Green Energy from the Combined Treatment of Liquid and Solid Waste from the Tanning Industry Using an Upflow Anaerobic Sludge Blanket Reactor

Abstract

During leather processing about 30–50 m3 of tannery effluent (TE) and 150–250 kg of limed fleshings (LF) are generated for every tonne of hides or skins processed. Currently, TE is treated in an individual or common effluent treatment plant, and solid wastes are disposed of without treatment, leading to emission of greenhouse gases. In the present study, an innovative approach of treating limed fleshings after liquefaction (LLF) and TE together in an upflow anaerobic sludge blanket (UASB) reactor has been carried out for generation of green energy in the form of biogas with methane. Further, the effect of the organic loading rate (OLR) on chemical oxygen demand (COD) removal and methane yield has been investigated in an UASB reactor. On the basis of the present study, the maximum COD removal efficiency of 75% with a methane yield of 0.29 m3/kg of COD removed at an optimum OLR of 12 kg m–3 day–1 and hydraulic retention time (HRT) of 24 h was obtained. This innovative approach of combined treatment resulted in an additional methane yield of 37.5% when compared to the methane yield from treatment of tannery wastewater alone in an UASB reactor. Certified emission reductions (CERs) generated have been estimated for combined treatment of TE and LLF in an UASB reactor by replacing open dumping of fleshings for a typical tannery cluster.