Electrochemical decolorization and biodegradation of tannery effluent for reduction of chemical oxygen demand and hexavalent chromium

Tannery effluent contains enormous quantities of toxic chemicals and high level of chemical oxygen demands, which gets directly discharged into natural aqueous system, thus contaminating the water quality. Hence, it is important to develop an eco-friendly and cost effective technology to treat the tannery effluent wastewater. Our present investigation on integrated approach of electrochemical oxidation (EO) of tannery effluent (TE) using RuO2-IrO2-TiO2 anode and titanium mesh electrode as cathode and followed by the biodegradation process (BP) of the treated EO effluent. Various parameters viz., sodium chloride concentration (NaCl) (1-5 g/L) and current density (10-30 mA/cm2) are optimized. The agro waste peanut hull (PH) and rice hull (RH) are utilized as carbon source for biodegradation of tannery effluent. A maximum of 87% decolorization is observed at 5 g/L of NaCl concentration and 30 mA/cm2 of current density after 135 min of EO treatment. The EO treated TE is further treated by BP with Pseudomonas stutzeri MN1, Acinetobacter baumannii MN3 and mixed consortia of MN1 and MN3. The 97% of chemical oxygen demand (COD) and 96% of Cr(VI) reduction was observed after 72 h of BP with mixed consortia and rice hull as carbon source. Thus, the integrated approach of EO with BP can be implied for complete a decolorization and degradation of tannery effluent.