Electrochemical removal and recovery of humic-like substances from wastewater

The secondary effluent from paper and food industry wastewater still contains a high chemical oxygen demand and color intensity caused by the presence of difficult degradable organic compounds. These compounds are mostly humic-like substances. This study focused on two promising electrochemical methods for removal and recovery of humic like substances from industrial secondary effluent: membrane electrolysis and electro-coagulation. Membrane electrolysis removed 70% of the color at energy consumption 3 kWh/m3. The chemical oxygen demand reduction in the electrolysis process was less efficient. Organic compounds were partly removed at the cathode by precipitation and partly transported to the anode side, which was dependent on the membrane material. The electro-coagulation treatment process efficiently removes chemical oxygen demand and color. The method has a lower operational cost compared to the membrane electrolyses and would be the best option for high polluted wastewater. These results show that the electrochemical methods are an interesting option for humic like substances removal/recovery and could compete with conventional oxidation and coagulation methods.

► We examine two promising electrochemical methods for removal of humic substances.
► In the membrane electrolysis experiment color was removed efficiently.
► Electro-coagulation efficiently removes chemical oxygen demand and color.
► Electro-coagulation has lower operational cost compared to membrane electrolysis.
► We found the electrochemical methods are interesting for humic substances removal.