Nitrogen Removal from Dewatering Liquid of Landfill Sludge by a Two-Stage Anoxic/Oxic Membrane Bioreactor Via Partial Nitrification and Denitrification

Abstract

Two pilot-scale two-stage anoxic/oxic membrane bioreactors were operated at different dissolved oxygen (DO) levels to evaluate the nitrogen removal performances for treating landfill sludge dewatering liquid (SDL) via partial nitrification (PN) and denitrification. Compared to the low DO system (2.0 – 3.0 mg/L), the high DO system (5.0 – 6.0 mg/L) exhibited efficient PN and denitrification, with high nitrite accumulation efficiency (98.5%) and nitrogen removal efficiency (98.0%). The high DO system removed nitrogen mainly via PN (53.8%) and simultaneous nitrification and denitrification (45.1%). Kinetic inhibition tests verified the optimal DO and pH at 5.0 mg/L and 8.5. Enriched nitrifying (Nitrosomonas) and denitrifying bacteria (Thiopseudomonas, Pseudomonas, and Truepera) in the high DO environment accomplished the nitrogen removal process. Metagenomic analysis showed that the high DO system enriched functional genes such as amoA/B/C, hao, and nirK/S, while the low DO system was unsuitable for PN of high ammonia nitrogen wastewater.

Keywords: landfill sludge dewatering liquid, partial nitrification and denitrification, two-stage anoxic/oxic membrane bioreactor, dissolved oxygen, free ammonia