污水处理厂与受纳水环境中典型家用杀生剂的降解转化机理研究

In recent years personal care products have received increasing attentions in general public and scientific community due to their high production volume and environmental contamination issue. Household biocides are a class of chemicals which are commonly used in daily household products and personal care products to inhibit or kill microbes. After use, these chemicals enter into the receiving aquatic environments via discharge of domestic wastewaters. Household biocides have been widely detected in the aquatic environment, but little is known about their fate in the environment. On the basis of our previous work, this project aims to investigate the concentration levels and removal efficiencies of some common biocides (disinfectants, azole fungicides and parabens preservatives) in municipal wastewater treatment plants in the Pearl River Delta Region, calculate the discharge of each biocide per capita based on the mass balance analysis, and assess the contamination characteristics and ecological risks of these biocides in the receiving aquatic environments. Through laboratory experiments, this project will study removal mechanisms of six representative biocides by activated sludge treatment process, and transformation by chlorination and UV disinfection including reaction kinetics, pathways and toxicity evaluation. This project will also study the photolysis of the six representative biocides in surface water by sunlight and biodegradation in water-sediment systems under different redox conditions in the laboratory. We will finally explore carbon isotope fractionation effects for the representative biocides during biological degradation and abiotic degradation. The results from this project research can assist evaluate the environmental fate of biocides and potential ecological risks.

近年有关高使用量个人护理品的环境污染问题引起了人们的关注。其中家用杀生剂是家庭日用品和个人护理品中常用的一类具抑菌或杀菌性能的化学品，使用后它们随污水排放到受纳水环境中。家用杀生剂广泛检出于受纳水环境中，但其环境归趋研究十分薄弱。在前期工作基础上，本项目选择珠三角城市生活污水处理厂及其受纳水环境研究常见三类杀生剂（消毒剂、唑类抗真菌剂和对羟基苯甲酸酯类防腐剂）在污水处理厂中的浓度水平、处理效率，基于质量平衡估算人均排放量，以及受纳水体中杀生剂的污染特征与生态风险；实验室模拟研究活性污泥法对6种典型杀生剂的去除机制、消毒处理工艺（氯、紫外）的降解转化动力学、降解途径与毒性变化规律；实验室模拟研究水环境中典型杀生剂的自然光解与微生物降解机理，利用单体同位素质谱分析研究生物降解过程与非生物降解（光解）过程对目标化合物碳同位素的分馏效应，为评价家用杀生剂的环境归趋与生态健康风险提供科学依据。

家用杀生剂是家庭日用品和个人护理品中常用的一类具抑菌或杀菌性能的化学品，使用后它们随污水排放到受纳水环境中，对水环境生物造成潜在影响。本项目选择珠三角城市生活污水处理厂及其受纳水环境研究常见三类杀生剂（消毒剂、唑类抗真菌剂和对羟基苯甲酸酯类防腐剂）在污水处理厂中的浓度水平、处理效率，估算人均排放量，以及受纳水体中杀生剂的污染特征与生态风险；实验室模拟研究污水处理厂消毒处理工艺（氯、紫外）对典型杀生剂的降解转化动力学、降解途径与毒性变化规律；实验室模拟研究水环境中典型杀生剂的微生物降解机理。通过以上研究，项目取得的主要成果有：（1）珠三角地区10个污水处理厂及其受纳河流中都广泛检出杀生剂：其中避蚊胺 （DEET）是污水厂水相中最主要的杀生剂，而活性污泥和脱水污泥中主要杀生剂为三氯卡班；污水处理工艺能有效去除杀生剂，十个污水处理厂对杀生剂平均去除率可高达75%，去除途径为微生物降解和活性污泥吸附；经估算，杀生剂的污染排放总量达289 t/y；东江流域地表水中主要检出尼泊金甲酯、甘宝素和DEET，沉积物中主要检出甘宝素、三氯生和三氯卡班，东江石龙断面∑17Biocides质量通量为3434 kg/y。（2）甘宝素在紫外光辐射（UV-225~425和 UV-254）下能迅速降解，其降解效率要显著高于氯氧化处理，活性氧（•OH、 1O2 和 O2-•），能促进了甘宝素的光降解，光降解途径主要为脱氯羟基化、脱氯、脱频哪酮等。紫外/氯氧化联合作用能有效加速甘宝素和氟康唑的降解。pH及共存组分影响降解速率，其中•OH是甘宝素和氟康唑紫外/氯氧化降解的主要活性自由基。（3）TCS和HHCB在水/沉积物体系中能够生物积累、生物转化和微生物降解。TCS和HHCB在沉积物7天达到吸附和积累平衡，其生物-沉积物积累因子（BSAFs）分别为2.07和2.50。霍夫迈斯特氏杆菌的存在显著加速了TCS和HHCB在体系中的消减，检测出TCS生物转化产物分别为甲基三氯生和三氯生O-硫酸盐。相关的研究成果已发表SCI论文14篇，第一标注9篇；培养博士研究生3名（其中2名已毕业）。