State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Nanjing University, Nanjing, 210023, China.
Key Laboratory of Surficial Geochemistry Ministry of Education, School of Earth Sciences and Engineering, Hydrosciences Department, Nanjing University, Nanjing, 210023, China.
Water Res. 2018 Nov 15;145:354-364. doi: 10.1016/j.watres.2018.08.030. Epub 2018 Aug 13.
Ozone is an effective oxidant and disinfectant commonly used for elimination of micropollutants and inactivation of resistant microbes. However, undesirable oxidation/disinfection byproducts such as bromate might form during ozonation. In this study, the UV absorbance and fluorescence indices were applied as surrogate indicators for predicting the inactivation of bacteria and formation of bromate during ozonation of water and wastewater effluents. The inactivation efficiencies of lab-cultured Escherichia coli (E. coli) and autochthonous bacteria were measured by plating (for E. coli only) and flow cytometry with fluorescence staining. During ozonation of E. coli spiked into wastewater effluents (∼10 cell/mL), the priority of inactivation efficiency determined by different cell viability methods were in the order of CFU > membrane damage > DNA damage. Approximately, 99% membrane damage and/or 90% DNA damage are conservatively supposed as an indicator for sufficient bacterial inactivation as well as degradation of antibiotic resistance genes. The related required O dosing thresholds for sufficient inactivation of E. coli and autochthonous bacteria refer to ∼0.6 O/DOC (g/g), ∼50% decrease of UVA254, ∼60% decrease of UVA280, or ∼80% decrease of humic-like fluorescence. Within the range of 10-10 cell/mL, the bacterial concentration did not have significant effects on the required thresholds of the specific O doses or spectroscopic indicators required for bacterial inactivation. The addition of 50 mM tert-BuOH as ·OH scavenger increased the required specific ozone doses but decreased the losses of spectroscopic indicators necessary for sufficient bacterial inactivation, and also suggested that the membrane/DNA damages for bacterial inactivation were mainly attributed to the direct O attacks. The bromate concentration was determined using ion chromatography with MS/MS detection. The results showed that when O was dosed at the required thresholds for sufficient bacterial inactivation, bromate formation could usually be suppressed below 10 μg/L. The present work supports that it is possible to reach a balance between bacterial inactivation and bromate formation.
臭氧是一种有效的氧化剂和消毒剂，常用于去除微污染物和灭活抗性微生物。然而，在臭氧氧化过程中可能会形成溴酸盐等不理想的氧化/消毒副产物。在这项研究中，紫外线吸收和荧光指数被用作预测水和废水处理中细菌失活和溴酸盐形成的替代指标。通过平板计数法（仅用于大肠杆菌）和荧光染色流式细胞术测量实验室培养的大肠杆菌（E. coli）和土著细菌的灭活效率。在向废水处理中添加（约 10 个细胞/mL）的大肠杆菌的臭氧氧化过程中，不同细胞活力测定方法确定的灭活效率优先级顺序为 CFU > 膜损伤 > DNA 损伤。大约 99%的膜损伤和/或 90%的 DNA 损伤被保守地认为是足够的细菌灭活以及抗生素抗性基因降解的指标。足够灭活大肠杆菌和土著细菌所需的相关 O 剂量阈值分别约为 0.6 O/DOC（g/g）、UVA254 降低 50%、UVA280 降低 60%或腐殖质样荧光降低 80%。在 10-10 个细胞/mL 的范围内，细菌浓度对特定 O 剂量或用于细菌灭活的光谱学指标所需的阈值没有显著影响。添加 50 mM 叔丁醇作为·OH 清除剂会增加所需的特定臭氧剂量，但会减少充分灭活细菌所需的光谱指标的损失，并表明细菌失活的膜/DNA 损伤主要归因于直接 O 攻击。溴酸盐浓度使用离子色谱法（带 MS/MS 检测）确定。结果表明，当 O 剂量达到足够细菌灭活的所需阈值时，溴酸盐的形成通常可以抑制在 10 μg/L 以下。本工作表明，在细菌灭活和溴酸盐形成之间达到平衡是可能的。
