Optimization of coagulation-flocculation process for medium density fiberboard (MDF) wastewater through response surface methodology

This paper compares performance of alum, polyaluminum chloride (PAC), and polelectrolyts (PE) as coagulants to remove suspended solids from wastewater of medium density fiberboard (MDF) manufacture. Response surface methodology was used to optimize coagulation-flocculation (CF) process of MDF wastewater. In the treatments with alum, results revealed that full quadratic model was more adequate for chemical oxygen demand removal and total suspended solids removal, whereas linear squares model was accurate for turbidity removal. In the treatments with PAC and PE, linear squares model had the highest accuracy for all the responses. The linear term of coagulant dosage (X-1) had the largest effect on the responses in the CF process of MDF wastewater with alum and PAC; whereas, the linear term of mixing time (X-3) had the largest effect on the responses in CF process of MDF wastewater with PE. Among the coagulants used in this study, it is concluded that PE was as the best coagulant for CF of MDF wastewater. The optimal conditions of the CF process using alum were 1,500mg/L dosage, pH 3, and 175s mixing time. The conditions of 1,500mg/L dosage, pH 7, and 137s mixing time were found as the optimum CF conditions of MDF using PAC. For PE coagulant, 20mg/L dosage, pH 8.8, and 135 s mixing time were found as the optimal conditions for the CF process of MDF with PE.