Long-term nitrogen removal performance and kinetics of anaerobic ammonia oxidation bacteria treating nitrogen-rich saline wastewater with trehalose addition

A sequencing batch reactor was used to study long-term nitrogen removal performance of anaerobic ammonia oxidation bacteria (AnAOB) with trehalose addition treating nitrogen-rich saline wastewater. The operating temperature was controlled at 35 +/- 0.5 degrees C with influent pH of 7.5 +/- 0.1. Trehalose played a significant role in enhancing long-term nitrogen removal performance. When trehalose was 0.1, 0.2, and 0.3 mM, ammonia removal efficiency (ARE) increased by 4.9%, 16.2%, and 32.4%, and nitrite removal efficiency (NRE) improved by 7.5%, 27.9%, and 42.2%, respectively. Optimal ARE and NRE were 92.4% and 97.4% achieved at 0.35 mM trehalose. Moreover, NO2--N was removed completely within 2 hr at high trehalose content due to the synergistic effect resulting from AnAOB and heterotrophic denitrifying bacteria. Delta NO2--N/Delta NH4+-N increased with trehalose addition, while Delta NO3--N/Delta NH4+-N decreased. Compared to Delta NO3--N/Delta NH4+-N, Delta NO2--N/Delta NH4+-N fluctuated greatly. The remodified Logistic model and modified Gompertz model were suitable for describing nitrogen removal in an operating cycle with trehalose addition. Fitted ARE(max) values were consistent with experimental values. Appropriate trehalose addition could shorten the response time of AnAOB coping with hazardous environment stress. Lag time was within 1 hr and the minimal fitted lambda value got close to 0 achieved at 0.15 mM trehalose. Practitioner points Trehalose enhanced nitrogen removal of AnAOB in saline wastewater treatment. Optimal ARE and NRE were 92.4% and 97.4% achieved at 0.35 mM trehalose. Remodified Logistic and Gompertz models can analyze nitrogen removal with trehalose. Appropriate trehalose can shorten response time of AnAOB coping with salt stress.