Assessing the Efficiency of the KNUST Sewage Treatment Plant
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Date
JUNE 2009
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Abstract
It is well known that successive stages of treatment at a sewage plant reduce the
quantity of suspended solids, the organic matter content, the nutrient constituent, the
microbial load and the bio- chemical oxygen demand of sewage, so that the polluting
strength of the final effluent becomes a small fraction of that of the sewage received at
the plant. A performance efficiency investigation was therefore conducted on the
KNUST sewage treatment plant which treats sewage via percolating filters and humus
tanks. Samples taken at various stages of treatment over a period of four months were
subjected to microbiological and physico chemical examination to find the reductions in
levels of pollutants as the sewage goes through the treatment system. The studied
parameters included Temperature, Hydrogen ion concentration, Turbidity, Nitrate,
Phosphate, Biochemical oxygen demand, Total suspended solids, Escherichia coli,
Salmonella and Total coliform to assess the performance efficiency of the plant in
reducing their polluting strength. Plate count on nutrient agar of E. coli, Salmonella and
Coliforms were performed. Laboratory Chemical analyses were done for the physic-
chemical parameters including temperature, pH, Turbidity, TSS and BOD5, Nitrate and
Phosphate. The data as a whole gave a general picture of the extent to which treatment
at the works reduced the parameters at the various treatment units of the plant. The data
were analyzed using Microsoft excel and Statistical Package for Social Scientist (SPSS)
software packages. One way analysis of variance (ANOVA) was ran to determine
significant differences of the parameters per treatment unit of the plant.
After analyzing the data, it was evident that plant’s performance efficiency is below the
EPA Ghana standard as most of the parameters were not treated to meet standard for
discharge. The effluent discharged into the Wiwi River has pollutant levels of TSS,
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BOD5, Total Coliform, E. coli Phosphate and Nitrate being higher than the EPA
permissible levels for discharge. Turbidity was reduced by 82%, TSS by 86%, BOD5 by
68.9%, Phosphate by 72.8%, Nitrate by 70.5% E. coli by 91%, Salmonella by 77% and Total coliform by 91.1%.
Upon critical assessment of the performance of the KNUST Sewage Treatment Plant, it was found that operational design and administrative factors combined to cause the poor performance of the plant.
The plant lacked process monitoring and testing on which to base control decisions.
Excessive hydraulic loading (too much wastewater for the capacity of the STP)
impaired the performance of the plant. It is highly recommended that regular maintenance of the plant should be ensured and also competent and well resourced crew should be recruited to manage the plant.
Description
A Thesis submitted to the Department of Theoretical and Applied
Biology, Kwame Nkrumah University of Science And Technology In partial fulfillment of the requirements for the degree of MSc Environmental Science