The role of wetlands in the treatment of raw sewage: a case study on a Kwame Nkrumah University of Science and Technology Wetland

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The study deals with the efficiency of a Kwame Nkrumah University of Science and Technology wetland in the treatment of sewage. It involved the identification of plants for future characterization of the wetland and for further development of the wetland into one that can reduce the level of sewage pollution to an appreciable extent. The study was carried out from May to November 1999. Parameters studied included temperature, pH, suspended solids, dissolved oxygen, biochemical oxygen demand, nitrates, phosphates, ammonia nitrogen, faecal coliforms, flow rate and minimum-residence-time. Statistical analysis revealed that with the exception of dissolved oxygen there were significant differences between influent and effluent sewage with respect to all the parameters considered. The characteristic average value of effluent parameters were as follows: temperature 27.7°C, pH 7.2, suspended solids 105.2 mg/L, dissolved oxygen 1.7 mg/L, biochemical oxygen demand 139.3 mg/L, nitrates 2.28 mg/L, phosphates 2.97 mg/L, ammonia nitrogen 7.08 mg/L, faecal coliform 1.85E+14 FC/l00ml and a minimum-residence-time of 22.0 minutes. The variation in student population on campus coupled with the dilution effect of rainfall and varying biochemical reactions influenced the results obtained. Comparison of results obtained with Ghana EPA standards showed that the performance of the wetland as a treatment process unit currently is far below standard requirement. This can be improved if organized engineering measures are put in place to allow the sewage to be contained in the wetland longer enough for appreciable changes in quality to occur.
A thesis submitted to the Department of Biological Sciences, Kwame Nkrumah University of Science and Technology in partial fulfilment of the requirements for the award of Master of Science degree in Environmental Science, 2002