Anaerobic treatment of tannery wastewater with simultaneous sulphide elimination

Sulphide is known as an inhibiting substance in anaerobic microbial processes. The objective of this research was to examine sulphide inhibition in batch and continuous culture experiments. A real wastewater of leather production was used which contained high sulphide and low sulphate concentrations. Thus the observed inhibition resulted from direct toxicity of sulphide on bacteria. Trace element precipitation and substrate competition between sulphate reducing and methane producing bacteria were of negligible influence. In batch experiments gas production was delayed with increased sulphide concentrations. A stripping system was integrated in a laboratory reactor to eliminate sulphide and to improve the efficiency of degradation. In a continuous flow fixed film reactor the concentration of 100 mg l−1 undissociated sulphide inhibited the efficiency and degree of degradation. This inhibition was eliminated by a simultaneous sulphide stripping system which reduced the concentration of undissociated sulphide to 30 mg l−1. The efficiency of degradation was improved by 15% at a hydraulic retention time of 1.9 days.