溶解性有机物存在下多环芳烃衍生物产生及转化的微生物作用机制

Polycyclic aromatic hydrocarbons (PAHs) derivatives, the toxicities of which are higher than the corresponding PAHs, were frequently detected in wastewater receiving rivers in Beijing and Tianjin region, recently. The secondary effluent from wastewater treatment plants (WWTPs) is one of the major sources for these compounds to the wastewater receiving rivers. In this project, the formation and transformation of PAHs devivatives in a typical WWTP will be studied. The existance, distribution, patition of the target compounds in the WWTP will be investigated. The laborotary simulation experiment will be conducted. The partition of the target compounds in dissolved organic matter (DOM), the main component in domestic wastewater, and the combination with DOM will be defined. The characteristic microbial population related to the formation and transformation of target compounds will be identified. The synergistic effect mechanism of both DOM and characteristic microbial population to the formation and transformation of the target compounds will be ascertained. The formation and transformation approach of the PAHs derivatives in WWTP will be revealed. Based on all the above, an appropriate method of control and reduce this type of pollutants in the biological wastewater treatment process will be proposed. The result of this project will provide practical significance to control the risk of PAHs derivatives in the wastewater receiving rivers in Beijing and Tianjin region.

近年来，京津地区纳污河流中频繁检测出毒性强于母体多环芳烃（PAHs）的衍生物。污水处理厂二级出水是纳污河流中此类物质的主要来源之一。本项目围绕PAHs衍生物在污水处理厂中的生成与转化展开研究：以实地污水处理厂中目标物的存在、分布、分配状况分析并结合室内模拟实验为研究手段，明确目标物在生活污水的主要成分——溶解性有机物（DOM）——中的分配特性以及与DOM的结合机理；识别与目标物生成及转化相关的特征微生物种群；探明DOM与特征微生物对目标物产生与转化的协同作用机制，揭示污水处理厂中PAHs衍生物的产生与转化过程；在此基础上提出控制与削减污水生物处理工艺中此类污染物的方法与途径。本项目研究结果对京津地区纳污河流中PAHs衍生物等微量有机污染物风险控制具有实际意义。

本项目主要围绕母体多环芳烃（PAHs）及取代多环芳烃（SPAHs）在城市污水处理厂的去除与转化开展研究。首先建立了水体中5类SPAHs（多氯萘PCNs、氯代ClPAHs、甲基MPAHs、氧化OPAHs和硝基多环芳烃NPAHs）以及16种母体PAHs共计38种物质的同步检测方法，建立基质标准曲线抵消基质干扰，回收率多数可达70%-120%；方法检出限和定量限分别为0.01-27.6 ng/L和0.04-91.9 ng/L；具有较高的灵敏度和稳定性。应用此方法在污水厂及受纳河流中检出了6种PCNs+ClPAHs、4种MPAHs、4种OPAHs和16种PAHs；PCNs和ClPAHs浓度与MPAHs相近，低于OPAHs，三类SPAHs的总浓度与母体PAHs相近，因此在对PAHs进行风险评估时应全面考虑SPAHs类物质。SPAHs和PAHs在污水厂主要通过二级工艺中去除（45%-82%），吸附是二级工艺去除PAHs和SPAHs的主要过程，同时也有部分目标物通过生物降解作用去除；PAHs和SPAHs在三级工艺中去除率为0%-24%，主要通过臭氧氧化作用去除。污水厂三级工艺对PAHs+SPAHs排放通量的削减率比二级工艺仅减少9%和21%，因此，推测污水处理工艺升级改造并不会明显改善受纳水体中PAHs和SPAHs的污染。2010-2017年PAHs和MPAHs浓度逐渐降低，燃煤消耗量也逐渐下降，二者显著正相关，估算PAHs及MPAHs通过燃煤源头控制排放量削减率至少约为30%，表明源头控制是削减河流中PAHs和MPAHs的有效手段。模拟活性污泥工艺及光电催化处理过程中PAHs的转化，发现两种工艺中PAHs均可转化生成OPAHs；活性污泥工艺中目标物初始浓度不是影响去除率的主要因素，而添加的比污水中原有的目标物去除率更高（水相中分别为96%-100%和11%-100%，总相中分别为9%-41%和0%-28%），可能由于原有目标物与体系中溶解性有机物（DOM）接触时间较长，阻碍了目标物的吸附和降解；光电催化处理也证明了DOM的投加量并不会明显阻碍PAH的去除，而DOM与PAH结合时间减慢了PAH的去除速率。研究结果提出了燃煤源头控制是削减典型城市河流中PAHs和MPAHs的有效手段；DOM影响PAHs去除速率的研究结果为深入研究微量有机污染物在实际污水处理工艺中去除机制奠定了基础。