Synergistic suppression of nitrous oxide and residual nitrate in DNRA-enhanced MABR-PN/A hybrid systems
Jiao Yin1, Haotian Jiang1, Linhong Qiu1
1State Key Laboratory of Urban-rural Water Resource and Environment (SKLUWRE), Harbin Institute of Technology, 73 Huanghe Road, Nangang District, Harbin, 150090, PR China.
Abstract:
To resolve NO3--N production and accumulation in MABR coupled partial nitrification-Anammox (MABR-PN/A) for autotrophic nitrogen removal enhancement, an iron-carbon (IC) mediated NO3--N dissimilation system (IC-MABR-PN/A) was developed. Results indicate that when anaerobic ammonia oxidizing bacteria (AnAOB) are not added, IC-MABR-PN enhanced NO3--N dissimilation (reducing NO3--N by 11.86±0.68 mg/L vs. MABR-PN) due to nitrite dissimilation enzyme (Nrf) accumulation and stronger competition for NO2--N compared to nitrite reductase (Nir) under IC stimulation (2.23 log2). Besides, IC concurrently strengthened denitrification in IC-MABR-PN (TN decreased by 6.48±0.28 mg/L but N2O accumulation by 37.9 ± 5.8 μg/L vs. MABR-PN). Notably, when AnAOB was added to IC-MABR-PN, hydrazine synthase (Hzs, 1.83 log2) in IC-MABR-PN/A exhibited stronger binding affinity than nitric oxide reductase (Nor, -1.96 log2), favoring NO competition in IC-MABR-PN/A and suppressing N2O pathways (reducing its emissions to one-ninth of that in IC-MABR-PN). Anammox further regulated biofilm hydrophobicity to mitigate interfacial repulsion and iron-carbon-induced compaction, enhancing nitrogen transfer. The study achieved synergistic NO3--N removal and N2O reduction through IC-mediated NO3--N dissimilation and Anammox competition.
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