Treatment of high turbidity water through plain and coagulated up-flow roughing filter

Abstract

AbstractKhokhar Zar Dam in Chakwal, Pakistan, serves as a main source of water supply to the area. This water is not only turbid but also biologically polluted. A hybrid slow sand filtration (SSF) plant, involving coagulation and sedimentation prior to SSF, is employed for the treatment. The treatment train is sensitive to wide variations in raw water turbidity and often results into short filter runs. Major objective of this research was to study the existing treatment process and conduct a pilot-scale investigation for the most appropriate treatment scheme, using an up-flow multistage roughing filter. A three-stage up-flow roughing filter (UFRF) was tested in plain and coagulated mode for a range of flow rates. Results showed that raw water turbidity reduced to 30 NTU in dry period and rose to over 2000 NTU after rainfall, whereas raw water pH and conductivity remained consistent. Jar tests showed that higher FeCl3 dose (65 mg/L) would be required when compared with alum (47 mg/L). Plain multistage UFRF...