Electrocoagulation of yogurt industry wastewater and the production of ceramic pigments from the sludge

Abstract

In this study, the treatment of strained (condensed) yogurt wastewater using a uniquely designed iron reactor with electrocoagulation and the sludge produced during the electrocoagulation as a raw material in the production of ceramic pigment were investigated. A rectangular iron cathode compartment and parallel plate anodes were used, and various operating parameters, such as the current density, the electrolysis time, the supporting electrolyte concentration, the initial pH and the polyelectrolytes addition, were examined in order to determine the best conditions for intensifying the performance of the process. It was seen from the experiments that the COD removal efficiency was increased with the increasing current density from 20 to 30 mA/cm(2) and time while it was decreased with the increasing Na2SO4 concentration from 0.05 to 0.2 M. The best treatment efficiency was observed at the original pH of the wastewater (pH 4.53) and the cationic polyelectrolyte showed better performance than the anionic polyelectrolyte. The strained yogurt wastewater, with a COD concentration of 6500 mg/L, was treated with a removal efficiency of 84% after 90 min of electrocoagulation with the addition of 0.75 g/L cationic polyelectrolyte. The sludge produced during the electrocoagulation was characterised and used as an iron source to produce brown and black inorganic ceramic pigments because of their high iron oxide content. The results show that this specially designed electrochemical reactor is an effective alternative for the treatment of strained yogurt wastewater. It also shows that the sludge produced during electrocoagulation can be used as a raw material in the ceramic industry and that it can be converted from waste to a value-added product