The pH of chlorination is an important factor affecting the formation of disinfection byproducts (DBPs). In this study, we discovered that the genotoxicity induced by chlorination can be effectively reduced under alkaline conditions. As the pH of chlorination increased from 6.5 to 8.5, the genotoxicity of investigated waters reduced by ∼30–90 %. By assessing the genotoxicity of the mixture of measured DBPs, it was found that the contribution of measured DBPs to the overall genotoxicity was lower than 5 %, and the significant reduction of genotoxicity was largely associated with unknown DBPs. The result of Pearson's correlation analysis indicated that humified organics and soluble microbial byproducts were likely responsible for the genotoxicity, and their derived genotoxic compounds (i.e., unknown DBPs) tended to decompose during alkaline chlorination. However, the control of genotoxicity by alkaline chlorination was achieved at the expense of promoting trihalomethane (THM) formation. The highest genotoxicity reduction (93 %) was observed for chlorinated granular activated carbon-treated waters, but the formation of THMs was promoted to a level approaching that in untreated waters. The inconsistent trend of overall genotoxicity and THM concentration during alkaline chlorination suggested the inadequacy of THMs as metric for DBP exposure, and considerations should also be given to the toxicity of bulk water in addition to regulated DBPs.

氯化的pH值是影响消毒副产物(DBP)形成的重要因素。在本研究中，我们发现在碱性条件下可以有效降低氯化引起的遗传毒性。随着氯化的 pH 值从 6.5 增加到 8.5，所研究的水体的遗传毒性降低了~30-90%。通过评估测得的DBPs混合物的遗传毒性，发现测得的DBPs对总体遗传毒性的贡献低于5%，遗传毒性的显着降低很大程度上与未知的DBPs有关。Pearson相关分析的结果表明，腐殖化有机物和可溶性微生物副产物可能是造成遗传毒性的原因，并且它们衍生的遗传毒性化合物（即未知的DBP）在碱性氯化过程中倾向于分解。然而，通过碱性氯化控制遗传毒性是以促进三卤甲烷（THM）形成为代价的。经氯化颗粒活性炭处理的水中观察到最高的遗传毒性降低（93%），但三卤甲烷的形成促进到接近未处理水中的水平。碱性氯化过程中总体遗传毒性和 THM 浓度的不一致趋势表明，THM 作为 DBP 暴露指标的不足，除了受管制的 DBP 外，还应考虑散装水的毒性。