School of Engineering, RMIT University, Melbourne, VIC, Australia.
School of Civil and Environmental Engineering, University of New South Wales, Sydney, NSW, Australia.
Sci Total Environ. 2020 Jun 15;721:137676. doi: 10.1016/j.scitotenv.2020.137676. Epub 2020 Mar 3.
The occurrence and fate of emerging contaminants (ECs) in surface water bodies is of increasing interest to water quality managers and environmental regulators throughout the world. Wastewater treatment plants are a major source of ECs in many aquatic environments. A modified Quantitative Water Air Sediment Interaction (QWASI) fugacity model was developed for a municipal wastewater lagoon system to study the behaviour of six representative ECs. As the wastewater lagoons were exposed to extensive periods of sunlight, the original model was modified by the addition of photolytic degradation as a removal mechanism. Laboratory studies were conducted over different seasons of a year to obtain the rate constants for the key processes of sunlight photodegradation, water and sediment transformation, as well as sediment sorption coefficients for the target ECs in the system to serve as model inputs. The model predicted the pathways for the different ECs and that at least 65% of the concentration of the ECs remained in the outflow of the first lagoon of the lagoon system after treatment. The greatest removal was predicted for sulfamethoxazole (35%) and the least for carbamazepine (5%). Multi-segment theory was applied to the single lagoon model and the predictions for the sequential six lagoon system were validated through field sampling. Sensitivity analysis revealed that the mass transfer coefficient between the water and sediment phases was the most influential parameter, with the four key process rate constants having various impacts depending on the EC. These results suggest that the modified QWASI model could be used to more accurately represent the fate and transport of ECs in this unique wastewater lagoon/stabilisation pond treatment system. Furthermore, it can be adapted to model a wide range of ECs in other wastewater treatment lagoon systems and thus assist with process optimisation and risk assessment of the treated water.
地表水体中新兴污染物（ECs）的出现和归宿越来越引起世界范围内水质管理者和环境监管者的关注。污水处理厂是许多水生环境中 ECs 的主要来源。为研究六种代表性 ECs 的行为，开发了一种改良的定量水-气-沉积物相互作用（QWASI）逸度模型，用于城市污水处理塘系统。由于污水处理塘暴露在大量阳光下，因此通过添加光降解作为去除机制对原始模型进行了修改。实验室研究在一年的不同季节进行，以获得系统中关键过程的速率常数，包括阳光光降解、水和沉积物转化，以及目标 ECs 的沉积物吸附系数，作为模型输入。该模型预测了不同 ECs 的途径，并且处理后至少有 65%的 ECs 浓度仍留在塘系统中第一个塘的流出物中。模型预测，磺胺甲恶唑（35%）的去除率最大，卡马西平（5%）的去除率最小。多段理论应用于单塘模型，通过现场采样验证了顺序六塘系统的预测。敏感性分析表明，水-沉积物相间的质量转移系数是最具影响力的参数，四个关键过程速率常数对 EC 的影响各不相同。这些结果表明，改良的 QWASI 模型可用于更准确地表示这种独特的污水处理塘/稳定塘处理系统中 ECs 的归宿和迁移。此外，它可以适应于模拟其他污水处理塘系统中广泛的 ECs，从而有助于处理水的过程优化和风险评估。
