Enhanced nitrogen removal of single stage partial nitritation anammox system by glycine betaine addition at low temperature: Performance and mechanism

Low activity of anaerobic ammonia oxidizing bacteria (AnAOB) at low temperature is still an obstacle to the application of a single stage partial nitritation anammox (SPNA) process. In order to improve the performance of nitrogen removal of this system at low ambient temperature, the glycine betaine (GB) was added into a continuous stirred tank reactor (CSTR) at 13-15 degrees C. At 15 degrees C, the nitrogen removal rate (NRR) was increased from 0.48 to 0.62 g N/(L.d) by adding 1 mM GB with the nitrogen loading rate of 0.81 g N/(L.d). The activity of hydrazine oxidase (HZO) was enhanced from 15.78 to 19.81 mu mol Cyt-c/(g VSS.min), while the extracellular polymeric substances (EPS) production was reduced from 290.31 to 109.06 mg/g VSS after exogenous GB. When the temperature was <15 degrees C, however, the promoting effect of 1 mM GB was weakened, and the NRR was 0.43 g N/(L.d) at 13 degrees C. Increasing the addition of GB to 1.5 mM did not improve nitrogen removal performance at 13 degrees C, whereas it promoted the enrichment of heterotrophic bacteria (HB). Overall, results suggested GB had the potential to enhance the metabolic capability of AnAOB, which provided a novel strategy for improving the nitrogen removal performance of SPNA system at low temperature.

Automated summary

The addition of glycine betaine was found to improve the performance of a single stage partial nitritation anammox system at low temperature, including enhancing the nitrogen removal rate and the activity of hydrazine oxidase, while reducing the production of extracellular polymeric substances. However, the promoting effect of glycine betaine weakened at lower temperatures and promoted the enrichment of heterotrophic bacteria.