Reactor performance and microbial community structure of single-stage partial nitritation anammox membrane bioreactors inoculated with Brocadia and Scalindua enrichment cultures

Partial nitritation combined with anaerobic ammonium oxidation (anammox), hereafter referred to as PNA, is a promising biological nitrogen-removal process for ammonia-rich wastewater; however, the PNA application process to low-strength ammonia wastewater (i.e., mainstream anammox) remains challenging. In this study, two single-stage PNA processes using a membrane bioreactor (MBR) inoculated with the anammox enrichment culture of Candidatus Brocadia sinica (Brocadia-MBR) or Candidatus Scalindua sp. (Scalindua-MBR) were operated for low-strength ammonia wastewater treatment. Single-stage PNA process was established in both MBRs, showing rates of total nitrogen (TN) removal from 0.58 g-N L-1 day(-1) to 0.66 g-N L-1 day(-1), and 81%-89% TN-removal efficiency under optimal dissolved oxygen. Microbial community analysis showed that three ammonia-oxidizing bacteria (AOB), one nitrite-oxidizing bacteria (NOB), one Candidatus Brocadia were detected in the Brocadia-MBR, whereas one AOB, no NOB, and one Candidatus Scalindua were detected in Scalindua-MBR. The operational conditions in this study resulted in the out competition of anammox bacteria in both MBRs.

Automated summary

Partial nitritation combined with anaerobic ammonium oxidation (PNA) is a promising biological nitrogen-removal process for ammonia-rich wastewater, but its application to low-strength ammonia wastewater remains challenging. This study found that the single-stage PNA processes in two MBRs showed good total nitrogen removal, but competition among anammox bacteria was a concern in both systems.