Evaluation of Activated Carbon Adsorption for Removal of SOCs From Natural Water

Abstract

Two mathematic models, the modified equilibrium column model (MECM) and the pseudo single solute homogeneous surface diffusion model (HSDM), were developed in this study to predict the performance of powdered activated carbon (PAC) and granular activated carbon (GAC) adsorption systems for removal of low-level synthetic organic compounds (SOCs) from natural water.

The MECM assumes the GAC column adsorber as a plug-flow reactor for adsorption of a SOC and as a completely stirred tank reactor without GAC wasting for adsorption of background organic matter in natural water. The adsorption competition between the SOC and the background organic matter in the column is quantified using the equivalent background compound (EBC) method (Najm et al., 1991) coupled with the ideal adsorbed solution theory (IAST) (Radke and Prausnitz, 1972). The model predictions were verified by a pilot plant study conducted at Jefferson Parish, LA, for removal of dichloroethane (DCEA), trichloroethene (TCE), and tetrachloroethene (PCE) from clarified Mississippi River water.

The HSDM assumes the PAC adsorption systems as complete stirred tank reactors (CSTRs). The adsorption competition between the SOC and the background organic matter is quantified by the EBC method coupled with the IAST, and the adsorption kinetics of the SOC under the influence of the background organic matter is described by the pseudo single solute HSDM. The model was applied and verified for the adsorption of atrazine from Central Illinois groundwater using a bench scale CSTR and a PAC/Ultrafiltration (PAC/UF) pilot unit.