Microbial removal efficiency of a natural wastewater treatment system and the impact of its effluent on receiving waters

Abstract

The discharge of untreated or partially treated wastewater into streams is a huge problem in developing countries in that it leads to severe environmental degradation, and, also, poses serious public health challenges to communities which live downstream. The study investigated the microbial removal efficiency of individual ponds of a waste stabilization pond system and the overall performance of the treatment systems in the removal of indicator bacteria and organic matter. The impact of the discharged effluent on the receiving waters was evaluated. The final effluent concentration of BOD and TSS were 1.7±1.2 and 10.1±4.3 mg/l, representing overall removal efficiencies of 98.7 and 98.6 percent, respectively. Overall log removal of faecal coliform (FC) and E. coli were 3.8, and 4.7 log units, representing a percentage removal of 98.4 and 99.8 percent, respectively. The mean diversity upstream was 0.11±0.09 while the downstream was 0.14±0.05, and this was not statistically different. The presence of macro-invertebrate families of Elmidae and Libellulidae downstream the point of discharge is an indication of good water quality