Treatment of slaughterhouse wastewater with the electrochemical oxidation process: Role of operating parameters on treatment efficiency and energy consumption

Abstract

In this study, investigation of the applicability and efficiency of electrochemical oxidation (EO) processes for slaughterhouse wastewater was targeted by evaluating the treatment efficiency and energy consumption values together. The effect of operating parameters such as type of supporting electrolyte (SE) (Na2SO4, NaNO3 and NaCl), concentration of SE (0.01-0.1 M), initial wastewater pH (3–9), current density (CD) (4.73–14.20 mA/cm2) and dilution rate of wastewater (1/1-1/4) on removal of chemical oxygen demand (COD), total organic carbon (TOC), total nitrogen (TN), total suspended solids (TSS) and color were investigated. The most effective electrolyte type was observed as NaCl. With the use of 0.025 M NaCl and 25 °C reaction temperature, at fixed 4.73 mA/cm2 CD and pH of 7.03 for 4 h reaction time, the optimum conditions for both energy consumption and removal efficiency for treatment of SWW were obtained. At optimum conditions, TSS, TOC, COD, TN and color removal efficiencies were found as; 99.5%, 88.0%, 92.2%, 93.5% and 99.9%, respectively, and the energy consumption under these conditions were 153.57 kWh/m3 and 14.12 kWh/kg COD. The energy cost was calculated as 1.69 $/kg COD. Also, results distinctly show that almost full mineralization of organics is obtained after 4 h treatment. Unluckily, taking into account the large volumes of effluent produced per slaughtering cycle, the need for long treatment times is impractical, yet if the reactor is developed to include hydrodynamic conditions or combined with another treatment process which is shorter than the EO treatment time a novel setup may be possible.