School of Environmental Science and Engineering, Tianjin University, Tianjin, 300350, China.
School of Environmental Science and Engineering, Tianjin University, Tianjin, 300350, China; Tianjin Engineering Center of Urban River Eco-Purification Technology, Tianjin, 300350, China.
Environ Res. 2020 May;184:109007. doi: 10.1016/j.envres.2019.109007. Epub 2019 Dec 5.
High salinity suppresses denitrification by inhibiting microorganism activities. The shift of microbial community and denitrification functional genes under salinity gradient was systematically investigated in a biofilm electrode reactor (BER) and biofilm reactor (BR) systems. Denitrification efficiency of both BER and BR was not significantly inhibited during the period of low salinity (0-2.0%). As the salinity increased to 2.5%, BER could overcome the impact of high salinity and maintained a relatively stable denitrification performance, and the effluent NO-N was lower than 1.5 mg/L. High salinity (>2.5%) impoverished microbial diversity and altered the microbial community in both BER and BR. However, two genera Methylophaga and Methyloexplanations were enriched in BER due to electrochemical stimulation, which can tolerate high salinity (>3.0%). The relative abundance of Methylophaga in BER was almost 10 times as much as in BR. Paracoccus is a hydrogen autotrophic denitrifier, which was obviously inhibited with 1.0% NaCl. The hetertrophic denitrifiers were primarily responsible for the nitrate removal in the BER compared to the autotrophic denitrifiers. The abundance and proportion of denitrifying functional genes confirmed that main denitrifiers shift to salt-tolerant species (nirK-type denitrifiers) to reduce the toxic effects. The napA (2.2 × 10 to 6.5 × 10 copies/g biofilm) and nosZ (2.2 × 10 to 4.4 × 10 copies/g biofilm) genes were more abundant in BER compared to BR's, which was attributed to the enrichment of Methylophaga alcalica and Methyloversatilis universalis FAM5 in the BER. The results proved that BER had greater denitrification potential under high salinity (>2.0%) stress at the molecular level.
高盐度通过抑制微生物活性来抑制反硝化作用。本研究系统地研究了盐度梯度下生物膜电极反应器（BER）和生物膜反应器（BR）系统中微生物群落和反硝化功能基因的变化。在低盐度（0-2.0%）期间，BER 和 BR 的反硝化效率均未受到显著抑制。当盐度增加到 2.5%时，BER 能够克服高盐度的影响，保持相对稳定的反硝化性能，出水 NO-N 低于 1.5mg/L。高盐度（>2.5%）降低了微生物多样性并改变了 BER 和 BR 中的微生物群落。然而，电化学刺激使两个属甲基噬氢菌属（Methylophaga）和甲基杆菌属（Methyloexplanations）在 BER 中得到富集，它们能够耐受高盐度（>3.0%）。BER 中甲基噬氢菌属的相对丰度几乎是 BR 中的 10 倍。副球菌（Paracoccus）是一种氢自养反硝化菌，在 1.0%NaCl 下明显受到抑制。与自养反硝化菌相比，异养反硝化菌是 BER 中硝酸盐去除的主要贡献者。反硝化功能基因的丰度和比例证实，主要反硝化菌向耐盐物种（nirK 型反硝化菌）转变，以减轻毒性作用。与 BR 相比，BER 中的 napA（2.2×10 到 6.5×10 拷贝/g 生物膜）和 nosZ（2.2×10 到 4.4×10 拷贝/g 生物膜）基因更为丰富，这归因于 BER 中甲基噬氢菌属（Methylophaga alcalica）和甲基杆菌属（Methyloversatilis universalis FAM5）的富集。结果从分子水平证明了 BER 在高盐度（>2.0%）胁迫下具有更大的反硝化潜力。
