Whether glycine betaine improves the thermotolerance of mesophilic anammox consortia.

While the application of mesophilic anammox process is currently the state of the art, the feasibility of a thermophilic anammox bioprocess is still unclear. In this study, we investigate whether glycine betaine (GB) addition can enhance the thermotolerance of mesophilic anammox biomass in the upflow anaerobic sludge blanket (UASB) reactors fed with synthetic wastewater at a nitrogen loading of approximately 4 kg N m d. The results showed that during a long-term operation at 45°C with GB (0, 0.1, 1, 2 mM) addition, anammox performance became worse with the final effluent concentrations of NO N of 145 ± 11.6 mg L and nitrogen removal efficiency decreased from 92.3-6.9%. Specific anammox activity decreased from 392.1 ± 12.1-6.0 ± 0.8 mg N g VSS d, which were not significantly higher than those in the control reactor. The content of heme c showed a stronger downward trend in T (with GB addition) than in the control reactor T. The qPCR results showed that the relative abundance of Kuenenia decreased in both the experimental (from 53.5-28.8%) and control reactors (from 54.1-35.1%). Overall, continuous addition of exogenous GB did not improve the thermotolerance of mesophilic anammox consortia at 45°C.