. Miller, T. Oki, Z. Sen and I.A. Shiklomanov (2007) “Freshwater resources and their management. Climate Change 2007: Impacts, Adaptation and Vulnerability.” Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden and C.E. Hanson, Eds., Cambridge University Press, Cambridge, UK, 173-210. http://www.ipcc.ch/publications_and_data/ar4/wg2/en/contents.html

Lantagne, D. and Clasen, T. (2009) Point of Use Water Treatment in Emergency Response. London School of Hygiene and Tropical Medicine. http://www.ehproject.org/PDF/ehkm/lantagne-pou_emergencies2009.pdf

Murcott, S. (2006) Implementation, Critical Factors and Challenges to Scale-Up of Household Drinking Water Treatment and Safe Storage Systems. http://www.hip.watsan.net/page/1738

Osborn, P. and Holstag, H. (2010) “300in6: Safe water for 300 million in 6 years. Massive scaling-up of safe water solutions” Presentation at the “Water and Health: Where Science Meets Policy” conference. Chapel Hill, USA. October 26, 2010. http://300in6.org/wp-content/uploads/2010/10/300in6-at-HWTS-241010-v5-St...

PATH (2010) Global Landscape of Household Water Treatment and Safe Storage Products. Seattle. http://www.path.org/files/TS_swp_hwts_gl.pdf

POUZN Project. (2007) Best Practices in Social Marketing Safe Water Solution for Household Water Treatment: Lessons Learned from Population Services International Field Programs. The Social Marketing Plus for Diarrheal Disease Control: Point-of-Use Water Disinfection and Zinc Treatment (POUZN) Project, Abt Associates Inc., Bethesda, MD. http://www.ehproject.org/PDF/ehkm/LessonsLearnedFinal.pdf

Sobsey, M.D. (2002) Managing water in the home: accelerated health gains from improved water supply, (WHO/SDE/WSH/02.07) World Health Organization, Geneva. http://www.who.int/water_sanitation_health/dwq/wsh0207/en/

Sobsey, M.D., C.E. Stauber, L.M. Casanova, J.M. Brown & M.A. Elliott (2008) Point of Use Household Drinking Water Filtration: A Practical, Effective Solution for Providing Sustained Access to Safe Drinking Water in the Developing World. Environ Sci Technol. 42 (12):4261–4267.

UN (2008) Millennium Development Goals Progress Report. United Nations, New York

Vousvouras, C.A. and Heierli (2010) Safe Water at the Base of the Pyramid. 300in6 Initiative. http://300in6.org/wp-content/uploads/2010/02/Safe-Water-at-the-Base-of-t...

WHO (2010a) Household water treatment and safe storage. http://www.who.int/household_water/network/en/ Accessed October 29, 2010.

WHO (2010b) HWTS Fact sheets and tools. http://www.who.int/household_water/network/tools/en/index.html

WHO and DFID (2010) “Vision 2030: The Resilience of Water Supply and Sanitation in the Face of Climate Change.” http://www.who.int/water_sanitation_health/publications/9789241598422_cd...