Treatment of wastewaters of paper industry by coagulation–electroflotation

Treatment of paper effluent samples by coagulation–electroflotation was studied. The study aims to determine the best conditions of treatment which maximize the purification efficiency. For that, the methodology of experimental research with an orthogonal central composite design was adopted. Batch and continuous modes of treatment were studied. The batch mode aims to optimize coagulant concentration, pH and current density at fixed treatment duration. The current density is the most significant factor in the suspended solids elimination followed in decreasing order of importance by coagulant concentration and pH. Good agreement between theoretical analysis and experimental results was obtained. Continuous mode aims to optimize the residence time. Purification efficiency consisting in the elimination of suspended solids exceeded 95%. Physicochemical characterization of the effluent was done before and after the treatment in batch and continuous mode to improve the efficiency of this process. This characterization included pH, conductivity, salinity, BOD5, COD, suspended solids and chlorides.