Exploring the feasibility of dual media filtration at Morton Jaffray Water Works (Harare, Zimbabwe)

Lake Chivero, Harare's main potable raw water source, is eutrophic. This has complicated water treatment at Morton Jaffray Water Treatment Works (MJWTW) leading to frequent filter backwashing and reduced plant output. This study investigated the use of dual media filters (DMF) as an alternative to single media filters (SMF) currently employed using pilot filters. Key operational parameters (headloss and flow rate) and water quality parameters [electrical conductivity (EC), pH, total dissolved solids (TDS), turbidity and temperature] were monitored hourly. The change in EC, pH, TDS, and turbidity across the SMF and DMF was 6.3% and 6.3%; 0.5%. and 0.2%; 5.5% and 4.5%; 68% and 69%, respectively thus showing no significant difference. However, headloss development for the SMF was significantly higher reaching 247.3 m compared to 134.6 m for the DMF. Use of DMF could increase the filter run and production at MJWTW.