Autotrophic nitrogen removal by partial nitrification-anammox process in two-stage sequencing batch constructed wetlands for low-strength ammonium wastewater

In this study, partial nitrification-anammox process was established in two-stage sequencing batch constructed wetlands (SBCWs) to achieve autotrophic nitrogen removal for low-strength ammonium wastewater treatment. The operational parameters of the partial nitrification process were investigated and optimized, for the subsequent anammox process. The results indicated idle time and reaction time had significant influences to partial nitrification SBCW (WPN). In the WPN with optimal condition (idle time = 7.5 h, reaction time = 16 h), the effluent nitrite to ammonium ratio (NO2-N/NH4+-N) remained stable at 1.24 +/- 0.09, which favored the anammox process. The anammox SBCW (WAmx) was established rapidly within 61 d. The two-stage SBCWs showed high efficient nitrogen removal capacity, with effluent total nitrogen (TN) concentration of 3.89 +/- 0.62 mg/L and TN removal rate of 81.11 +/- 2.92 %. Moreover, high-throughput sequencing revealed that Nitrosomonas (37.5 %) was dominant under optimal condition in WPN and responsible for partial nitrification process. Candidatus Brocadia (26.5 %) was enriched in WAmx, undertaking anammox process with synergism of flanking bacteria. This study provides a sustainable alternative for low-strength wastewater treatment.