Oak Ridge Institute for Science and Education (ORISE) Post-Doctoral Fellow at U.S. Environmental Protection Agency , Cincinnati , Ohio 45268 , United States.
National Risk Management Research Laboratory , U.S. Environmental Protection Agency , Cincinnati , Ohio 45268 , United States.
Environ Sci Technol. 2019 Aug 20;53(16):9352-9360. doi: 10.1021/acs.est.9b01189. Epub 2019 Aug 2.
Sediment accumulation in water storage tanks may protect microorganisms from disinfectant exposure, causing the degradation of water quality. However, microbial activity and disinfectant penetration within water storage sediment remain largely uncharacterized. This study evaluated the penetration of monochloramine and free chlorine into a 2 cm (20000 μm) deep drinking water storage tank sediment using microelectrodes. The sediment was successively exposed to monochloramine for 4 months, free chlorine for 2 months, and monochloramine for 2 months. Temporal monochloramine, free chlorine, dissolved oxygen (DO), pH, ammonium, nitrite, and nitrate profiles were acquired using microelectrodes. The results showed that complete monochloramine or free chlorine penetration was not observed. Likewise, DO never fully penetrated the sediment, progressing inward with time to a maximum depth of 10000 μm and indicating microbial activity persisted over the entire 8 months. Decreasing ammonium and increasing nitrate concentrations, with minimal nitrite accumulation, further demonstrated microbial activity and indicated complete sediment nitrification. There were measurable levels of ammonium, nitrite, and nitrate during free chlorine application, and nitrification activity gradually resumed upon a switch back to monochloramine. These findings suggest that the periodic removal of sediment from drinking water storage facilities is desirable to remove potentially protected environments for microorganisms.
储水罐中的沉积物可能会保护微生物免受消毒剂的暴露，从而导致水质恶化。然而，储水沉积物中的微生物活性和消毒剂渗透情况在很大程度上仍未得到充分描述。本研究使用微电极评估了一深 2 厘米（20000μm）的饮用水储水罐沉积物中一氯胺和游离氯的渗透情况。沉积物先后暴露于一氯胺 4 个月、游离氯 2 个月和一氯胺 2 个月。使用微电极获得了沉积物中时间相关的一氯胺、游离氯、溶解氧（DO）、pH 值、氨氮、亚硝酸盐和硝酸盐的分布情况。结果表明，并未观察到完全的一氯胺或游离氯渗透。同样，DO 也从未完全渗透到沉积物中，随着时间的推移，DO 向内渗透的最大深度为 10000μm，表明整个 8 个月内微生物活性持续存在。铵浓度的降低和硝酸盐浓度的增加，以及亚硝酸盐积累的最小化，进一步证明了微生物的活性，并表明了完全的沉积物硝化作用。在游离氯应用期间，存在可测量水平的氨氮、亚硝酸盐和硝酸盐，并且当再次切换回一氯胺时，硝化活性逐渐恢复。这些发现表明，从饮用水储存设施中定期去除沉积物是可取的，以去除微生物的潜在保护环境。
