Alternatives for Improving Biological Treatment Performance of a Pulp and Paper Wastewater

The treatment of wastewater generated at pulp and paper mills has mostly consisted of aerated stabilization basins (ASBs) and to a lesser extent activated sludge treatment (AST) systems. However, lower effluent limits for biochemical oxygen demand (BOD) as well as limits for nitrogen and phosphorus are generating renewed interest in other biological treatment technologies. An alternative biological treatment technology is the moving bed biological reactor (MBBR). In this project, the ASB and AST technologies were compared to pre-treatment by MBBR followed by the ASB process. The comparison was performed by conducting bench-scale treatability tests which enabled analyses of effluent quality and settling rates in a controlled environment. The comparison showed that the system using MBBR as pre-treatment yielded better settling biosolids than either the ASB or the AST systems alone. Additionally, the MBBR pre-treatment process enabled the downstream ASB process to achieve lower effluent chemical oxygen demand (COD), BOD, color and ammonia concentrations than either the ASB or the AST treatment technologies.