Household disinfection of drinking water

The lack of safe drinking water is one of the major causes of diarrhoea epidemics. This problem becomes acute after disasters when existing systems further deteriorate. Disasters, including floods, cyclones and tornadoes, are almost annual events in Bangladesh. This paper presents data collected following the cyclone of 1991. After the cyclone, people were supplied with water purifying tablets (WPTs). We collected WPTs from 16 different agencies who were involved in relief activities. The majority of the tablets (63%) were found to have lost potency. We strongly feel that there was a need for promoting other feasible options for household disinfection of water. We attempted to disinfect surface water supplies using bleaching powder and alum at different concentrations. Bleaching powder was found to disinfect water samples better than alum. To determine whether treated water was palatable, we prepared duplicate sets of 8 tube well samples containing either (a) 24 mg l^-1 bleaching powder, (b) 600 mg l^-1 alum, (c) active WPTs, or (d) no additives. The samples were tested by volunteers. All samples were considered palatable except for that treated with 600 mg l^-1 alum. The study results indicate that the effectiveness of water treatment methods should be tested under normal and disaster conditions and that educational efforts are essential.