Impact of Ecological Factors on Anaerobic Ammonia-Oxidizing Bacteria Enrichments

Abstract

Anaerobic ammonia-oxidizing bacteria (AnAOB) have remarkably strong ability of coupling ammonia and nitrite into nitrogen gas and have been regarded as one of the most promising techniques for wastewater nitrogen removal. However, these anaerobic autotrophs are vulnerable to some environmental factors such as dissolved oxygen (DO), organic carbon, or antibiotics, which are inevitable in actual sewage or industrial wastewater. From an ecological perspective, the factors may not directly inhibit AnAOB but stimulate side populations. In this sense, it is necessary to understand the specific responses of AnAOB competitors to certain ecological factors (EFs). To date, most studies have only focused on direct effects of EFs to AnAOB but have not considered side populations. In this study, the impact of five EFs (DO, carbon, metal ion, antibiotics, and temperature) on AnAOB enrichments was assessed in a mixed-culture anammox reactor, which contained AnAOB, aerobic ammonia-oxidizing bacteria (AeAOB), nitrite-oxidizing bacteria (NOB), and denitrifying bacteria. Batch test results showed that oxygen did not inhibit AnAOB due to the protection of AeAOB and NOB, and both inorganic and organic carbon (acetate) enhanced AnAOB activity. Low concentration (0.04 mM) of iron was beneficial to AnAOB and AeAOB, but AnAOB were inhibited by a high concentration (0.26 mM) of iron. The tolerance of AnAOB enrichments to chloramphenicol was much stronger than that to amoxicillin and oxytetracycline. Temperature is a critical EF to AnAOB enrichments.