Analysis of methane production inhibition for treatment of sewage sludge containing sulfate using an anaerobic continuous degradation process

−The inhibition of methane production in the continuous anaerobic degradation process for the treatment of sewage sludge containing sulfate was investigated. Also, the competition between sulfate-reducing bacteria (SRB) and methane-producing bacteria (MPB) with COD/sulfate ratio was explained in terms of electron flow. The methane production rate was 0.07, 0.13, 0.24, 0.31 and 0.33 l-CH4 g-COD when the initial COD/sulfate ratio was 3.3, 5.0, 6.7, 10 and 20, respectively. The numbers of SRB and MPB were counted after the continuous reactor reached steady state and the two bacteria showed opposite growth behaviors with COD/sulfate ratio. The inhibition by sulfate compounds was found to follow the uncompetitive model and inhibition constants were 24.57 and 87.99 mg l for SRB and MPB, respectively. These results can be useful data for the efficient treatment of sewage sludge in a continuous anaerobic degradation process.