再生水渗滤过程中磺胺类抗生素对土壤微生物活性及DBPs前驱物去除的影响机制与调控

Sulfonamides antibiotics in secondary effluent would significant restrict the operational efficiency of infiltration systems, for their high ecotoxicity and significant accumulation rate in soil. However, the inhibition mechanism of those sulfonamides on the biomass activities and subsequent negative effect on the removal of disinfection by-products precursors during the infiltration systems operation was still unclear. To clarify the characteristics of the accumulation, bioavailability and biodegradation pathways of typical sulfonamides (sulfamethoxazole, sulfadiazine, sulfapyridine, sulfamethazine, sulfamethazine) during secondary effluent reclaiming, lab-scale soil column/sequential column recharging systems will be constructed and the operational performance are analyzed based on electrochemical analysis, spectrum analyzing, as well as batch adsorption tests. Secondly, negative effects of those accumulated sulfonamides on the distribution/activity of microbial groups (related to C-, N-nutrients biodegradation) would be evaluated via high-throughput sequencing, and the corresponding toxicological threshold values of those sulfonamides be emphatically analyzed. Subsequently, variation of C-, N-DBPs (disinfection by products) formation potential under the C-, N-nutrients removal inhibition are deeply evaluated. Finally, ecotoxicological characterization of the formed DBPs, sulfonamides, and their intermediates within the obtained reclaimed water will be evaluated. Combined with the analyzing of the rate limiting factors for DBPs precursors removal, as well as the chem/biotoxicity assessment, control measures of sulfonamides and DBPs induced ecotoxicity of the reclaimed water from recharging system are summarized. The investigation will provide theoretical basis as well as technical support for the steady-state operation of secondary effluent recharging system, which could deal with the negative effect of typical antibiotics.

磺胺类抗生素生物毒性显著且在土壤中易累积，污水厂二级出水渗滤过程中此类物质广泛存在影响着渗滤系统的高效运行。针对渗滤系统长期运行中磺胺类抗生素如何抑制功能微生物活性，并影响消毒副产物(DBPs)前驱物去除这一尚待探索的科学议题，本项目以磺胺甲恶唑、磺胺吡啶、磺胺嘧啶、磺胺甲嘧啶、磺胺二甲嘧啶为研究对象，首先通过人工/序批式渗滤实验，辅以电化学、色谱/光谱技术，深入分析其在渗滤系统累积机理、生物有效性特征及降解途径；基于渗滤系统微生物群落分布和抑菌活性实验，借助DNA高通量测序，阐明抗生素对渗滤系统中碳/氮营养物质代谢相关功能微生物的毒性阈值和致毒机理；在此基础上揭示抗生素抑营养物质代谢下碳系、氮系DBPs生成特征；通过入渗DBPs前驱物去除限制性因子分析和出水生物毒性实验，提出渗滤所得再生水风险调控措施。研究成果可为渗滤所得再生水中抗生素/中间产物、DBPs有效控制提供理论依据和技术支撑。

抗生素生物毒性显著且在土壤中易累积，污水厂二级出水渗滤过程中抗生素的广泛存在影响着渗滤系统的高效运行。本项目以磺胺类、阿莫西林、四环素、左氧氟沙星等典型抗生素为研究对象，首先通过人工/序批式渗滤实验，分析了上述典型抗生素在渗滤系统累积/去除特征机理、中间产物分布及代谢途径；结果表明，表层土壤（0-25 cm）对阿莫西林和四环素的削减起着关键作用，四环素则在25 cm深度以上去除效果良好，但其土壤中的累积量比阿莫西林低。抗生素降解过程中，磺胺甲恶唑在模拟土壤渗滤系统中主要是N-S键断裂以及异恶环的变化，阿莫西林为β内酰胺环解环，四环素主要是异构后的脱甲基、脱羧基，左氧氟沙星为羟基取代氟和哌嗪环断裂。基于渗滤系统微生物群落分布和抑菌活性实验，阐明累积抗生素对渗滤系统功能微生物毒性效应、阈值及致毒机理；结果表明，三种抗生素对COD、BOD、DOC去除均有所抑制。从Biolog-ECO微平板的分析可知，抗生素的施加一定程度上抑制了土壤微生物代谢活性；且高浓度磺胺嘧啶对土壤氨氧化过程产生了负面影响。AWCD最大值及变化趋势上均呈现空白>阿莫西林>左氧氟沙星>四环素。揭示了抗生素抑功能微生物活性后渗滤系统中 DBPs前驱物去除特征及机制；在甲氧苄啶反应过程中，反应时间，消毒剂投加量和溶液pH均对N-DBPs 的生成有一定影响。磺胺类抗生素氯化氧化主要归功于苯胺基断裂，苯胺的亲电取代，嘧啶基的断裂。通过入渗DBPs前驱物去除限制性因子分析和出水生物毒性实验，进行含抗生素污水厂出水的土壤渗滤所得再生水风险评价。阿莫西林出水生态风险为低风险（0.007），四环素由高风险（5.988）变为临近中风险（1.43）；左氧氟沙星由高风险（1.351）变为中风险（0.51）。将渗滤出水与再生水回用标准相比，发现所有柱子75 cm后的出水即已满足景观回用与杂用水对常规污染物的限值。所有柱子100 cm后的常规污染物浓度除了氨氮外，均已满足井灌要求。研究成果可为渗滤所得再生水中抗生素/中间产物、DBPs有效控制提供理论依据和技术支撑。