AWWA JAW52065

The hybrid process resulting from adding powdered activated carbon (PAC) toultrafiltration (UF) reactors is being used to remove organic compounds infull-scale drinking water treatment plants. One way to increase the adsorptionefficiency of PAC is to add it to continuously stirred tank reactors (CSTRs) orto plug flow reactors installed upstream of the membranes. Additionally, the PACthat is recovered from the membrane backwash can be recycled to a floc blanketreactor (FBR) installed upstream of the PAC/CSTR-UF process. This study developedan adsorption model that predicts the removal of dissolved organic carbon (DOC)in the FBR-PAC/CSTR-UF system. The model was verified experimentally using twocommercially available PACs in a laboratory-scale pilot unit. Removal of DOC bycoagulation with aluminum salts and adsorption on the recycled PAC in the FBRsubstantially reduced carbon use. The model was used to assess the effect ofvarious operating parameters on DOC adsorption efficiency and to determineoptimal operating conditions. Includes 15 references, tables, figures.