Behavior of the anaerobic treatment of tannery wastewater at different initial pH values and sulfate concentrations

The influence of initial pH and sulfate concentration on the anaerobic digestion of tannery wastewater was studied using the specific methanogenic activity (SMA) test. The SMA tests were performed with a chemical oxygen demand (COD) concentration of 6.5 g/L and SO^-2₄ concentrations of 1.95, 3.90, 6.50, 8.45 and 10.4 g/L. The effect of pH was studied at pH 6.8; 6.4 and 6.1. It was found that methane production took place under all conditions, but the use of SO^-2₄ concentrations higher than 8.45 g/L and initial pH levels lower than 6.4 caused a decrease of up to 73% of methane production. The influence of pH was significant only for SO ^-2₄ concentrations lower than 8.45 g/L, with up to 50% inhibition. Specific methanogenic activity for COD/SO^-2₄ ratios lower than 0.77 depends basically on this ratio and not on the initial pH value under the conditions of the study.