Tannery effluent treatment and its environmental impact: a review of current practices and emerging technologies

The tannery industry plays a significant role in the economy but poses a severe environmental threat due to its high water and chemical usage, leading to wastewater generation with a high concentration of pollutants. This wastewater contains a range of contaminants created throughout the leather manufacturing process, making effluent disposal a significant challenge for the industry. The tanning process also contributes significantly to the pH, biological oxygen demand (BOD), total suspended solids (TSS), chemical oxygen demand (COD), total dissolved solids (TDS), and concentrations of T Cr, Cr(III), Cr(VI), Cl-, sulfate, sulfide, and inorganic constituents in the wastewater. This review paper provides a concise overview of the origins and characteristics of post-tanning effluent, different treatment techniques, and applications of treated wastewater. Comparing the prominent tannery effluent technologies, adsorption and advanced oxidation processes (AOPs) effectively improved wastewater biodegradability before biological treatment. AOPs, enzymatic, adsorption, and coagulation treatment effectively upgraded the effluent to desired levels for disposal. Additionally, membrane separation processes have shown high pertinency in cases where the treated effluent is intended for reuse, whereas hybrid technologies can be the answer for better and cost-effective results.