Investigating the quality of stored drinking water from the harare water distribution system, Zimbabwe

Abstract

This study investigated the effects of different storage conditions (refrigerator, cupboard and sunlight) on the quality of drinking water collected from the distribution system. The study was carried out in the period June–July 2017 and focussed on selected suburbs of Harare. Sampling sites on the distribution system were grouped into three zones (1, 2 and 3) depending on the proximity to the treatment plant, whether there was further chlorination or not and the water flow path. Three water samples were collected in opaque 5 L containers from one site (tap) in each zone and stored under the three storage conditions and periodically analysed for pH, free residual chlorine, temperature and chlorophyll-a. The pH of stored water increased with storage time for all storage conditions and in all zones. The residual chlorine decreased with time in all zones and under all storage conditions. The chlorophyll-a levels also decreased with time under all storage conditions. Refrigerator samples showed the slowest deterioration of water quality and sunlight the highest. Although the pH of stored water increased with time, it remained within both SAZ and WHO guideline values. Household disinfection of stored water is recommended generally after 1 week of storage.