Performance and microbial community analysis of a novel DEAMOX based on partial-denitrification and anammox treating ammonia and nitrate wastewaters

In this study, a novel DEAMOX (DEnitrifying AMmonium OXidation) process coupling anammox with partial-denitrification generated nitrite (NO₂^--N) from nitrate (NO₃^--N) was developed for simultaneously treating ammonia (NH₄⁺-N) and NO₃^--N containing wastewaters. The performance was evaluated in sequencing batch reactors (SBRs) with different carbon sources for partial-denitrification: acetate (R1) and ethanol (R2). Long-term operation (180 days) suggested that desirable nitrogen removal was achieved in both reactors. The performance maintained stably in R1 despite the seasonal decrease of temperature (29.2 °C-12.7 °C), and high nitrogen removal efficiency (NRE) of 93.6% on average was obtained with influent NO₃^--N to NH₄⁺-N ratio (NO₃^--N/NH₄⁺-N) of 1.0. The anammox process contributed above 95% to total nitrogen (TN) removal in R1 with the nitrate-to-nitrite transformation ratio (NTR) of 95.8% in partial-denitrification. A little lower NRE was observed in R2 with temperature dropped from 90.0% at 22.7 °C to 85.2% at 16.6 °C due to the reduced NTR (87.0%-67.0%). High-throughput sequencing analysis revealed that Thauera genera were dominant in both SBRs (accounted for 61.53% in R1 and 45.17% in R2) and possibly played a key role for partial-denitrification with high NO₂^--N accumulation. The Denitratisoma capable of complete denitrification (NO₃^--N→N₂) was found in R2 that might lead to lower NTR. Furthermore, different anammox species was detected with Candidatus Brocadia and Candidatus Kuenenia in R1, and only Candidatus Kuenenia in R2.