Improved on Nitrogen Removal of Anaerobic Ammonia Oxidation by Coupling Element Sulfur-based Autotrophic Short-cut Denitrification

Abstract

In order to enhance the removal of NO3--N in the ANAMMOX process, an element sulfur-based autotrophic short-cut denitrification (short-cut S0-SADN) was introduced by adding elemental sulfur to an ANAMMOX continuous flow reactor. The effects of different influent NH4+-N/NO2--N ratios on the nitrogen conversion and NO2--N competitive characteristics in the coupled system were investigated at (33±2)℃ and a pH of 7.8-8.2. The results showed that under different influent NH4+-N/NO2--N ratios (1:1.3, 1:1.5, 1:1, and 1:1.1), the average total nitrogen (TN) removal efficiency of the coupled system reached 96.78%, 97.21%, 94.68%, and 97.72%, respectively, which were much higher than the highest TN removal efficiency of the ANAMMOX theory (89%). Among them, the stable operation of deep nitrogen removal of the short-cut S0-SADN coupled with ANAMMOX was successfully achieved with an influent NH4+-N/NO2--N ratio of 1:1 or 1:1.1. Under the optimal influent NH4+-N/NO2--N ratio of 1:1.1, the concentrations of influent NH4+-N and NO2--N were 240 mg·L-1 and 265 mg·L-1, respectively, the TN removal rate reached 1.50 kg·(m3·d)-1, and the TN removal efficiency of ANAMMOX and S0-SADN pathways were stable at (95.68±1.22)% and (2.04±0.77)%, respectively. During the entire operational process, ANAMMOX always occupied an absolute advantage in the competition of substrate NO2--N, and the activity of ANAMMOX bacteria (NH4+-N/VSS) was stable at (0.166±0.008)kg·(kg·d)-1.