Steps for rehabilitation of a Lake suffering from intensive pollution; Lake Mariut as a case study

Abstract

Due to the acute water scarcity facing many urban areas, the water resource management, and lake rehabilitation become a global interest. Before applying the appropriate approach in the rehabilitation (restoration) of a hypereutrophic lake, the assessing of the point sources of pollution and their effects are A MUST. Lake Mariut is an example of lentic polymictic closed coastal Egyptian lake. The economic and recreational values of Lake Mariut were deteriorated since 1960s, as a result of using its Main Basin as a sink of wastewaters discharged from the agricultural Umum Drain and the heavily polluted Qalaa Drain mixed with primary treated sewage waters from Alexandria East Wastewater Treatment Plant. The aim of the current study is to find the suitable solution/s for the Lake Mariut Main Basin restoration, by (1) studying the general characteristics of its drainage water system (Umum and Qalaa Drains) at their downstream parts before reaching the lake at its southern side as well as the adjacent non-polluted Lake Mariut Fishery Basin. (2) Discussing (by calculation) the applicability of two proposed improvement solutions. The results reveal that, in the first the water quality of the anoxic Qalaa Drain must be improved by diluting its waters with oxic Umum Drain waters via Lake Mariut Fishery Basin prior discharging. This solution is found not sounding as it difficult to attain from practical point of view. The other alternative is by diverting the polluted Qalaa Drain point source itself away from Lake Mariut Main Basin water body which is sounding and highly recommended.