The proliferation and chlorine resistance of pathogenic bacteria in drinking water distribution systems (DWDSs) pose a serious threat to human health. In this study, the synergistic effects of ozonation pretreatment and trace phosphate on water quality health risk and microbial stability were investigated in the small-scale DWDSs simulated by biofilms annular reactors with cast iron coupons. The results indicated that ozonation of drinking water containing trace phosphate was equivalent to increasing microbial carbon and phosphorus sources, further leading to the rapid proliferation of opportunistic pathogens (OPs) in subsequent DWDSs. Under the influent condition of ozonation pretreatment and 0.6 mg/L phosphate, the gene copy numbers of living Legionella spp., Mycobacterium spp., and Acanthamoeba spp. reached up to 1.50 × 10⁴, 1.21 × 10⁴, and 2.29 × 10⁴ gene copies/mL, respectively. The extracellular polymeric substances from suspended biofilms in DWDSs exhibited higher content, molecular weight, and flocculating efficiency, contributing to the improvement of microbial chlorine resistance. Meanwhile, more Fe₃O₄ appeared in the corrosion products, which enhanced the extracellular electron transfer via cytochrome c and weakened the electrostatic repulsion between corrosion products and microbes in DWDSs. Finally, more active OP growth and microbial metabolic activity occurred in DWDSs. This study revealed that ozonation pretreatment and trace phosphate, as a green technology and an inconspicuous nutrient, respectively, can trigger significant microbial health risks in subsequent DWDSs. Therefore, the phosphate in drinking water should be more strictly restricted when ozonation technology is used in waterworks, especially without a biofiltration treatment process.

中文翻译：

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臭氧预处理和微量磷酸盐对模拟饮用水分配系统中水质、健康风险和微生物稳定性的协同效应


饮用水分配系统 （DWDS） 中病原菌的增殖和耐氯性对人类健康构成严重威胁。本研究在带有铸铁片的生物膜环形反应器模拟的小规模 DWDS 中研究了臭氧化预处理和微量磷酸盐对水质健康风险和微生物稳定性的协同效应。结果表明，含有痕量磷酸盐的饮用水臭氧化相当于增加微生物碳和磷源，进一步导致机会性病原体 （OPs） 在随后的 DWDS 中迅速增殖。在臭氧预处理和0.6 mg/L磷酸盐的进水条件下，活军团菌属、分枝杆菌属和棘阿米巴属的基因拷贝数分别达到1.50×10⁴、1.21×10⁴和2.29×10⁴个基因拷贝/mL。DWDS 中悬浮生物膜的细胞外聚合物物质表现出更高的含量、分子量和絮凝效率，有助于提高微生物对氯的抵抗力。同时，腐蚀产物中出现了更多的 Fe₃O₄，增强了通过细胞色素 c 的细胞外电子转移，减弱了 DWDSs 中腐蚀产物与微生物之间的静电排斥。最后，DWDS 中出现了更活跃的 OP 生长和微生物代谢活性。本研究揭示了臭氧化预处理和微量磷酸盐分别作为一种绿色技术和一种不显眼的营养物质，可以在后续的 DWDS 中引发重大的微生物健康风险。 因此，当自来水厂使用臭氧化技术时，尤其是没有生物过滤处理过程时，应更严格地限制饮用水中的磷酸盐。