Scope of biological treatment for composite tannery wastewater

Tannery wastewater is heavily polluted containing appreciable biodegradable matters as well as inorganic substances like chromium, sulphide, chloride etc. Thus the composite tannery wastewater appears to be incompatible for direct biological treatment .Wastewater emanated from various sub-processes of tannery operation showed variable characteristics and also differential treatability. The present paper reviews the literature on the characteristics of wastewater generated from chrome tannery units and the treatment of the same. The treatment processes earlier used for tannery wastewater were physico-chemical methods or biological methods or combination of physico-chemical and biological methods. However biological methods were employed mainly for a few sub processes generating significant organic matter and without chromium, chlorides etc. In view of rapid development in biological processes, emphasis is now being given to treat the composite tannery wastewater exclusively by a well acclimated consortium of microbial species .As a result biological recovery of valuable chromium has been envisaged rather than chemical method to reduce the overall cost of treatment. The present paper also highlights on the methods available for biological treatment of composite tannery wastewater. In this regard the scope of hybrid bioreactor an advanced technology option has also been explore as this kind of treatment is well situated for the wastewater having inhibitory substances.