Anaerobic digestion is a favorable technological solution which degrades a substantial part of the organic matter contained in the sludge and tannery solid wastes, generating valuable biogas, contributing to alleviate the environmental problem, giving time to set-up more sustainable treatment and disposal routes. Digested solid waste is biologically stabilized and can be reused in agriculture.
The application of an anaerobic treatment for the break down of COD from tannery waste water is an attractive method to recover energy from tannery wastewater. Until now it was considered that the complexity of the waste water stream originating from tanneries in combination with the presence of chroming would result in the poisoning of the process in a high loaded anaerobic reactor.
When the locally available industrial wastewater treatment plant is not provided by anaerobic digester, a large scale digestion can be planned in regions accommodating a big cluster of tanneries, if there is enough waste to make the facility economically attractive. In this circumstance, an anaerobic co-digestion plant based on sludge and tanneries may be a recommendable option, which reduces the quantity of landfilled waste and recovers its energy potential. It can also incorporate any other domestic, industrial or agricultural wastes. Chrome-free digested tannery sludge also has a definite value as a fertilizer based on its nutrient content.