Removal of Biorefractory Compounds in Industrial Wastewater by Chemical and Electrochemical Pretreatments

The goal of this research was to investigate the effectiveness of chemical and electrochemical pretreatments in removing biorefractory compounds from a complex industrial wastewater. The presence of recalcitrant compounds in wastewater reduces the effectiveness of traditional biological treatments; in this case, the COD reduction was around 30%. Therefore, some pretreatments are required to eliminate the toxic substances and improve the biological efficiency. Chemical coagulation was evaluated using the standard jar testing technique with aluminum and iron sulfates and aluminum polyhydroxychloride (PAC). The best pollutant reduction was obtained when 4 mL dm(-3) of PAC was added to the industrial wastewater. At the same time, a batch aluminum electrochemical reactor was used, and better COD and color reductions were obtained as compared to those obtained with the chemical method. After being subjected to the pretreatment, the wastewater was introduced into a laboratory-scale biological reactor in which the COD reduction was monitored, and a global reduction of 68% was obtained using the electrochemical + biological method.