Abeledo-Lameiro María Jesús, Ares-Mazás Elvira, Gómez-Couso Hipólito
Department of Microbiology and Parasitology, Faculty of Pharmacy, University of Santiago de Compostela, Campus Vida, 15782 Santiago de Compostela, A Coruña, Spain.
Department of Microbiology and Parasitology, Faculty of Pharmacy, University of Santiago de Compostela, Campus Vida, 15782 Santiago de Compostela, A Coruña, Spain.
J Photochem Photobiol B. 2016 Oct;163:92-9. doi: 10.1016/j.jphotobiol.2016.08.016. Epub 2016 Aug 12.
Cryptosporidium is a genus of enteric protozoan parasites of medical and veterinary importance, whose oocysts have been reported to occur in different types of water worldwide, offering a great resistant to the water treatment processes. Heterogeneous solar photocatalysis using titanium dioxide (TiO2) slurry was evaluated on inactivation of Cryptosporidium parvum oocysts in water. Suspensions of TiO2 (0, 63, 100 and 200mg/L) in distilled water (DW) or simulated municipal wastewater treatment plant (MWTP) effluent spiked with C. parvum oocysts were exposed to simulated solar radiation. The use of TiO2 slurry at concentrations of 100 and 200mg/L in DW yielded a high level of oocyst inactivation after 5h of exposure (4.16±2.35% and 15.03±4.54%, respectively, vs 99.33±0.58%, initial value), representing a good improvement relative to the results obtained in the samples exposed without TiO2 (51.06±9.35%). However, in the assays carried out using simulated MWTP effluent, addition of the photocatalyst did not offer better results. Examination of the samples under bright field and epifluorescence microscopy revealed the existence of aggregates comprising TiO2 particles and parasitic forms, which size increased as the concentration of catalyst and the exposure time increased, while the intensity of fluorescence of the oocyst walls decreased. After photocatalytic disinfection process, the recovery of TiO2 slurry by sedimentation provided a substantial reduction in the parasitic load in treated water samples (57.81±1.10% and 82.10±2.64% for 200mg/L of TiO2 in DW and in simulated MWTP effluent, respectively). Although further studies are need to optimize TiO2 photocatalytic disinfection against Cryptosporidium, the results obtained in the present study show the effectiveness of solar photocatalysis using TiO2 slurry in the inactivation of C. parvum oocysts in distilled water.
隐孢子虫是一类对医学和兽医学具有重要意义的肠道原生动物寄生虫，据报道其卵囊在全球不同类型的水中均有出现，对水处理过程具有很强的抵抗力。本研究评估了使用二氧化钛（TiO₂）悬浮液的异相太阳光催化对水中微小隐孢子虫卵囊的灭活效果。将含有微小隐孢子虫卵囊的蒸馏水（DW）或模拟城市污水处理厂（MWTP）出水与TiO₂（0、63、100和200mg/L）的悬浮液暴露于模拟太阳辐射下。在DW中使用浓度为100和200mg/L的TiO₂悬浮液，暴露5小时后卵囊灭活率较高（分别为4.16±2.35%和15.03±4.54%，初始值为99.33±0.58%），相较于未添加TiO₂的样品（51.06±9.35%）有显著改善。然而，在使用模拟MWTP出水进行的试验中，添加光催化剂并未取得更好的效果。在明场和落射荧光显微镜下检查样品发现，存在由TiO₂颗粒和寄生形式组成的聚集体，其尺寸随着催化剂浓度和暴露时间的增加而增大，而卵囊壁的荧光强度降低。光催化消毒过程后，通过沉淀回收TiO₂悬浮液可大幅降低处理后水样中的寄生虫负荷（DW中200mg/L的TiO₂和模拟MWTP出水中分别为57.81±1.10%和82.10±2.64%）。尽管需要进一步研究以优化TiO₂对隐孢子虫的光催化消毒效果，但本研究结果表明，使用TiO₂悬浮液的太阳光催化对DW中微小隐孢子虫卵囊具有灭活效果。
