Abstract

In developing countries, urban surface waters are particularly affected by faecal pollution from domestic wastewaters due to the lack of sanitation and wastewater treatment plants. The presence of pathogenic microorganisms limits the uses of these waters for recreation and economic activities. In Ivory Coast, due to the important gap between water demand and water supply in urban areas, use of surface waters for the production of drinking waters becomes a serious alternative. Actually, there is no monitoring program to control pollution discharges into these surface waters. In this study, a monitoring study was planned from September 2015 to February 2017 in order to evaluate the level of faecal pollution of the Aghien lagoon, a potential drinking water supply located in Abidjan. Based on the enumeration of faecal indicator bacteria (Escherichia coli and Intestinal enterococci), microbiological water quality from Aghien Lagoon and its tributaries were evaluated. Abundance of faecal indicators ranged between 1.72 × 10¹ CFU.100 ml^-1 and 1.48 × 10² CFU.100 mL^-1 for E. coli and between 2.26 × 10³ CFU.100 mL^-1 and 7.72 × 10³ CFU.100 mL^-1 for IE in lagoon waters. The abundances of FIB observed in tributaries were higher than those observed in lagoon water. The tributaries comparison indicates that, the Djibi River is the most contaminated with an average value of 1.73 × 10⁶ CFU.100 mL^-1 for IE and 6.92 × 10⁵ CFU.100 mL^-1 E. coli mL. The contributions of tributaries in terms of faecal bacteria discharged into the Aghien lagoon are not negligible and these contributions are significantly different between the dry and rainy season. Therefore, lagoon water may be a potential drinking water supply if wastewater treatment plants are implemented in the Djibi and Bété basins.

Key words: Water quality, faecal bacteria, drinking water supply, tropical lagoon.