Pilot studies for the application of triple media filtration at Morton Jaffray Water Works, Harare, Zimbabwe

Abstract

Lake Chivero, Harare's main source of raw water for drinking water, is algae infested thus affecting water treatment processes at Morton Jaffray Water Treatment Works (MJWTW). Consequently, several challenges have been encountered including frequent filter backwashing, leading to a reduced plant output. In this study, the potential of substituting single-media filters (currently used at MJWTW) with triple-media filters was investigated. This was done using pilot filters of a single-media filter (SMF) and a triple-media filter (TMF) and piloted using clarified water from MJWTW. Electrical conductivity (EC), pH, total dissolved solids (TDS), turbidity, and temperature were the water quality parameters that were monitored. Headloss and flow rate were the filter operation parameters that were monitored. Both water quality and operational parameters were monitored at hourly intervals until one filter reached the maximum allowable headloss or turbidity limit. The variation in effluent turbidity, TDS, EC, and pH between the filters was insignificant. Nevertheless, the headloss development for the TMF was significantly slower than that of the SMF resulting in the SMF reaching the maximum headloss earlier. Therefore, the TMF performed better overall. Therefore, the adoption of TMF could result in a longer filter run and improve filtration and water production at MJWTW.