College of Eco-Environmental Engineering, Guizhou Minzu University, Guiyang, Guizhou Province 550025, PR China; Department of Chemical Engineering, University of Toledo, 3048 Nitschke Hall, 2801 W. Bancroft St., Toledo, OH 43606-3390, USA.
Department of Civil and Environmental Engineering, University of Toledo, 3006 Nitschke Hall, 2801 W. Bancroft St., Toledo, OH 43606-3390, USA.
Sci Total Environ. 2021 Jan 20;753:141606. doi: 10.1016/j.scitotenv.2020.141606. Epub 2020 Aug 10.
This study investigated the role of biofilms on the formation and decay of disinfection by-products (DBPs) in chlorine (Cl) or monochloramine (NHCl) disinfected reactors under the conditions related to drinking water distribution systems (DWDSs). Biofilm analysis results revealed that at 0.5 mg/L of disinfectant residual, both Cl and NHCl were not effective to remove biofilms. As the disinfectant residual increased, biofilms could be eradicated by Cl, while remaining biofilms were still present even under the highest allowable NHCl dose (4 mg/L) for 25 days. Low DBP formation was observed under the recommended minimum Cl residual (0.5 mg/L), which could be attributed to limited Cl reactions with biofilms, as well as a combination of the volatilization and biodegradation of DBPs. However, when Cl residuals reached 2 mg/L, DBP concentrations in bulk water increased sharply beyond the DBP formation of the feed solution, with trihalomethanes and haloacetic acids being the most prevalent DBP species. The sharp increase was temporary for 15 days because of the removal of biofilms. For unregulated DBPs, high levels of haloacetonitriles were observed as attached biofilms reacted with the increased Cl dose and provided an additional organic nitrogen source for nitrogenous DBP formation. When maximum Cl residual (4 mg/L) was applied, no further increase of DBPs was observed because of biofilm eradication. For NHCl disinfection, the DBP levels were much lower than those of Cl disinfection, with small differences in DBP formation for different NHCl residuals. Overall, this study provides insights into optimizing disinfection protocols for water utilities by balancing the benefits of disinfection application for biofilm control with minimized toxic DBP formation in DWDSs.
本研究考察了生物膜在与饮用水分配系统（DWDS）相关条件下，在氯（Cl）或一氯胺（NHCl）消毒反应器中形成和衰减消毒副产物（DBP）中的作用。生物膜分析结果表明，在 0.5mg/L 的消毒剂残留量下，Cl 和 NHCl 均无法有效去除生物膜。随着消毒剂残留量的增加，Cl 可以消灭生物膜，而即使在 25 天内允许的最高 NHCl 剂量（4mg/L）下，仍存在残留生物膜。在推荐的最小 Cl 残留量（0.5mg/L）下，观察到低 DBP 形成，这可能归因于有限的 Cl 与生物膜的反应，以及 DBP 的挥发和生物降解的结合。然而，当 Cl 残留量达到 2mg/L 时，由于生物膜的去除，水中的 DBP 浓度在批量水中急剧增加，超过了进料溶液中 DBP 的形成量，其中三卤甲烷和卤乙酸是最常见的 DBP 种类。由于生物膜的去除，这种急剧增加是暂时的，持续了 15 天。对于未受管制的 DBP，由于附着生物膜与增加的 Cl 剂量反应，提供了额外的有机氮源用于含氮 DBP 的形成，观察到高浓度的卤乙腈。当最大 Cl 残留量（4mg/L）施加时，由于生物膜的消除，DBP 没有进一步增加。对于 NHCl 消毒，DBP 水平远低于 Cl 消毒，不同 NHCl 残留量的 DBP 形成差异较小。总的来说，本研究通过平衡消毒应用对生物膜控制的益处与 DWDS 中最小化毒性 DBP 形成，为水公用事业优化消毒方案提供了见解。
