NSERC Industrial Chair on Drinking Water, Ecole Polytechnique de Montreal, Department of Civil, Geological, and Mining Engineering, P.O. Box 6079, Downtown Station, Montreal, Quebec H3C 3A7, Canada.
Water Res. 2010 Feb;44(4):1072-81. doi: 10.1016/j.watres.2009.09.001. Epub 2009 Sep 4.
The significance of zooplankton in the transport and fate of pathogenic organisms in drinking water is poorly understood, although many hints of the role of predation in the persistence of microorganisms through water treatment processes can be found in literature. The objective of this study was to assess the impact of predation by natural zooplankton on the transport and fate of protozoan (oo)cysts in granular activated carbon (GAC) filtration process. UV-irradiated unlabelled Cryptosporidium parvum and Giardia lamblia (oo)cysts were seeded into two pilot-scale GAC filtration columns operated under full-scale conditions. In a two-week period after seeding, a reduction of free (oo)cysts retained in the filter bed was observed. Zooplankton was isolated from the filter bed and effluent water on a 30 microm net before and during the two-week period after seeding; it was enumerated and identified. Rotifers, which are potential predators of (oo)cysts, accounted for the major part of the isolated zooplankton. Analytical methods were developed to detect (oo)cysts internalized in natural zooplankton isolated from the filter bed and effluent water. Sample sonication was optimized to disrupt zooplankton organisms and release internalized microorganisms. (Oo)cysts released from zooplankton after sonication were isolated by IMS and stained (EasyStain) for microscopic counting. Both Cryptosporidium and Giardia (oo)cysts were detected in association with zooplankton in the filter bed samples as well as in the effluent of GAC filters. The results of this study suggest that predation by zooplankton can play a role in the remobilization of persistent pathogens such as Cryptosporidium and Giardia (oo)cysts retained in GAC filter beds, and consequently in the transmission of these pathogens in drinking water.
浮游动物在饮用水中病原生物的迁移和归宿中的作用尚未被充分了解，尽管文献中已经有许多关于捕食作用在微生物通过水处理过程中持续存在的作用的暗示。本研究的目的是评估天然浮游动物捕食作用对颗粒活性炭（GAC）过滤过程中原生动物（卵）囊迁移和归宿的影响。用紫外线照射未标记的隐孢子虫和蓝氏贾第鞭毛虫（卵）囊，将其接种到两个按全规模条件运行的中试规模 GAC 过滤柱中。在接种后两周内，观察到过滤床中自由（卵）囊的减少。在接种前后的两周内，用 30 微米的网从过滤床和出水中分离浮游动物，并对其进行计数和鉴定。轮虫是（卵）囊的潜在捕食者，它们占所分离浮游动物的主要部分。开发了分析方法来检测从过滤床和出水中分离的天然浮游动物中内化的（卵）囊。优化了样品超声处理，以破坏浮游动物生物并释放内化的微生物。用 IMS 分离超声处理后从浮游动物中释放的（卵）囊，并对其进行染色（EasyStain）进行显微镜计数。在过滤床样本以及 GAC 过滤器的出水中，都检测到了隐孢子虫和贾第鞭毛虫（卵）囊与浮游动物相关联。本研究的结果表明，浮游动物的捕食作用可能在 GAC 过滤床中保留的持久性病原体（如隐孢子虫和贾第鞭毛虫）的再移动以及这些病原体在饮用水中的传播中发挥作用。
