Role of effluent organic matter in the photochemical degradation of compounds of wastewater origin
Role of effluent organic matter in the photochemical degradation of compounds of wastewater origin
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DOI：
10.1016/j.watres.2016.12.016
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发表时间：
2017-03-01
期刊：
影响因子：
12.8
通讯作者：
MacKay, Allison A.
中科院分区：
文献类型：
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作者：
Bodhipaksha, Laleen C.;Sharpless, Charles M.;MacKay, Allison A.
处理后的废水流出物的光反应性不同于天然有机物，废水中微污染物的间接光转化率预计取决于废水对总流的贡献率。测量了四种常见废水来源化合物（磺胺甲恶唑、磺胺二甲氧嘧啶、西咪替丁和咖啡因）在河水、处理过的城市污水流出物和两者的混合物中的光降解率，以模拟环境系统中可能发生的各种废水-水流混合条件。选择化合物是因为它们具有独特的光降解途径，光化学产生的反应中间体，三态激发态有机物（(OM)-O-3*），单线态氧（O-1(2)）和羟基自由基（OH中心点）。对于所有化合物，在废水中观察到的光降解率高于上游河水。磺胺甲恶唑的降解主要是通过直接光解进行的，在含废水的样品中，OH中心点和碳酸盐自由基以及其他未识别的反应中间体也可能有一定的作用。磺胺二甲氧嘧啶也主要通过直接光解降解，天然有机物对这一过程的抑制程度似乎比光屏蔽预测的要大。在出水有机物存在的情况下，磺胺二甲氧嘧啶与OH中心点和O-1(2)发生附加反应。在所有水样中，西咪替丁通过与O-1(2)（>95%）反应降解，咖啡因通过与OH '（>95%）反应降解。在河水混合物中，所有化合物的光降解速率常数随出水馏分的增加而增加。保守混合模型能够预测羟基自由基反应的反应速率常数，但对(OM)-O-3*和O-1(2)途径的反应速率常数估计过高。最后，化合物降解率常数归一化为与E-2/E-3比值相关的水的光吸收率（样品在254 nm处的吸光度除以样品在365 nm处的吸光度），这表明有机物的光学性质可能有望预测不同流出物混合比下的间接化合物光降解率。(C) 2016 Elsevier Ltd.版权所有。
The photoreactivity of treated wastewater effluent organic matter differs from that of natural organic matter, and the indirect phototransformation rates of micropollutants originating in wastewater are expected to depend on the fractional contribution of wastewater to total stream flow. Photodegradation rates of four common compounds of wastewater origin (sulfamethoxazole, sulfadimethoxine, cimetidine and caffeine) were measured in river water, treated municipal wastewater effluent and mixtures of both to simulate various effluent-stream water mixing conditions that could occur in environmental systems. Compounds were chosen for their unique photodegradation pathways with the photochemically produced reactive intermediates, triplet-state excited organic matter ((OM)-O-3*), singlet oxygen (O-1(2)), and hydroxyl radicals (OH center dot). For all compounds, higher rates of photodegradation were observed in effluent relative to upstream river water. Sulfamethoxazole degraded primarily via direct photolysis, with some contribution from OH center dot and possibly from carbonate radicals and other unidentified reactive intermediates in effluent-containing samples. Sulfadimethoxine also degraded mainly by direct photolysis, and natural organic matter appeared to inhibit this process to a greater extent than predicted by light screening. In the presence of effluent organic matter, sulfadimethoxine showed additional reactions with OH center dot and O-1(2). In all water samples, cimetidine degraded by reaction with O-1(2) (>95%) and caffeine by reaction with OH" (>95%). In river water mixtures, photodegradation rate constants for all compounds increased with increasing fractions of effluent. A conservative mixing model was able to predict reaction rate constants in the case of hydroxyl radical reactions, but it overestimated rate constants in the case of (OM)-O-3* and O-1(2) pathways. Finally, compound degradation rate constants normalized to the rate of light absorption by water correlated with E-2/E-3 ratios (sample absorbance at 254 nm divided by sample absorbance at 365 nm), suggesting that organic matter optical properties may hold promise to predict indirect compound photodegradation rates for various effluent mixing ratios. (C) 2016 Elsevier Ltd. All rights reserved.