Evaluation of optical surrogates for the characterization of DOM removal by coagulation
Evaluation of optical surrogates for the characterization of DOM removal by coagulation
复制标题
用于表征混凝去除 DOM 的光学替代物的评估
DOI：
10.1039/c5ew00024f
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发表时间：
2015
影响因子：
4.5
通讯作者：
R. Summers
中科院分区：
文献类型：
--
作者：
J. Korak;F. Rosario‐Ortiz;R. Summers
光学替代品（即吸光度和荧光）由于其作为在线传感器的潜力而在监测饮用水处理过程中受到关注。本研究比较了使用不同的光学替代物来模拟在 22 种不同水质（特定紫外线吸光度 (SUVA254) – 1.0 至 4.0 L mgC−1 m−1）的源水中，使用剂量范围为 5 至 120 mg L−1 的硫酸铝混凝去除溶解有机碳 (DOC)。开发了线性回归，将激发-发射矩阵（2029 个波长对）中离散波长对的 DOC 去除百分比与荧光减少百分比联系起来。在大于 375 nm 的所有发射波长下，DOC 去除率的平均 95% 预测区间在 10.5-15% 之间，这表明荧光监测中使用的波长选择相对不重要。没有内部滤光片校正的荧光数据导致模型性能下降，但在发射波长大于 400 nm 时，预测区间仍然在 12-15% 之间。相比之下，在 254 nm 处具有 UV 吸光度的类似模型的平均预测区间为 10.5%（DOCr% = 0.7 UVr%，R2 = 0.91），与最佳荧光波长组合的表现相同。额外的建模发现，由于相关的自变量，串联跟踪多个光学替代物并不能提高模型性能。原水光学特性（SUVA254 和荧光比）模拟了单剂量混凝剂（~40 mg L−1）下 DOC 的去除情况，但荧光指标并未显着优于 SUVA254。由 112 个荧光样本和 6 个经过验证的组件构建的 PARAFAC 模型展示了数据集中的荧光行为范围，并指导荧光比率的选择，以根据原水特征预测去除情况。这些结果表明，荧光波长对于测量原始样品和澄清样品的在线监测方法相对不重要，但发射波长是仅根据原水特性预测去除的驱动因素。
Optical surrogates (i.e., absorbance and fluorescence) are of interest to monitor drinking water treatment processes due to their potential for implementation as online sensors. This study compares the use of different optical surrogates to model dissolved organic carbon (DOC) removal by coagulation with aluminum sulfate in the dose range of 5 to 120 mg L−1 in 22 source waters with a wide range of water qualities (specific UV absorbance (SUVA254) – 1.0 to 4.0 L mgC−1 m−1). Linear regressions were developed relating percent DOC removal to percent fluorescence decrease at discrete wavelength pairs in an excitation-emission matrix (2029 wavelength pairings). DOC removal was modeled with an average 95% prediction interval between 10.5–15% at all emission wavelengths greater than 375 nm, suggesting that wavelength selection for use in fluorescence monitoring is relatively unimportant. Fluorescence data without inner filter corrections led to a decrease in model performance, but prediction intervals were still between 12–15% at emission wavelengths greater than 400 nm. By comparison, the average prediction interval for an analogous model with UV absorbance at 254 nm was 10.5% (DOCr% = 0.7 UVr%, R2 = 0.91), performing the same as the best possible fluorescence wavelength combinations. Additional modeling found that tracking multiple optical surrogates in tandem does not improve model performance due to correlated independent variables. Raw water optical properties (SUVA254 and fluorescence ratios) modeled DOC removal at a single coagulant dose (~40 mg L−1), but fluorescence indicators did not significantly outperform SUVA254. A PARAFAC model built with 112 fluorescence samples with six validated components demonstrated the range of fluorescence behaviors in the dataset and guided the selection of fluorescence ratios to predict removal based on raw water characteristics. These results demonstrated that fluorescence wavelength is relatively unimportant for online monitoring approaches that measure both raw and clarified samples, but emission wavelength is a driving factor for predicting removal based solely on raw water characteristics.