State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Nanjing University, Nanjing 210023, China; Department of Civil & Environmental Engineering, University of Washington, Box 352700, Seattle, WA 98195-2700, United States.
Department of Civil & Environmental Engineering, University of Washington, Box 352700, Seattle, WA 98195-2700, United States.
Water Res. 2017 Mar 15;111:154-162. doi: 10.1016/j.watres.2017.01.009. Epub 2017 Jan 3.
This study examined the significance of changes of UV absorbance and fluorescence of dissolved organic matter (DOM) as surrogate indicators for assessing the formation of bromate and biodegradable dissolved organic carbon (BDOC) during the ozonation of surface water and wastewater effluent. Spectroscopic monitoring was carried out using benchtop UV/Vis and fluorescence spectrophotometers and a newly developed miniature LED UV/fluorescence sensor capable of rapidly measuring UVA280 and protein-like and humic-like fluorescence. With the increase of O/DOC mass ratio, the plots of BDOC formation were characterized of initial lag, transition slope and final plateau. With the decrease of UV absorbance and fluorescence, BDOC concentrations initially increased slowly and then rose more noticeably. Inflection points in plots of BDOC versus changes of spectroscopic indicators were close to 35-45% loss of UVA254 or UVA280 and 75-85% loss of humic-like fluorescence. According to the data from size exclusion chromatography (SEC) with organic carbon detection and 2D synchronous correlation analyses, DOM fractions assigned to operationally defined large biopolymers (apparent molecular weight, AMW>20 kDa) and medium AMW humic substances (AMW 5.5-20 kDa) were transformed into medium-size building blocks (AMW 3-5.5 kDa) and other smaller AMW species (AMW<3 kDa) associated with BDOC at increasing O/DOC ratios. Appreciable bromate formation was observed only after the values of UVA254, UVA280 and humic-like fluorescence in O-treated samples were decreased by 45-55%, 50-60% and 86-92% relative to their respective initial levels. No significant differences in plots of bromate concentrations versus decreases of humic-like fluorescence were observed for surface water and wastewater effluent samples. This was in contrast with the plots of bromate concentration versus UVA254 and UVA280 which exhibited sensitivity to varying initial bromide concentrations in the investigated water matrixes. These results suggest that measurements of humic-like fluorescence can provide a useful supplement to UVA indices for characterization of ozonation processes.
本研究考察了紫外吸光度和溶解有机物（DOM）荧光变化作为评估地表水和废水臭氧氧化过程中亚硝酸盐和可生物降解溶解有机碳（BDOC）形成的替代指标的意义。采用台式紫外/可见和荧光分光光度计以及新开发的微型 LED 紫外/荧光传感器对光谱监测进行了研究，该传感器能够快速测量 UVA280 和蛋白质样和腐殖质样荧光。随着 O/DOC 质量比的增加，BDOC 形成的曲线特征为初始滞后、过渡斜率和最终平台。随着紫外吸光度和荧光的降低，BDOC 浓度最初缓慢增加，然后明显上升。BDOC 与光谱指标变化关系图中的拐点接近 UVA254 或 UVA280 损失 35-45%和腐殖质样荧光损失 75-85%。根据带有有机碳检测的尺寸排阻色谱（SEC）和二维同步相关分析的数据，分配给操作定义的大生物聚合物（表观分子量，AMW>20 kDa）和中等 AMW 腐殖质物质（AMW 5.5-20 kDa）的 DOM 级分转化为中等大小的构建块（AMW 3-5.5 kDa）和其他较小的 AMW 物质（AMW<3 kDa），与 O/DOC 比增加时的 BDOC 相关。只有当 O 处理样品中的 UVA254、UVA280 和腐殖质样荧光值相对于初始值分别降低 45-55%、50-60%和 86-92%时，才会观察到可观的亚硝酸盐形成。对于地表水和废水处理厂样品，溴酸盐浓度与腐殖质样荧光降低的关系图中没有观察到显著差异。这与溴酸盐浓度与 UVA254 和 UVA280 的关系图形成对比，后者显示了对所研究水基质中不同初始溴化物浓度的敏感性。这些结果表明，腐殖质样荧光的测量可以为臭氧氧化过程的表征提供有用的 UVA 指数补充。
