Advanced nitrogen removal from real municipal wastewater by multiple coupling nitritation, denitritation and endogenous denitritation with anammox in a single suspended sludge bioreactor

Achieving advanced nitrogen removal based on anammox for treating mainstream municipal wastewater in a single suspended sludge bioreactor is a challenging research topic. In this study, multiple coupling nitritation, denitritation and endogenous denitritation with anammox (PNA-(E)PDA) was simultaneously achieved in a 10 L step-feed bioreactor, which enhanced stable nitrogen removal. After 223 days of operation, the total nitrogen concentrations of the influent and effluent were 70.7 +/- 6.1 and 4.3 +/- 1.8 mg/L, respectively, when treating municipal wastewater even at C/N ratio of 2.24 with only 5 h of aerobic time (DO: 0.5-0.8 mg/L). After the evolution of nitritation/anammox to PNA-(E)PDA, the contribution of anammox to nitrogen removal increased to 78.6% and the anammox activity increased from 4.3 +/- 0.2 to 15.2 +/- 0.7 mg NH4+-N/gVSS/d. qPCR results showed that the abundance of anammox bacteria increased from 4.1 x 10(9) to 4.5 x 10(10) copies/ (g VSS). Highthroughput sequencing further revealed that the relative abundance of Candidatus Brocadia, the dominant anammox genus, increased from 0.09 to 0.46%. Based on the strong competitiveness of anammox on nitrite, this novel PNA-(E)PDA process provides a potential strategy for enriching anammox bacteria in municipal wastewater treatment plants.

Automated summary

This study successfully achieved multiple coupling nitritation, denitritation, and anammox in a 10 L bioreactor, enhancing stable nitrogen removal. After 223 days of operation, anammox activity and abundance increased significantly, providing a potential strategy for enriching anammox bacteria in wastewater treatment plants.