Cultivation and Performance Analysis of Simultaneous Partial Nitrification, ANAMMOX, and Denitratation Granular Sludge

Abstract

We cultivated simultaneous partial nitrification, anaerobic ammonium oxidizing(ANAMMOX), and denitratation granular sludge in a novel air-lift internal circulation reactor using low C/N wastewater as the substrate and ANAMMOX sludge matched with ordinary activated sludge as the inoculum. The results showed that the mature and stable granular sludge could be cultivated after 225 d of continuous operation, and the total nitrogen removal rate was as high as 91.4%. Compared with flocculated sludge, the ANAMMOX activity in the granular sludge increased significantly, and the ANAMMOX activity was highest among the four nitrogen removal processes followed by partial nitrification, and the specific denitratation activity was 2.1-times higher than the specific nitrite reduction activity. High-throughput sequencing results showed that the dominant bacteria in partial nitrification and ANAMMOX were Nitrosomonas and Candidatus_Brocadia, respectively, compared to flocculated sludge, with abundances increasing to 0.70% and 0.57%, respectively. Thauera may also be the potential dominant bacteria for denitratation, with an abundance of up to 0.26%. RT-qPCR analysis showed that compared to the inoculation stage, the transcript levels of the amoA and hao genes for partial nitrification increased 3.5-and 1.5-fold, respectively, and the transcript levels of the hzsA gene for ANAMMOX increased 2.1-fold. During denitrataion, the overall abundance of napA and narG transcript levels was 4.8-times higher than that of nirK and nirS. The results of this study provide new insights for the treatment of low C/N wastewater.