The effects of intermittent supply and household storage in the quality of drinking water in Maputo / Förändringar i dricksvattenkvalitet i Maputo på grund av intermittent försörjning och tanklagring i hushållen
A serious problem arising from intermittent supplies is the associated high level of contamination and public health hazards resulting either from ingress of contaminated water or from prolonged storage. This paper discusses the overall condition of the drinking water quality of intermittent water supplies in Mozambique. The network of Maputo is used as an example. Records of water quality determinations from different locations in the network are used to assess the final quality of water at consumer’s taps. Chlorine residual levels measured in reservoirs and results of bulk chorine decay tests performed with samples of treated water are used to estimate chlorine decay constants (kb) at different locations of the network and to predict the influence of retention time in the final quality of water. Presence of bacteria, low disinfection capacity and long residence times in the network and reservoirs are the main factors affecting the final quality of distributed water. Post-contamination due to ingress of contaminated water and prolonged storage in reservoirs is high. The intermittent operation of the distribution network is therefore inadequate to guarantee safe drinking water.