Qiang Li,Yuehui He,Boyan Wang,Nanhai Weng,Lei Zhang,Kaichun Wang,Fengrong Tian,Mingsheng Lyu,Shujun Wang
The biological denitrification of low-C/N wastewater is a great challenge in treatment plants due to the lack of microorganisms with heterotrophic nitrification–aerobic denitrification (HN-AD) abilities. In this study,Bacillussp. L2 was isolated from aeration tank water samples using a nitrification medium and screened for its ability to perform HN-AD in low-C/N wastewater. The strain showed a maximum NH4+-N removal rate of 98.37% under low-C/N conditions. In the presence of a mixed N source, strain L2 was capable of completely removing NH4+-N within 24 h. Furthermore, optimal nitrogen removal conditions for strain L2 were found to be C/N = 9, pH = 9, and sodium acetate as the C source. Under optimal conditions, the strain was able to maintain a high NH4+-N removal rate under 0–3% salinity and an NH4+-N concentration of 200 mg/L or less. The denitrification pathways of strain L2 were NH4+→NH2OH→NO2−(↔NO3−)→NO→N2O→N2and NH4+→NH2OH→NO→N2O→N2. Furthermore, semi-continuous wastewater treatment was conducted using immobilized technology, which resulted in more than 82% NH4+-N removal after three cycles of reuse. This study demonstrates the great potential ofBacillussp. L2 in wastewater treatment applications.
An innovative partial nitrification and short-cut sulfur autotrophic denitrification (PN-SSAD, NH 4 + -N → NO 2 − -N → N 2 ) coupled system in a single-stage SBR was proposed to treat low C/N wastewater with low material and energy consumption. Nearly 50 % alkalinity consumption and 40 % sulfate production were reduced in S 0 -SSAD compared with S 0 -SAD, whereas the autotrophic denitrification rate was increased by 65 %. In S 0 -PN-SSAD, the TN removal efficiency reached almost 99 % without additional organic carbon. Furthermore, pyrite (FeS 2 ) rather than S 0 served as the electron donor to optimize the PN-SSAD process. The practical sulfate production in S 0 -PN-SSAD and FeS 2 -PN-SSAD were about 38 % and 52 % lower than complete nitrification and sulfur autotrophic denitrification (CN-SAD), respectively. Thiobacillus was the major autotrophic denitrification bacteria in S 0 -PN-SSAD (34.47 %) and FeS 2 -PN-SSAD (14.88 %). Nitrosomonas and Thiobacillus played a synergistic effect in the coupled system. FeS 2 -PN-SSAD is expected as an alternative technology for nitrification and heterotrophic denitrification (HD) in treating low C/N wastewater.
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