Treatability & Biogas Production Potential of Tannery Effluent in Anaerobic Sequential Batch Rectors from One of the Tannery Found in Addis Ababa, Ethiopia

Abstract

Direct discharge of tannery effluent to the surrounding water bodies affects the water quality and further causes reduction and death of aquatic fauna and flora. The effect can be minimized by treatment of tannery effluent prior to discharge to the environment. Biological treatment method is cost effective and environmentally friendly than physicochemical treatment method. The objective of this study was to develop a laboratory scale anaerobic sequence batch reactor and evaluate the treatment efficiency and biogas production potential of chrome tanning effluent at mesophilic (37ᴼC±2) system. The study was conducted at five treatments (wastewater containing different concentration of chrome). The treatments (T-1 to T-5) contain chrome concentrations (Cr³⁺) 185mg/l, 120mg/l, 14mg/l and 6.85mg/l for T-1, T-2, T-3, T-4, and T-5 respectively. The hydraulic retention time of all treatments was three days and five days, the organic loading rate was wide-ranging between 1.49 kg COD/m3 /day for T-1 to 1.32 kg COD/m³/day forT-5 throughout the study. The removal efficiency of TS and VS of all treatments were in the range of 52-69% and 58-81%, respectively. The removal efficiency of COD,BOD,TN, NO₃^- , S^-2, SO₄ ^-2, PO₄ ^3- and Cr³⁺ of all treatments were in the range of 42-62%,41-71%, 31-43%, 31-49%, 40-71%, 41-64%, 48-74% and 30-61% respectively. The maximum value of biogas at five days hydraulic retention time for (T-1 to T-5), (0.0089, 0.0097, 0.012, 0.027 and 0.034 m³ biogas/kg VS respectively) with methane content 21.1%, 22.7%, 37%, 51.3% and 54.7% was obtained after steady stable state condition. Hence, pretreated chrome tanning effluent with Cr (III) of 6.85mg/l was a potential feedstock for ASBR.

Keywords: Anaerobic sequential batch reactor, Chrome Tanning Effluent, Biogas

DOI: 10.7176/JETP/9-1-01