Initiation and Recovery of Nitrosation in Zeolite Bioreactors

Abstract

Stable partial nitrosation is important for processes based on anaerobic ammonia oxidation. In this study, an up-flow sludge fixed-bed reactor filled with natural zeolites at the bottom was used, under the condition that no organic carbon source is added, after gradually increasing the influent ammonia nitrogen load (ALR). At d 21, stable partial nitrosation was successfully initiated. The results showed that the influent ammonia nitrogen load was 0.5451 kg/(m3 d) at an HRT of 16 h. The nitrite accumulation rate (NAR) of the system was 91.52% at this time, and the nitrite yield was 0.2384 kg/(m3 d), and the effluent met the anaerobic ammonia oxidation influent requirements. After reducing the influent ammonia nitrogen concentration to 250 mg/L, the system nitrosation stability was disrupted and the NAR dropped to a minimum of 21.35%, but after restoring the influent ammonia nitrogen concentration, the system NAR was restored to 92.79% after only 6 d. The inhibition of nitrite oxidising bacteria (NOB) by ammonia nitrogen loading is an important reason why stable nitrification is achieved. Zeolite dosing allows the system to quickly recover nitrosation performance when the influent ammonia nitrogen concentration fluctuates. Stable partial nitrosation anaerobic ammonia oxidation process laid the foundation for stable application in engineering.