Application of GAC adsorption in pulp and paper mill effluent treatment.

Abstract

Aerated stabilization basins (ASB) and activated sludge treatment (AST) are the most popular unit processes in the treatment of Pulp and paper mill effluents. However, these traditional biological processes can only provide partially satisfactory treatment because many components in pulp and paper mill wastes are persistent under the conditions of these processes. This study evaluated the application of granular activated carbon (GAC) adsorption using fixed-bed columns in the post-treatment of the whole-plant effluent of a Kraft and fine paper manufacturer. A mathematical model, the branched pore or dual rate model, was used to simulate the GAC column adsorption process. The computer program PRECOS was used to solve the model. The wastewater was first treated using a traditional AST system and then filtered and passed through a small-scale GAC column to obtain data for estimating mass transfer coefficients of the model. CalgonRTM F400 GAC was used. Isotherm studies were carried out for column influents to determine the adsorption capacity of the GAC. A simplified form of the dual rate model was used to predict the column performance in terms of treatment efficiency, consumption of carbon, and organic removal. The mass transfer coefficients of the model were determined based on microcolumn experimental data. The performance of AST system followed by GAC column adsorption process was compared to that of a PACT(TM) system in the treatment of a similar wastewater. It was found that for an overall COD removal of 80%, the carbon usage rate of the PACT(TM) system was 30% lower than that of the GAC column system. The lower performance of the GAC column system was attributed to a possible low efficiency in terms of carbon usage in the microcolumn experiment. A direct comparison between the two systems based on experiments is also needed.