A pilot-scale study of potable reuse impacts on surface water treatment

Interest is growing in direct potable reuse where advanced-treated water and raw water are blended and fed directly to a water treatment plant (WTP). However, the impacts of raw water augmentation on treatability at drinking water treatment plants have not been studied extensively. A pilot-scale treatment system, consisting of coagulation, flocculation, sedimentation, and filtration, was set up at a WTP to treat potential future blends of advanced-treated water and current raw water. The pilot plant was run with blends from 20% to 100% advanced-treated water at a range of filtration rates (2–9 gpm/sf) and coagulant doses. Under all conditions, filterable water was produced, achieving acceptable turbidity removal. Turbidity removal by sedimentation was variable (30%–90%). Filtration performance was more consistent, exceeding 90% turbidity reduction under all conditions and achieving lower headloss accumulation rates at higher advanced-treated water share. These results are optimistic for potable reuse schemes featuring raw water augmentation.