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SUMMARY: Idku lagoon is one of the northern delta lakes, connected with the Mediterranean Sea through Boughaz El Maadyah. It is subjected to industrial, domestic and agricultural pollution. Depending on collected data of water samples during one year of research, the lagoon was separated into different water masses by using the discriminant function analysis (DFA). Estimation of some biological (total and saprophytic bacteria, faecal bacteria and chlorophyll-a) and chemical variables (chlorosity, organic matter, dissolved oxygen and dissolved inorganic nutrients) lead to differentiate Idku lagoon waters into four sites: Drain (I), Lake Proper (II), Bay (III) and Boughaz (IV). The highly effective parameters for the predicted sites were chlorosity, organic matter and faecal bacteria (E. coli). Factor analysis was applied for each site to find out the correlating variables (biological and chemical) that seemed to control each independent site. At Drain site (I) pollution by agricultural sewage (through Idku Drain) supported bacterial as well as algal growth, while at Lake Proper site (II) bacteria seemed to obtain their nutrient supply from algal origin after their death and lysis. Site II was characterized by its absolute highest chlorophyll-a content. Factor models for sites II and III indicated a positive and mutual relationship between bacterial microbiota and chlorophyll-a. The strong correlation that appeared between all biota from factor model for site III, at the absolutely high chlorosity values (compared to the other sites), could be due to the development of salt tolerant strains and species. Factor model for site IV revealed a strong positive correlation between bacterial microbiota and nutrients (derived from industrial pollution at Boughaz El Maadyah), but negatively correlated to chlorophyll-a. Thus it seemed that bacteria obtained their nutrient supply mostly from sewage.

Azollafiliculoides is a free-floating water fern which fixes atmospheric nitrogen in association with the nitrogenfixing blue-green alga Anabaena azollae. It is used for nutrient-removal purposes because it can grow under a wide range of environmental conditions. This paper describes a series of experiments which was carried out in Alexandria, Egypt, to elucidate the performance of Azolla for the treatment of sewage and nutrient removal.

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