AWWA ACE63180

This slide presentation outlines a membrane retrofit project for an expanding small water system conventional treatment plant. The presentation outline includes: need for water plant upgrade and expansion; water source and treatment challenges; treatment alternatives analysis; description of selected membrane system design; and, project status. The water source and treatment challenges include: water source is Cosumnes River, withdrawal allowed only in winter; raw water storage in 3 small lakes that support numerous aquatic plants; lake source is low in turbidity but has elevated total organic carbon (TOC); and, average alkalinity is < 60 mg/L. Treatment challenges include: water source is low in total dissolved solids (TDS) and turbidity; aquatic plants in lakes add TOC; manganese can be present in lakes; and, enhanced coagulation with ferric chloride achieves 35% TOC removal. Treatment alternatives analysis: ruled out expansion using traveling bridge filters; alternative 1 - conventional flocculation/sedimentation dual media filters; and, alternative 2 - retrofit 1970s plant with submerged membranes. Description of selected membrane system design: membrane system capacity = 5 mgd (firm), 7.5 mgd total, process train includes automatic self-backwashing screens, five minutes contact time in floc basins, submerged membranes, and chlorine contact basin.