Paper and board mill effluent treatment with the combined biological–coagulation–filtration pilot scale reactor

Pilot scale reactor based on combined biological–coagulation–filtration treatments was designed and evaluated for the treatment of effluent from a paper and board mill. Biological treatment by fed batch reactor (FBR) followed by coagulation and sand filtration (SF) resulted in a total COD and BOD reduction of 93% and 96.5%, respectively. A significant reduction in both COD (90%) and BOD (92%) was also observed by sequencing batch reactor (SBR) process followed by coagulation and filtration. Untreated effluent was found to be toxic, whereas the treated effluents by either of the above two processes were found to be non-toxic when exposed to the fish for 72 h. The resultant effluent from FBR-coagulation–sand filtration system meets National Environmental Quality Standards (NEQS) of Pakistan and can be discharged into the environment without any risks.