Evaluation of a neglected waste stabilization pond

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A functional pond, among a series of three neglected ones was evaluated during a two month period for its operational efficiency by measuring the flow rates, Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Total Solids, Bacteria and Coliform counts, Nitrat.es and Phosphorus levels of both the influent and effluent. The influent flow rates of 290 metre cube per day were higher than the design value of 270 metre cube per day. The effluent flow rate was 230 metre cube per day. The ponds detention period of 7.6 days was markedly different from the design value of 53.6 days. The influent and effluent BOD were 210 and 21.5 mg/l respectively indicating 90% efficiency with respect to BOD reduction. The calculated surface loading BOD of the pond was 256 kg/ha/d which was less than the maximum of 751 kg/ha/d obtained with the fomular of McGarry and Pescod) that the pond can handle without failing. Levels of nitrate, phosphorous, and total solids in the influent and effluent indicated a higher efficiency of their removal in the effluent. The MPN and the Ammonia Nitrogen showed a very low performance. This shows that there is the need to further treat the effluent before discharging into a nearby river or better still to increase the detention period by increasing the volume of the pond. The condition of other ponds in the country is also included.
A thesis submitted to the Board of Postgraduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirements for the award of the Degree of Master of Science in Sanitary Engineering, 1988