Reduction of haloacetonitrile-associated risk by adjustment of distribution system pH
Reduction of haloacetonitrile-associated risk by adjustment of distribution system pH
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通过调整分配系统 pH 值降低卤代乙腈相关风险
DOI：
10.1039/d3ew00230f
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发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Hanigan, David
中科院分区：
文献类型：
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作者：
Stewart, Kevin;An, Dong;Hanigan, David
由于卤代乙腈（HANs）和卤代乙酰胺（HAMs）与受调节的碳质消毒副产物（DBPs）相比的相对毒性，最近受到了广泛的关注。随着pH的增加，HAN水解成火腿和火腿水解成卤乙酸（HAAs）的速率增加，这些基团的毒性排序为HAN > HAM > HAA。因此，在饮用水分配过程中有意水解会减少接触汉斯和汉姆斯，从而降低毒理学风险。为了评估这种水解方案在减少输送水毒理学负担方面的潜力，我们研究了在常规处理的地表水和在不同pH下加入两种天然有机物分离物和游离氯的milliq水中HANs和HAMs的形成和降解。在5天的实验期结束时，pH为6、7.5和9的成品饮用水中的HAN浓度分别为12.5、7.1和1.9 μg L−1。相当于从测量的消毒副产物中计算的总毒性降低77% （pH值6至9）和45% （pH值7.5至9）。对天然有机物分离物的实验也得出了类似的结论。在来自全规模处理厂的样品和对分离物进行的实验中，当将HANs（一种不受管制但剧毒的DBPs）驱动到毒性较低的水解产物时，超过THM和HAA5监管限值的可能性增加了。我们发现，增加配电系统的pH值是降低han相关毒性的有效方法，但在实施前应仔细评估配电系统腐蚀、水垢稳定性以及违反THM和HAA法规的潜在权衡。
Haloacetonitriles (HANs) and haloacetamides (HAMs) have been scrutinized recently due to their relative toxicity compared to regulated carbonaceous disinfection byproducts (DBPs). Rates of HAN hydrolysis to HAMs and HAMs to haloacetic acids (HAAs) increase with pH and the ranked toxicity of these groups is HAN > HAM > HAA. Thus, intentional hydrolysis during distribution of drinking water would result in reduced exposure to HANs and HAMs, and subsequently lower toxicological risk. To evaluate the potential for such a hydrolysis scheme to reduce the toxicological burden of delivered water, we examined the formation and degradation of HANs and HAMs in conventionally treated surface water and in Milli-Q water spiked with two natural organic matter isolates and free chlorine at varying pH. HAN concentrations in finished drinking water at pH 6, 7.5, and 9 at the end of the 5-day experimental period were 12.5, 7.1, and 1.9 μg L−1, respectively, equivalent to a 77% (pH 6 to 9) and 45% (pH 7.5 to 9) decrease in summed calculated toxicity from the disinfection by-products measured. Similar conclusions followed from experiments with natural organic matter isolates. In samples from the full-scale treatment plant and experiments conducted with isolates, the potential to exceed THM and HAA5 regulatory limits was increased while driving HANs, an unregulated but highly toxic class of DBPs, to lower toxicity hydrolysis products. We find that increasing distribution system pH is an effective method to reduce HAN-associated toxicity, although potential tradeoffs in distribution system corrosion, scale stability, and the potential to violate THM and HAA regulations should be carefully evaluated prior to implementation.