National Institute of Water and Atmospheric Research Ltd (NIWA), P. O. Box 11-115, Hamilton, New Zealand.
Environmental Science Research (ESR), Christchurch Science Centre, 27 CreykC Road, Ilam, PO Box 29181, Christchurch, 8540, New Zealand.
J Environ Manage. 2021 May 15;286:112197. doi: 10.1016/j.jenvman.2021.112197. Epub 2021 Feb 23.
This study compared light and dark disinfection of faecal bacteria/viral indicator organisms (E. coli and MS2 (fRNA) bacteriophage) and human viruses (Echovirus and Norovirus) in Wastewater Treatment Pond (WTP) mesocosms. Stirred pond mesocosms were operated in either outdoor sunlight-exposed or laboratory dark conditions in two experiments during the austral summer. To investigate wavelength-dependence of sunlight disinfection, three optical filters were used: (1) polyethylene film (light control: transmitting all solar UV and visible wavelengths), (2) acrylic (removing most UVB <315 nm), and (3) polycarbonate (removing both UVB and UVA <400 nm). To assess different dark disinfection processes WTP effluent was treated before spiking with target microbes, by (a) 0.22 μm filtration to remove all but colloidal particles, (b) 0.22 μm filtration followed by heat treatment to destroy enzymes, and (c) addition of Cytochalasin B to supress protozoan grazing. Microbiological stocks containing E. coli, MS2 phage, Echovirus, and Norovirus were spiked into each mesocosm 10 min before the experiments commenced. The light control exposed to all sunlight wavelengths achieved >5-log E. coli and MS2 phage removal (from ~1.0 × 10 to <1 PFU/mL) within 3 h compared with up to 6 h in UV-filtered mesocosms. This result confirms that UVB contributes to inactivation of E. coli and viruses by direct sunlight inactivation. However, the very high attenuation with depth of UVB in WTP water (99% removal in the top 8 cm) suggests that UVB disinfection may be less important than other removal processes averaged over time and full-scale pond depth. Dark removal was appreciably slower than sunlight-mediated inactivation. The dark control typically achieved higher removal of E. coli and viruses than the 0.22 μm filtered (dark) mesocosms. This result suggests that adsorption of E. coli and viruses to WTP particles (e.g., algae and bacteria bio-flocs) is an important mechanism of dark disinfection, while bacteria and virus characteristics (e.g. surface charge) and environmental conditions can influence dark disinfection processes.
本研究比较了粪便细菌/病毒指示生物（大肠杆菌和 MS2（fRNA）噬菌体）和人类病毒（肠病毒和诺如病毒）在污水处理池塘（WTP）中光和暗消毒的效果。在两个实验中，在澳大利亚夏季，在户外阳光暴露或实验室黑暗条件下分别对搅拌池塘中进行了研究。为了研究阳光消毒的波长依赖性，使用了三种光学过滤器：（1）聚乙烯薄膜（仅控制：透射所有太阳紫外线和可见光波长）；（2）压克力（去除大部分 UVB <315nm）；（3）聚碳酸酯（同时去除 UVB 和 UVA <400nm）。为了评估不同的暗消毒过程，在向目标微生物中添加之前，用 WTP 出水进行预处理：（a）0.22μm 过滤以去除所有胶体颗粒；（b）0.22μm 过滤后热处理以破坏酶；（c）添加细胞松弛素 B 以抑制原生动物摄食。含有大肠杆菌、MS2 噬菌体、肠病毒和诺如病毒的微生物库存物在实验开始前 10 分钟被添加到每个中。暴露于所有阳光波长的光控制在 3 小时内实现了 >5-log 大肠杆菌和 MS2 噬菌体的去除（从~1.0×10 到 <1PFU/mL），而在 UV 过滤的中则需要长达 6 小时。该结果证实了 UVB 通过直接阳光失活对大肠杆菌和病毒的灭活作用。然而，WTP 水中 UVB 的深度衰减非常高（顶部 8cm 中去除 99%），这表明 UVB 消毒可能不如随时间和全池塘深度平均的其他去除过程重要。黑暗去除明显比阳光介导的失活动慢。黑暗对照通常比 0.22μm 过滤（黑暗）对照中实现了更高的大肠杆菌和病毒去除。该结果表明，大肠杆菌和病毒吸附到 WTP 颗粒（例如藻类和细菌生物絮体）是黑暗消毒的重要机制，而细菌和病毒特性（例如表面电荷）和环境条件可以影响黑暗消毒过程。
