Ultrafiltration is widely used to treat various environmental waters, and on-line membrane cleaning with various chemical reagents is frequently employed to sustain the filtration flux. However, the residue of cleaning agents in the ultrafiltration system is unavoidable, which may affect microbiological properties and biofilm formation during the next-round filtration. By investigating the changes in microbial characteristics, and their biofouling behaviors after exposure to HCl, NaOH, NaClO, citric acid (CA), and sodium dodecyl sulfonate (SDS), this study fills a knowledge gap in microbial responses to various types of chemical cleaning agents in an ultrafiltration system. The result shows that HCl, NaOH, and NaClO affect the bacterial properties and subsequent attachment on the membrane surface, while CA and SDS have no obvious influence on microorganisms. Specifically, HCl, NaOH, and NaClO reduce the hydrophobicity and mean size of suspended microorganisms, increase the extracellular polymeric substances (EPS) release, and trigger intracellular reactive oxygen species (ROS) generation, resulting in the death of a large quantity of microorganisms. Due to the self-protecting strategy, plenty of living cells aggregate on the membrane surface and form a cake layer with a stratified structure, causing more severe membrane biofouling.

中文翻译：

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超滤膜在线清洗过程中微生物对各种化学试剂的反应

超滤被广泛用于处理各种环境水，并且经常使用各种化学试剂在线清洗膜来维持过滤通量。然而，超滤系统中清洗剂的残留是不可避免的，这可能会影响下一轮过滤过程中的微生物特性和生物膜的形成。本研究通过调查微生物特征的变化及其在接触 HCl、NaOH、NaClO、柠檬酸 (CA) 和十二烷基磺酸钠 (SDS) 后的生物污染行为，填补了微生物对各种化学清洗反应的知识空白超滤系统中的试剂。结果表明 HCl、NaOH 和 NaClO 影响细菌性质和随后在膜表面的附着，而CA和SDS对微生物没有明显影响。具体而言，HCl、NaOH和NaClO降低了悬浮微生物的疏水性和平均大小，增加了细胞外聚合物（EPS）的释放，并引发了细胞内活性氧（ROS）的产生，导致大量微生物死亡。由于自我保护策略，大量活细胞聚集在膜表面，形成具有分层结构的饼层，造成更严重的膜生物污染。