[Prevention of cholera transmission: rapid evaluation of the quality of municipal water in Trujillo, Peru].

Unboiled, unchlorinated drinking water is known to have been associated with epidemic transmission of cholera in Trujillo, Peru, in February 1991. In September of that same year, chlorination of the main water supply system was begun. Water quality in Trujillo at the central level is monitored at dams and principal distribution points, but the effects of this surveillance on the quality of the water distributed are not known. In order to evaluate water quality in the residential areas of Trujillo, water samples were collected in February 1993 from 30 systematically selected houses. The chlorine levels in the samples were measured, and cultures for coliform bacteria were done. The free chlorine concentration varied from 0 to 1.5 mg/L (median = 0.4 mg/L). No free chlorine was detected in 5 samples (17%), and in 14 (47%) the concentrations were less than 0.4 mg/L. Coliforms were found in 16 samples (53%), but none were fecal coliforms. These results demonstrate the wide variability in chlorine concentrations in the municipal water that is distributed to dwellings. This variability, together with the need to store drinking water in the house because of shortages, supports the recommendation of the Ministry of Health that residents should treat drinking water in their homes. The simple sampling framework employed in this study provided a rapid evaluation of the quality of municipal water supplied to consumers. Similar studies could be carried out easily in other metropolitan areas where water quality is suspect, in order to rapidly obtain essential information on water quality at the level of the consumer.