Abstract
MSWI leachate contain high concentrations of ammonium nitrogen (NH4+-N). The conventional submerged air-diffusing (CSA) system are the dominant oxygen supply in the aerobic process for NH4+-N removal from leachate. However, it carries high energy consumption. In this study, Pure oxygen (PO), which is more environmentally friendly, was used as an alternative to air for solving this problem. For comprehensive analysis the effects of PO supersede air on nitrogen removals and microbial diversities in the aerobic process during treatment of MSWI leachate, two parallel full-scale anoxic-oxic systems were set with the floating Praxair's in situ oxygenation (I-SO™) system and the CSA system, respectively. Compared to the CAS system, the removal efficiency of total nitrogen (TN) increased by 9.79% with the I-SO™ system but COD and NH4+-N removals reduced by 6.83% and 1.19%, respectively. Metagenomic studies revealed that the bacterial richness, diversity, and evenness decreased with PO aeration, while the abundances of ammonia-oxidizing bacteria (AOB) and denitrifying bacteria (DNB) increased, as well as the AOB/nitrite-oxidizing bacteria (NOB) ratios. In addition, the nitrite-denitrification functional genes (nirK and nirS) deposited from autotrophic and Heterotrophic bacteria were more predominant and accounted for the higher efficiency of TN removal in the PO aeration treatment, while complete nitrification and nitrate-denitrification were dominant in the air aeration anoxic-oxic system. Therefore, nitrogen removal from MSWI leachate by using PO aeration provided theoretical perspective for engineering applications.
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