Using PAC–UF to treat a low‐quality surface water

Abstract

In a pilot study, a PAC‐UF process shows promise in treating a low‐quality source water without sacrificing either cost or operating efficiency.A water supply from a Midwestern agricultural watershed was treated using a hybrid powdered activated carbon‐ultrafiltration (PAC‐UF) pilot system. The pilot was operated remotely over a four‐month period using five combinations of target flux and backwashing frequency. Simple statistical techniques were used to analyze energy and cost efficiency for each combination. Energy use was minimized when target flux and the period between backwashes were minimized. Total cost was minimized when the target flux and period between backwashes were maximized. A degradation in water quality at the end of the pilot‐testing period presented a significant operational challenge that was overcome through the direct addition of 14 mg/L ferric chloride to the UF recirculation loop. The sudden degradation in water quality is testimony to the need for pilot tests designed to evaluate the effects of seasonal water quality variations.