Treatment of real dairy wastewater by electrolysis and photo-assisted electrolysis in presence of chlorides

Abstract

The efficiency of electrolysis (EC/Cl₂) and photo-assisted electrolysis (EC/UV/Cl₂) methods, in the presence of chloride, for the abatement of real dairy waste from a producer in the Triangulo Mineiro region of Brazil, was evaluated. A complete 2³ factorial design was performed for the variables time, pH and current. After determining the ideal pH, a Central Compound Design (CCD) was performed, where the applied current (533.42 mA) and treatment time (60.45 minutes) were maximized. The effluent was subsequently submitted to prolonged EC/Cl₂ and EC/UV/Cl₂ treatment in order to evaluate the behaviour of specific environmental parameters over time. The EC/UV/Cl₂ method was more efficient than simple EC/Cl₂ treatment. The EC/UV/Cl₂ method resulted in a reduction of all environmental parameters investigated to levels within legal standards for effluent discharge. A relatively low cost of treatment is obtained with Energy per Order (E_EO) values of 0.89 and 1.22 kWh m^-3 order^-1 for the EC/UV/Cl₂ and EC/Cl₂ treatments, respectively. The electrochemical production of free chlorine species followed by subsequent photolysis and production of radical species can convert a simple electrochemical process into an advanced oxidation process (AOP).