The sanitary condition of rural drinking water in a Nile Delta village II. Bacterial contamination of drinking water in a Nile Delta village

Whilst the major danger associated with drinking water is that it may be contaminated with sewage or human excreta, the danger of pollution from animals must not be overlooked. Outbreaks of infection from drinking water are frequently reported (Melnick & Gerba, 1979) and high prevalence rates of diarrhoeal diseases have been found in the Nile Delta (Sallam et al. unpublished data). The supply of potable water is a critically urgent national problem and is of especial importance to communities which must rely on poorly designed supply systems and which lack even the minimum quality control services. The bacteriological control of potable water depends on counting certain micro-organisms as indicators of faecal pollution. Although pathogenic coliforms other than Escherichia coli are found in faecal material, their low frequency makes it difficult to use them as indicators of pollution (Papavasilliou, 1958; Dufour, Strickland & Cabelli, 1975); however counts of E. coli may be relied upon as indicators of pollution (Hufham, 1974). A study of the ratio of E. coli to faecal streptococci provides an indication of the source of pollution, a ratio less than 0.7 indicates an animal source, whilst a ratio over 4 indicates a human source (Geldreich & Kenner, 1969). Although the village studied is supplied with municipal treated water, over 90 % of the villagers still use water after storage in a 'Zir' since this provides cooled water (El Shafhy, unpublished data). The zir is an earthenware, conical-bottomed vessel through which water seeps and evaporates, cooling the remainder. This paper reports a bacteriological study of tap water and zir water in one village.