External organic carbon sources are needed to provide electron donors for the denitrifica-tion of wastewater with a low COD/NO3-N (C/N) ratio,increasing the treatment cost.The economic strategy is to enhance the bioactivity and/or biodiversity of denitrifiers to effi-ciently utilize organic substances in wastewater.In this study,novel zero-valent iron (ZVI)composite carriers were prepared and implemented in a suspended carrier biofilm reactor to enhance the bioactivity and/or biodiversity of denitrifiers.At the influent C/N ratio of 4 (COD was 179.5 ± 5.0 mg/L and TN was 44.2 ± 0.8 mg/L),COD and TN removal efficiencies were 85.1％ and 66.4％,respectively,in the reactors filled with 3 wt％ ZVI composite carriers.In contrast,COD and TN removal efficiencies were 70.4％ and 55.3％,respectively,in the reactor filled with conventional high-density polyethylene (HDPE) biofilm carriers.The biofilm for-marion on the 3 wt％ ZVI composite carriers was optimized due to its higher roughness (sur-face square roughness increased from 76.0 nm to 93.8 nm) and favorable hydrophilicity (wa-ter contact angle dropped to 72.5° ± 1.4° from 94.3° ± 3.2°) compared with the H-DPE biofilm carriers.In addition,heterotrophic denitrifiers,Thauera and Dechloromonas,were enriched,whereas autotrophic denitrifiers,Raoultella and Thiobaeillus,exhibited high relative abun-dance in the biofilm of ZVI composite carriers.The coexistence of heterotrophic denitrifiers and autotrophic denitrifiers on the surface of ZVI composite carriers provided mixotrophic metabolism of denitrification (including heterotrophic and iron-based autotrophic),thereby ensuring effective denitrification for wastewater with a low C/N ratio without external or-ganic carbon source addition.

Yanping Shi;Tao Liu;Hongtao Yu;Xie Quan

Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education),School of Environmental Science and Technology,Dalian University of Technology,Dalian 116024,China

环境科学学报（英文版）

[1]Yanping Shi;Tao Liu;Hongtao Yu;Xie Quan-.Enhancing anoxic denitrification of low C/N ratio wastewater with novel ZVI composite carriers)[J].环境科学学报（英文版）,2022(02):180-191

denitrifica,denitrifiers,marion,Thiobaeillus,mixotrophic

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