AWWA WQTC57191

Ballasted sand flocculation (ACTIFLO) and dissolved air floatation (DAF) are two advanced pretreatment systems that were evaluated in this study against conventional pretreatment for the reduction of turbidity, total organic carbon (TOC) and disinfection byproduct formation potential. Based on tests, the optimal operating parameters for the DAF process are as follows: 15 mg/L coagulant dose, ambient pH, recycle rate of 10% and loading rate of 12.5 gpm/ft2. The optimal operating conditions for the ACTIFLO process are: 0.20 mg/L cationic LT22S polymer dose, 15 mg/L coagulant dose, ambient pH, and loading rate of 30 gpm/ft2. The ACTIFLO system was found to perform best in terms of turbidity, TOC, and disinfection byproducts formation potential reduction. Both the ACTIFLO and the DAF processes performed better than the conventional system. Filter backwash water was adequately treated by both the ACTIFLO and DAF systems. Residuals from the two processes were evaluated for treatment by gravity settling and dewatering. Residuals from the ACTIFLO process was difficult to treat and required additional treatment steps compared to the DAF system. Includes 2 references, tables, figures.