Household water treatment and safe storage

2005 International Symposium on Household Water Management

The 1-2 June 2005 symposium aimed to share the latest available information on household water treatment and safe storage, focusing on two key areas:

  • field and laboratory studies, to gain a better understanding of candidate technologies; and
  • different educational and motivational approaches, to improve practices introducing HWTS to households and promoting HWTS within households.

The 35 oral presentations, and 12 poster presentations also addressed a number of thematic areas including HWTS and emergencies, consumer perceptions and preferences, including willingness-to-pay, and household chemical removal systems. Technology demonstrations enabled participants to see water treatment devices working first-hand.

Thomas Clasen’s keynote presentation, “Interventions to improve water quality for the prevention of diarrhoeal disease: a systematic review,” summarized the results of his Cochrane review of household water treatment interventions. The data suggests that interventions at the household level are about twice as effective as those at the source, in some cases reducing diarrhoeal rates by 50% or more. However, much variation has been observed in diarrhoeal reduction rates, possibly related to user compliance. He pointed out the particular need for longer-term studies, blinded trials, and studies of immuno-compromised populations.

Following this, a number of lab and field studies examined the performance, health impacts, and user perceptions associated with a range of filtration approaches. The focus was on different forms of ceramic filters, usually coated with colloidal silver (a bacteriostatic), and the biosand filter. Intervention experiences suggest that there is a high degree of user satisfaction associated with filters as they are frequently straightforward to operate, improve the aesthetics of “dirty” water, and introduce no chemicals that can affect taste. A recent study suggests that addition of an iron oxide to ceramic filters can significantly improve their performance in trapping viruses. An on-going study of the biosand filter indicated that the time required to ripen the key biological slime layer can be significant (i.e. up to 30-40 days), and may vary considerably.

Various solar and chemical disinfection approaches were discussed, including SODIS, liquid dilute sodium hypochlorite (e.g. as used in the CDC Safe Water System), sodium dichloroisocyanurate tablets (e.g. as used in the product Aquatabs), solid calcium hypochlorite, and combined flocculant and disinfectants (e.g. as in the product PUR). It was noted that chlorine-based approaches leave a chemical residual to prevent recontamination of stored water, but like most HWTS systems, require accompanying behavioural change programs. Many of these technologies have been introduced over the last years in efforts to scale-up HWTS (e.g. in 21 countries for the Safe Water System). During the thematic session on emergencies, presenters highlighted the unprecedented product deployment in response to the Indian Ocean tsunami.

Several new technologies were presented, ranging from mature consumer-ready products (like the multi-barrier Pureit filter being marketed in India) to innovative new methods in the testing phase (use of a silane-coated surfaces to deactivate pathogens).

While it was agreed that technology development was important, it was noted that perhaps the greatest challenges related to the “software” side, for example, identifying successful approaches to motivate use of HWTS. Thus, research examining household perceptions, preferences, and practices was seen as a priority area for research. In this regard, field studies show that important considerations in home treatment are taste and other aesthetic properties of the water, convenience of use, willingness to pay, and cultural attitudes.

Presentations on this theme suggested that “positive” attitudes and ideas were better predictors of whether people were likely to consistently treat water than were negative attitudes. For example, educational and promotional messages should target positive ideas, such as clarity, taste, good health, affordability, and ease of use. Evidence also suggest that many householders would be willing to pay for home treatment at an acceptable price (e.g. less than US$ 10 for water filters in Southern Africa). Payment by installments may be one method of enabling the poor to deal with the relatively high up-front costs of certain technologies.

Participants noted that there was relatively little reported on interventions to improve water storage in the home, and recommended that this given a greater prominence in future symposiums.