Electrochemical removal of organics and oil from sawmill and ship effluents

The present study investigates the electrocoagulation treatment of two different wastewaters, namely sawmill wastewater and ship waste effluent, charged with organic matter. Monopolar electrode configuration was studied for both types of effluents at current intensity of 2.0 A for a total treatment time of 90 min. Soluble chemical oxygen demand (CODs) removal was very low (12.5% to 13.6%) for sawmill effluent in comparison to 74.7% to 75.4% obtained for ship effluents. Thus, ship effluent was further examined in details for its treatment efficacy in terms of electrode configuration and type, current intensity, treatment time, and pH. It was observed that bipolar electrode configuration using the Al electrode at 0.3 A gave the highest CODs removal of 77%. Effluent pH increased rapidly in the initial 20 min with a concomitant decrease in CODs concentration. Electrocoagulated-flocculated ship effluent improved performance relative to simple flocculation with respective removals of 86% of turbidity, 56% of CODs; 69% of total COD (CODt), 90% of oil and grease, 94% of C-10-C-50 hydrocarbons and 89% of biochemical oxygen demand (BOD5). Residual Al3+ concentration in the solution followed a linear trend with treatment time. Meanwhile, the sludge production increased progressively during 60 min of treatment time. Total cost for treatment of ship effluent, including energy, electrodes, and sludge disposal fee is estimated between CAN$1.34 and CAN$2.40m(-3).