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Clean drinking water for homes in Africa and other less developed countries
BMJ
2005-09-02
Flocculant-disinfectant treatment with bleach is effective and acceptable. More than 1 billion people in developing countries lack access to safe water, and 2.2 million die annually of diarrhoea.
Unfortunately, communities where diarrhoea is a leading cause of morbidity and mortality often lack the capacity and the resources to establish and sustain centrally purified water free from
sewage.
Contamination of water during collection, transport, and storage at home
presents a serious risk to health for millions of households in developing
countries. Several studies have shown an increased risk of diarrhoea because of
inadequate water storage. Regardless of where or how the water is
collected, storage vessels with wide openings such as pots or buckets are easily
contaminated with faeces, through the introduction of cups, dippers, or hands.
Water might also be contaminated by flies, cockroaches, and rodents.
Several organisations have adopted a three pronged approach for treating
water at the point of use. This includes using simple household bleach (sodium
hypochlorite) to disinfect the water, using narrow mouthed storage vessels, and
working with communities to educate people about the causes and prevention of
diarrhoea. It has proved difficult to convince people to add bleach to drinking
water because it affects the taste. Moreover, bleach may not be effective in
water that is turbid or contains chlorine resistant organisms such as Cyclospora
cayetanensis or Cryptosporidium parvum. Until recently, interventions to improve
the safety of water and sanitation have focused on safe disposal of excreta and
proper use of water for personal hygiene rather than on paying attention to
water quality. The focus is now changing. A recent review by the World Health
Organization found that low cost simple and acceptable interventions in
households can improve the biological quality of water stored in the home and
hence reduce the risk of diarrhoea and death. Such interventions include
boiling, chlorination, and coagulation-flocculation. Unfortunately, boiling
consumes a lot of energy (it takes 1 kg of wood to boil 1 litre of water) and
the cost may be prohibitive, particularly in the developing countries where wood
and other biomass fuels are not always available. Moreover, burning wood can
lead to deforestation with serious environmental degradation.
Various interventions may remove particles and microbes from water. Although
cloth has been found to remove zooplankton and phytoplankton carrying Vibrio
cholerae and is used extensively for the eradication of guinea worm, cloth is
not recommended for routine treatment of water in the home because its pores are
too large to remove bacteria and viruses. Chemical precipitation (coagulation
and flocculation) removes particles and microbes. It can be used in households
to reduce transmission of diarrhoeal disease but its use in developing countries
has been limited by issues of safety, effectiveness, cost, and sustainability.
This is why the paper by Crump et al in this week's BMJ is an important
advance in treating water in households. In a randomised controlled trial, the
authors compared standard practice with flocculant-disinfectant treatment of
drinking water with sodium hypochlorite (bleach) in homes in a rural area of
western Kenya, where the water is highly turbid and contaminated with faecal
bacteria. The treatment lowered the turbidity of drinking water, improved the
acceptability of water treatment at home, and reduced the prevalence of
diarrhoea by 25% among participants.
The authors also report fewer deaths in the intervention group than in the
control group. It is not clear, however, whether the study had enough power to
detect a significant difference in mortality, and these results on mortality
reduction need to be confirmed in an appropriately powered, randomised
controlled trial. The authors claim that, if the flocculant-disinfectant
treatment were available in the marketplace, the visible effect on water
turbidity might lead families to treat water in their homes. Yet there is no
evidence to show that, in this community or indeed in other communities in the
region, people would be encouraged by such results to purchase.
This study is, nevertheless, an important addition to the list of randomised
controlled trials on the effect of flocculant-disinfectant on the quality and
acceptability of drinking water. The challenge now is to demonstrate
affordability, sustainability, and the feasibility of scaling up such
interventions to reach the millions of households in developing countries that
lack safe drinking water.
James K Tumwine, professor
Department of Paediatrics and Child Health, Makerere Medical School, PO Box
7072, Kampala, Uganda (jtumwine@imul.com)
(Source: BMJ 2005331:468-469 (3 September), doi:10.1136/bmj.331.7515.468)
For references see: http://bmj.bmjjournals.com/cgi/content/full/331/7515/468?etoc
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