AWWA MTC61169

Treating highly turbid waters with minimal pretreatment and the effect of polymer use on the membrane performance was investigated for this study. Typically, use of polymer upstream of membranes is not practiced since it may irreversibly foul the membrane; however, use of polymer could improve the performance of pretreatment processes, thereby improving the efficiency of the membranes. This paper discusses the effect of a cationic polymer up to doses of 150 mg/L and turbidity in excess of 100 NTU on a membrane system. WaterOne of Johnson County, Kansas, treats Missouri River water at a remote facility before it receives further treatment at the Hansen WTP. Treatment at the Missouri River facilities includes sedimentation with aluminum sulfate and a cationic polymer to reduce the turbidity of the raw water from as high as several thousand NTU to between 10 and 20 NTU. A pilot study was conducted to evaluate the performance of submerged ultrafiltration (UF) membranes on the settled Missouri River water. The treatment unit was set at a flux of 28 gfd and a recovery of 92 percent. During part of the study period, the recovery was increased to 96 percent in an attempt to quantify the effect of increased solids concentration on membrane permeability. The raw water turbidity was as high as 4,000 NTU during two separate occasions and the settled water turbidity exceeded 100 NTU. Polymer dosages as high as 10 mg/L applied at the pretreatment facility did not appear to adversely affect the membrane performance. Two additional polymer tests were conducted using incremental polymer doses up to 150 mg/L immediately upstream from the treatment unit. Following the polymer tests, the membranes were cleaned by CIP procedures to evaluate their recovery capability. Includes tables, figures.