Electrochemical oxidation with the aerobic pretreatment process for sulfate-rich tannery effluent

The anaerobic feed of tannery effluent was treated using a new invention of an integrated approach: electrochemical oxidation with aerobic pretreatment, which reduces the chemical oxygen demand (COD) and sulfur/sulfide gas formation. Bacterial consortium was used in the present study isolated from a common effluent treatment plant (CETP). Microbial community analysis of anaerobic feed of tannery effluent (AFTE) was done by next generation sequencing. Under aerobic treatment, 79% and 85% of COD reduction were achieved during 3rd and 5th days of the aerobic process. The electrochemical oxidation process was applied for 60 min to reduce the remaining COD using the current density of 20 mA/cm². Ti-TiO₂/IrO₂/RuO₂-coated mesh and titanium sheet were used as anode and cathode respectively in an electrochemical reactor. A separate electrooxidation experiment was also carried out with galvanostatic mode of constant current density (20 mA/cm²) which enhanced the duration of electrochemical oxidation up to 13 h for complete reduction of COD concentration. UV-Vis and NMR spectroscopy were used to confirm the degradation of organic matter in the tannery effluent during aerobic and electrooxidation processes, where aerobic bacterial degradation is significant. The presence of mixed salt chloride and sulfate was recovered and the elemental composition was confirmed by EDAX analysis.