[Effect of Salinity on Nitrogen Removal Performance of a Pilot-scale Anaerobic Ammonia Oxidation Process and Its...

The denitrification characteristics of anaerobic ammonia oxidizing bacteria (AnAOB) treating high salinity wastewater were investigated in an pilot-scale anaerobic sequencing batch reactor (ASBR, 530 L) by gradually increasing the Cl^- concentration. The results showed that AnAOB can adapt to the high salinity (Cl^- concentration of 10000 mg·L^-1) environment for high-efficiency denitrification by means of gradual salinity acclimation and total nitrogen (TN) removal rate of up to 92.3%. In particular, the denitrification performance was influenced by two gradients of Cl^- concentrations, namely 6000 mg·L^-1 and 10000 mg·L^-1, but it could be gradually recovered as the acclimatization process continued. The modified Boltzmann model accurately fit the activity recovery process of AnAOB after being inhibited by the different salinities, and the correlation coefficient R² was above 0.96. The fitted recovered median values t_c for Cl^- concentrations of 6000 mg·L^-1 and 10000 mg·L^-1 were 28.765 d and 44.495 d. NRR_max for these concentrations was 0.145 kg·(m³·d)^-1 and 0.212 kg·(m³·d)^-1, and NRR_min was 0.021 kg·(m³·d)^-1 and 0.085 kg·(m³·d)^-1, respectively. After salinity acclimation, the dominant bacteria of AnAOB were Candidatus Brocadia and Candidatus Jettenia (the abundances were 14.76% and 2.7%, respectively), the granulation degree and sludge density increased to varying degrees, and the sludge color was reddish brown.