Application of a Pilot-Scale Pulsed Electrocoagulation System to OCC-Based Paper Mill Effluent

There are increasing trends toward closure of white water recirculation loops in papermaking often leading to needs for system modifications. A pilot-scale study was conducted using pulsed electrocoagulation technology to treat the effluent of an old corrugated containerboard (OCC)-based paper mill, with the purpose of evaluating its treatment performance. The operating variables were a current density of 0~240 A/m2, a hydraulic retention time (HRT) of 8~16 min, and a coagulant (anionic polyacrylamide) dosage of 0~22 mg/L. Water quality indicators investigated were electrical conductivity, suspended solids (SS), chemical oxygen demand (COD), and true color. The results obtained during pilot-scale studies were encouraging. Under the operating conditions without coagulant addition, the highest removals for conductivity, SS, COD, and true color were 39.8%, 85.7%, 70.5%, and 97.1%, respectively (with an HRT of 16 min). The use of a coagulant enhanced the removal of both conductivity and COD. With an optimal dosage of 20 mg/L and a shortened HRT of 10 min, the highest removals achieved for the four water quality indicators were 37.7%, 88.7%, 74.2%, and 91.7%, respectively. The water qualities thus attained should be adequate to allow reuse of at least substantial portion of the treated effluent as process water makeup in papermaking.