Fu Qizi, Long Sha, Xu Yunhao, Wang Yan, Yang Bentao, He Dandan, Li Xuemei, Liu Xuran, Lu Qi, Wang Dongbo
College of Environmental Science and Engineering and Key Laboratory of Environmental Biology and Pollution Control (Ministry of Education), Hunan University, Changsha 410082, PR China.
Zhongye Changtian International Engineering Co., Ltd., Changsha 410205, PR China.
J Hazard Mater. 2023 Jun 15;452:131305. doi: 10.1016/j.jhazmat.2023.131305. Epub 2023 Mar 28.
Free ammonia (FA), the unionized form of ammonium, is presented in anaerobic fermentation of waste activated sludge (WAS) at high levels. However, its potential role in sulfur transformation, especially HS production, during WAS anaerobic fermentation process was unrecognized previously. This work aims to unveil how FA affects anaerobic sulfur transformation in WAS anaerobic fermentation. It was found that FA significantly inhibited HS production. With an increase of FA from 0.04 to 159 mg/L, HS production reduced by 69.9%. FA firstly attacked tyrosine-like proteins and aromatic-like proteins in sludge EPSs, with CO groups being responded first, which decreased the percentage of α-helix/(β-sheet + random coil) and destroyed hydrogen bonding networks. Cell membrane potential and physiological status analysis showed that FA destroyed membrane integrity and increased the ratio of apoptotic and necrotic cells. These destroyed sludge EPSs structure and caused cell lysis, thus strongly inhibited the activities of hydrolytic microorganisms and sulfate reducing bacteria. Microbial analysis showed that FA reduced the abundance of functional microbes (e.g., Desulfobulbus and Desulfovibrio) and genes (e.g., MPST, CysP, and CysN) involved in organic sulfur hydrolysis and inorganic sulfate reduction. These findings unveil an actually existed but previously overlooked contributor to HS inhibition in WAS anaerobic fermentation.
游离氨（FA）是铵的非离子化形式，在剩余活性污泥（WAS）的厌氧发酵中大量存在。然而，其在WAS厌氧发酵过程中对硫转化，尤其是硫化氢（HS）产生的潜在作用此前未被认识到。这项工作旨在揭示FA如何影响WAS厌氧发酵中的厌氧硫转化。研究发现，FA显著抑制了HS的产生。随着FA浓度从0.04毫克/升增加到159毫克/升，HS产量降低了69.9%。FA首先攻击污泥胞外聚合物（EPSs）中的类酪氨酸蛋白和类芳香族蛋白，羰基首先受到影响，这降低了α-螺旋/（β-折叠+无规卷曲）的比例并破坏了氢键网络。细胞膜电位和生理状态分析表明，FA破坏了膜的完整性，增加了凋亡和坏死细胞的比例。这些破坏了污泥EPSs的结构并导致细胞裂解，从而强烈抑制了水解微生物和硫酸盐还原细菌的活性。微生物分析表明，FA降低了参与有机硫水解和无机硫酸盐还原的功能微生物（如脱硫球菌属和脱硫弧菌属）和基因（如MPST、CysP和CysN）的丰度。这些发现揭示了WAS厌氧发酵中一种实际存在但此前被忽视的抑制HS产生的因素。
