Efficiency of Pumice-Sand Granular Filter in Removing Effluent Wastes in Shirere Wastewater Treatment Plant in Kakamega County, Kenya

Abstract

Release of effluent directly from Aerobic maturation ponds into natural water bodies without more filtration has presented to be un optimal. Consequently, people down streams are exposed to greater risk of contracting waterborne diseases such as cholera, dysentery and typhoid. Skin problems, eye infections, and diarrhoea have all been linked to a lack of clean water and sanitation among community members. Introduction of filtering technologies such as sand, biochar, coconuts, pumice and crushed stone aggregates have been inadequate to treat the municipal waste water quality. 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 consequence, its waters have been shown to be increasingly getting covered by algae which indicate the presence of cyno-bacteria that is very toxic to human and animal health. Thus, the objective   of this study was to determine the efficiency of the pumice-sand granular filter in removing wastes in Shirere wastewater treatment plant in Kakamega. The wastes were Nitrates, Phosphates, BOD, COD and TSS. This objective was assessed under varying filter depths, effluent flow rate into the filter and seasons. Effluent, drinking water from protected springs along river Isiukhu, were collected using pre sterilized water sampling containers for microbial quality analysis at MMUST and KACWASCO laboratories. Sampling strategy was purposeful while sample size was 8 for water, 28 for waste water. Research design was experimental and data analysis used, regression and correlation methods. The average reduction of COD in the mid-season of June to August was 42.2 ±4.66%, being the highest. Concomitantly, BOD removal by the filter in the season of June to August was19.6±7% and 15.6 ±9.5% 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 18±7% of March to May. The average rate of Nitrate removal in June to August was 41.8±7.6% followed by 30±22% 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±6.7% followed by 20.6±4.8% for September to November and 20 ±10% for March to May. This shows a trend of high efficiency in dry season of June to august and march to May followed by September to November.  The use of composite filters in wastewater treatment reduced the organic matter intake, resulting in oxygen levels that were within natural values.  Findings of this study will influence waste water management policies and improve new technologies in waste water treatment for sustainable development. From the results, its therefore recommended that the composite filter technology should be applied to non-compliant sewerage treatment plants.