(homoacetogenic bacteria) only occurred under certain conditions similarly played only a small part in CO2 accumulation15. As the changes of hydrogenotrophic methanogens and homoacetogenic bacteria groups only modestly affect CO2 consumption. Therefore, the inhibition of aceticlastic methanogens was the best explanation for the decrease in CO2 production.
Overall, the TC removal rate was 14.97–67.97% in the reactor. TC had a large negative effect on CH4 and CO2 generation, which caused a large decrease of total biogas production. However, the presence of TC apparently had a positive effect on H2 and VFAs accumulation. All this responses indicated that the methanogenesis process was sensitive to TC presence, but the acidogenesis process was insensitive. This suggests that the presence of TC had less influence on the degradation of organic matter but had a strong influence on CH4 and CO2 generation. The reduced CH4 and CO2 production is beneficial for emission reduction in anaerobic wastewater treatment, which can alleviate the greenhouse effect and global warming. Additionally, additional electricity can be produced from the additional H2 and VFAs accumulation, which can help reduce the use of fossil fuels. Also, VFAs can be used as raw materials for production of higher added value fermentation products. Overall, the promoted H2 and VFAs accumulation can provide higher added values for resource recovery54–57, which is good for energy-saving. Regardless of the inhibition of mechanism, the presence of TC in wastewater provides a new point of view for energy-saving and emission reduction in anaerobic wastewater treatment. Therefore, methods can be used in anaerobic wastewater treatment to avoid the negative effects of TC and benefit from TC’s positive effects.