Studies on the Evaluation of Biocenosis in Sewage Oxidation Ponds for Fish Culture

Abstract

Studies were conducted to assess the impact of Biocenosis on water quality parameters like temperature, pH, conductivity, total alkalinity, chloride, dissolved oxygen and carbon dioxide in the sewage oxidation ponds at Ambo University campus, Ethiopia. The phytoplankton of 10 genera belonging to Chlorophyceae, Bacillariophyceae, Euglenoideae and Cyanophyceae as well as z ooplankton such as rotifers, ostracods and copepods were observed. The major benthic fauna recorded were seven genera of insects and a single genus of oligochaete and nematode respectively. Three dominant bacterial genera namely Enterobacter sp, E-coli and Pseudomonas sp. were isolated from the water. In McConkey agar medium the mean density of the bacterial population was found to be 27 x10 3 , 29 x10 3 and 6 x10 3 in the three ponds respectively. Whereas, in the Pseudomonas agar they were found to be 79 x10 3 , 74x10 3 and 107x10 3 respectively in ponds 1, 2 and 3. However, in the nutrient agar, the bacterial colonies were moderate in numbers and the mean values were 22 x10 3 , 37 x10 3 and 17x10 3 in pond 1, 2 and 3 respectively. The results on the physico-chemical parameters indicated that the alkaline pHand high dissolved oxygen in the second and third oxidation ponds were within the permissible level for fish culture. Further, the results on the phytoplankton also revealed the high photosynthetic activity which enhances oxygen content and production of live food organisms.