ASSESSMENT OF COMPOSITE FILTER PERFORMANCE AND COMMUNITY KNOWLEDGE ON QUALITY OF EFFLUENT AT SHIRERE WASTEWATER TREATMENT PLANT IN KAKAMEGA MUNICIPALITY, KENYA

Abstract

Release of effluent directly from aerobic maturation ponds into natural water bodies has presented not to be very efficient. Consequently, people downstream are exposed to greater risk of contracting waterborne diseases such as cholera, dysentery and typhoid. Skin problems, eye infections, and diarrhea have all been linked to lack of clean water and inadequate sanitation among community members. Introduction of filtering technologies such as sand, biochar, coconuts shells, pumice and crushed stone aggregates have been used to treat the municipal wastewater. However, these have proved to be inadequate. Even then no effort has been made to apply such technologies in the removal of wastes discharged into River Isiukhu from Shirere waste water oxidation ponds. As a consequence, its waters have been shown to be increasingly getting covered by algae which indicate the presence of cyno-bacteria and other compounds toxic to human and animal health. The overall objective of the study was to assess composite filter performance and community knowledge on quality of effluent at Shirere wastewater treatment plant in Kakamega municipality. Specific objectives included; to determine the silica pumice composite filter performance efficiency at its optimal conditions; To develop a mathematical model for the removal of waste from effluent by composite granular filter at Shirere wastewater treatment plant; to evaluate the trend of effluent quality before and after installation of composite granular filter from Shirere wastewater treatment plant upto river Isukhu; to asses community knowledge, attitude and perception towards effluent quality discharged from Shirere wastewater treatment plant upto river Isukhu. Effluents, drinking water from Shirere WWTP, Shikoye stream, River Isiukhu and protected spring along Shikoye stream, were collected using pre sterilized water sampling containers for microbial quality analysis at MMUST and KACWASCO laboratories. The measurements were carried out using UV-VIS spectrophotometer at 752 nanometer wavelengths. Sampling strategies were purposeful and random. Sample size was 8 for water, 28 for wastewater. Research design was experimental. Data analysis used, regression and correlation methods. The average reduction of COD in the mid-season of June to August was 42.2 ±4.6%, being the highest. Concomitantly, the BOD removal by the filter in the season of June to August was19.6±7% and 15.6 ±3.5% for September to November. The average rate of TSS removal in June to August was 19.3±4.5% followed by 16.6±3.8% of September to November and 11.6±7% of March to May. The average rate of Nitrate removal in June to August was 41.8±7.6% followed by 30.0±2.2% for March to May and 25±8.6% for September to November. Phosphates had an average rate of removal in June to August as 31.9±2.7% followed by 20.6±4.8% for September to November and 20.0 ±4.3% for March to May. The use of filters in wastewater treatment reduced the organic matter intake, resulting in oxygen levels that were within natural values. Specifically, for the first season of March – May 2021 at 200mm filtration depth were carried out at effluent flow rate of 0.0032 and volume, 0.234 the model arrived at was .The model results showed minimal variation from the measured values. The first season measured COD as 0.236kg/m and model gave 0.2174kg/m. The model will be used in prediction of parameter concentrations at any given time. Concentrations of most parameters were above NEMA standards, like COD was322mg/l yet maximum should be 100mg/l. Community members need more sensitization on matters pollution as revealed by this study. Therefore, it was concluded that silica pumice composite filter performance is evidenced by big variations in the concentrations of COD, BOD, TSS, Phosphates and Nitrates at Shirere WWTP after filtrations which was attributed to effective filtering capacity. Similarly, the developed model, C=C_in (1-e^(-t(Q⁄V))) was found to be reliable in depiction of pollutant concentration by substituting time. The effluent concentrations from sampling sites S1-S3 and S5-S7 were found to above the NEEMA standards implying the high risk of Isukhu water and catchment area. It was also concluded that the level of knowledge of the community around Shirere Waste Water Treatment Plant had a negative attitude and no bearing on the effluent pollution into River Isiukhu. The study recommends that the composite filter should be applied in non-compliant WWTPs and the developed mathematical should be adopted for prediction of waste removal by substituting the values for time.