Complex inhibitions on anaerobic degradation of monosodium glutamate in wastewater under low COD/sulfate ratios

To investigate the complex inhibitions leading to the deterioration of reactor performance in anaerobic treatment of monosodium glutamate (MSG) wastewater under low COD/sulfate ratios, a comprehensive assessment of the overall reactor performance, sludge characteristics and microbial community characteristics was conducted in this study. The COD removal rate of the reactor was maintained above 90% throughout the experiment, but the gas yield decreased by 52% due to the complex competition between sulfate-reducing bacteria (SRB) and methane-producing archaea (MPA) resulting in a decreasing number of MPA. The sludge characteristics and microbial community features indicated that the complex competition between SRB and MPA included competition for hydrogen and survival space in the reactor. In addition, the competitive advantage of SRB for electrons led to the production of more sulfides in the reactor, further inhibiting the activity of MPA. Therefore, the complex inhibition within the reactor for anaerobic treatment of MSG wastewater with low COD/sulfate ratios, including sulfide toxicity inhibition, competition between SRB and MPA for substrate and space, not only led to a reduction in gas production, but also affected microbial activity and glutamate degradation.