Linking ecological niche and metabolic hierarchy in low-oxygen-driven anammox systems

Abstract

Dissolved oxygen (DO) is regarded as a key regulatory factor for the practical engineering applications of anaerobic ammonium oxidation (anammox) processes, however, the adaptability and metabolic mechanisms of floc anammox consortia with low-oxygen as potential substrates involved in the holistic microbial metabolic system are still elusive. This study showed that the nitrogen removal efficiency (NRE) of floc anammox consortia was 16.45% and 35.71% higher at DO of 0.2–0.5 mg·L−1 than at DO <0.2 mg·L−1 and DO of 0.5–0.8 mg·L−1, respectively. Meanwhile, the activity of anammox bacteria (AnAOB) and ammonia-oxidizing bacteria (AOB) was the highest, representing 22.64 ± 3.20 mg N·g−1 V SS·d−1 and 103.22 ± 6.47 mg N·g−1 VSS·d−1, respectively. AnAOB applied the antioxidant enzymes (CCP, T-SOD) and Cbb3-type cytochrome c oxidase (Cbb3-type CcO) for oxygen detoxification and utilization. Moreover, AOB, aerobic/anoxic heterotrophic bacteria, denitrifying bacteria, etc. defined as the core members in anammox consortia could also consume DO and adjust the NH4+-N/NO2−-N ratio for AnAOB, establishing potent microbial interactions to relieve the pressure of DO on AnAOB and improve NRE. This study reveals that anammox consortia can utilize limited DO as a substrate to promote anammox processes, which advances the practical applications of anammox processes.