| Abstract: | Observations were made over a period of one year on the performance of multi stage stabilization ponds treating domestic waste waters. The unit is composed of Primary anaerobic (P1) and two consecutive Secondary (P2) and Tertiary (P3) facultative ponds. The overall reduction in BOD, bacteria, PO4, SO4, NH3N, Cl− and total solids were 89.4, 99.8, 76.2, 47.7, 79.7, 18.6 and 74.0 percent, respectively. Elimination of H2S was 84.8% in the final effluents. Chlorella vulgaris was found to be the dominant alga followed by Euglena, Ankistrodesmus, Phacus and Synedra as subdominant forms. 9 species of protozoa have been recorded in the first pond and their number declined in the successive ponds. |
