Bioremediation for Tanning Industry: A Future Perspective for Zero Emission

Bioremediation is one of the recent technological advancements for treating heavy metals containing industrial wastes. Leather industry utilizes almost 90% of chromium-based tanning agent for converting raw skins/hides into leather. Apart from chromium, metals such as aluminum, titanium, iron, and zirconium are widely used for various end applications. Hence, effluent after tanning processes contains higher concentration of heavy metals. Though Cr(III) is less toxic than Cr(VI), there is higher possibility of oxidation during subsequent treatment processes. Therefore, several methodologies have been developed to remove the heavy metals from the effluent before processing it for common effluent treatment. Phytoremediation is one of the eco-friendly techniques to remove the heavy metals from soil and wastewater. It is commonly used to remediate the unfertilized lands to fertile lands for agriculture. Moreover, metal absorbed plants are used for various applications such as tanning and preservative agent in the leather industry. Hence, metal absorbed plants are not dumped as solid waste. Similarly, algae and fungi are used to remove the heavy metals from the tannery waste and can be as metal-polysaccharide auxiliary chemicals during post-tanning processes. Utilization of nonpathogenic bacteria is also used for the absorption of heavy metals. In this case, the handling of biomass is easier compared to other methodologies owing to less time duration and labor friendly, whereas, in the case of phytoremediation, absorption rate directly depends on the growth duration. In the present chapter, detailed case study is carried out to compare the advantages and disadvantages of various bioremediation technologies employed for treating leather wastewater.