Walpen Nicolas, Joss Adriano, von Gunten Urs
Swiss Federal Institute of Aquatic Science and Technology (Eawag), 8600 Dübendorf, Switzerland.
Swiss Federal Institute of Aquatic Science and Technology (Eawag), 8600 Dübendorf, Switzerland; Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, 8092 Zurich, Switzerland; School of Architecture, Civil and Environmental Engineering (ENAC), École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland.
Water Res. 2022 Feb 1;209:117858. doi: 10.1016/j.watres.2021.117858. Epub 2021 Nov 12.
Ozonation of secondary-treated wastewater for the abatement of micropollutants requires a reliable control of ozone doses. Changes in the UV absorbance of dissolved organic matter (DOM) during ozonation allow to estimate micropollutant abatement on-line and were therefore identified as feed-back control parameter. In this study, the suitability of the electron-donating capacity (EDC) as an additional surrogate parameter which is independent of optical DOM properties was evaluated during full-scale ozonation. For this purpose, a recently developed EDC analyzer was enhanced to enable continuous on-line EDC and UV absorbance measurements. During a multi-week monitoring campaign at the wastewater treatment plant of Zurich, Switzerland, specific ozone doses were varied from 0.13 to 0.91 mg⋅mg and selected micropollutants with different ozone reactivities were analyzed by LC-MS in conjunction with bromate analysis by IC-MS. In agreement with previous laboratory studies, the relative residual UV absorbance and EDC both decreased exponentially as a function of the specific ozone dose and, in comparison to the residual UV absorbance, residual EDC values showed a more pronounced decrease at low specific ozone doses ≤0.34 mg⋅mg. Logistic regression models allowed to estimate relative residual micropollutant concentrations in the ozonation effluent using either the residual UV absorbance or EDC as explanatory variable. Averaging those models along the explanatory variables allowed to estimate target values in relative residual UV absorbances and EDC for specific micropollutant abatement targets. In addition, both parameters allowed to identify conditions with elevated conversions of bromide to bromate. Taken together, these findings show that the integration of relative residual EDC values as a second control parameter can improve existing absorbance-based ozonation control systems to meet micropollutant abatement targets, particularly for treatment systems where low ozone doses are applied.
对二级处理后的废水进行臭氧化以去除微污染物需要可靠地控制臭氧剂量。臭氧化过程中溶解有机物（DOM）的紫外吸光度变化可用于在线估算微污染物的去除情况，因此被确定为反馈控制参数。在本研究中，在全规模臭氧化过程中评估了作为与光学DOM特性无关的附加替代参数的电子供体能力（EDC）的适用性。为此，对最近开发的EDC分析仪进行了改进，以实现连续在线EDC和紫外吸光度测量。在瑞士苏黎世的污水处理厂进行的为期数周的监测活动中，特定臭氧剂量在0.13至0.91 mg·mg之间变化，并通过液相色谱-质谱联用离子色谱-质谱法分析溴酸盐，对具有不同臭氧反应性的选定微污染物进行了分析。与之前的实验室研究一致，相对残余紫外吸光度和EDC均随特定臭氧剂量呈指数下降，并且与残余紫外吸光度相比，在特定臭氧剂量≤0.34 mg·mg时，残余EDC值下降更为明显。逻辑回归模型允许使用残余紫外吸光度或EDC作为解释变量来估算臭氧化流出物中相对残余微污染物浓度。对这些模型沿解释变量进行平均，可以估算出针对特定微污染物去除目标的相对残余紫外吸光度和EDC的目标值。此外，这两个参数都可以识别溴化物向溴酸盐转化率升高的条件。综上所述，这些发现表明，将相对残余EDC值作为第二个控制参数进行整合，可以改进现有的基于吸光度的臭氧化控制系统，以实现微污染物去除目标，特别是对于应用低臭氧剂量的处理系统。
