城市污水处理厂内分泌干扰物的全态检测、迁移转化及排放风险研究

Endocrine disrupting chemicals (EDCs) are a class of emerging pollutants with considerably high toxicity even at trace levels, so have attained much attention of researchers in recent years. One major pollution source of EDCs is the municipal sewage treatment plants (STP), which are in turn a key node for controlling the discharge of EDCs into our environment. This project, by selecting two typical groups of EDCs (i.e., estrogens and phenols), aims to investigate their distribution pattern, transport and transformation law, degradation mechanisms, and emission risks in several STPs adopting representative biological treatment processes. First of all, based on chromatography-mass spectrometry technologies, highly selective and sensitive analytical methods for comprehensively detecting target EDCs (including free and conjugated forms) in both liquid and solid phases will be developed. Thereafter, the distribution, transport and transformation of target EDCs in three most commonly used treatment process (A/O, A/A/O, Oxidation ditch) will be clarified. The major degradation process and mechanisms will be determined through EDCs mass balance and byproducts identification. The main species and forms of target EDCs present in the effluent and excess sludge will be analyzed. Finally, the potential environmental risk of target EDCs discharged from municipal sewage treatment plants will be assessed by analyzing their estrogenic disrupting activity. The findings of this project are expected to clarify the distribution, transport and transformation, fate and potential risk of EDCs, and thus providing theoretical support to optimize sewage treatment processes.

内分泌干扰物（EDCs）是一类在环境中赋存浓度虽低但毒性较大的特殊污染物，近年来受到国内外学者的广泛关注。城市污水处理厂是环境中EDCs污染的主要来源之一，也是控制EDCs向环境中排放的重要环节。本项目拟以雌激素和酚类这两类典型EDCs为对象，通过对其自由态和结合态的全面考察，研究其在污水处理厂中的分布特征、迁移转化规律、降解机理及排放风险。首先，基于色谱-质谱技术，开发可同步检测污水及污泥两相中EDCs自由态及结合态的检测方法；通过调查采样，掌握EDCs在三种典型污水处理工艺（A/O、A/A/O、氧化沟）中的分布特征与迁移转化规律，明确其重点去除工段及降解机理，解析外排出水与剩余污泥中EDCs的种类及形态；通过对相关样品的雌激素干扰效应检测，评价城市污水处理厂EDCs的潜在环境风险。本项目的研究结果将揭示城市污水处理厂中EDCs的分布、迁移转化、归趋及风险，为处理工艺的优化运行提供依据。

本课题以雌激素和酚类两类典型内分泌干扰物（EDCs）为研究对象，对其自由态和结合态在城市污水处理厂中的分布特征、迁移转化规律及排放风险展开了系统研究。首先，克服了污水及污泥的复杂基质干扰，建立了多类EDCs的高效同步分析检测方法，在此基础上，以全国范围内多家污水厂大规模采样与两家典型污水厂长期采样相结合，研究了EDCs在污水厂分布的一般规律、归趋特征、重点去除工段及影响因素；其次，解析了自由态及结合态EDCs在污水处理工艺中的迁移转化规律及去除机理；最后，对污水厂出水及污泥中EDCs的排放风险水平进行评估，甄别了重点风险物质。.结果显示：1）通过对14家污水处理厂的调查，发现EDCs进水浓度受季节和地域差异影响较小，而受进水组成影响显著。在人口密度高的地区，进水中自由态雌激素（Free estrogens，FEs）与结合态雌激素（Conjugated estrogens，CEs）浓度较高，而工业废水比例升高则会导致酚类EDCs（Phenolic EDCs，PEs）浓度上升；生物处理工艺是EDCs浓度削减的关键环节，影响CEs、FEs与PEs去除的主要因素分别为温度、HRT与SRT，根据各类EDCs的沿程转化和归趋，推断其主要去除方式分别为酶促水解、共代谢降解与污泥吸附；Cl2、O3等后续氧化工艺可进一步提升对EDCs的去除效率；2）CEs的降解途径必须经过酶促水解这一关键步骤，其中硫酸盐结合态的水解过程较慢，导致CEs在总雌激素摩尔浓度中的占比在生物处理段持续上升，进而在总出水中的比例达到13.5–100%，说明其更易穿透处理流程；FEs的去除与硝化反硝化过程中的共代谢作用密切相关；PEs在水相去除较快，但可通过生物降解与污泥吸附之间的平衡在泥相上大量赋存；3）以雌二醇当量活性（Estradiol equivalence, EEQ）及风险商（Risk quotient, RQ）综合评估了EDCs的排放风险，出水、剩余污泥中EEQ浓度分别为0.6–9.4 ng L–1和20.6–37.4 ng g–1，出水中的高风险物质依次为E1、E2、E1-3S、E2-3S和EE2，剩余污泥中的高风险物质依次为E1、E2-3S、NP、E2。以上研究结果明晰了多类EDCs在城市污水厂中的主要去除途径和影响因素，为我国城市污水厂中EDCs污染的综合管控提供了科学依据。