Tufenkji Nathalie, Dixon David R, Considine Robert, Drummond Calum J
Department of Chemical Engineering, McGill University, Montreal, Que., Canada H3A2B2.
Water Res. 2006 Oct;40(18):3315-31. doi: 10.1016/j.watres.2006.07.036. Epub 2006 Sep 18.
Owing to its widespread occurrence in drinking water supplies and its significant resistance to environmental stresses, Cryptosporidium parvum is regarded as one of the most important waterborne microbial parasites. Accordingly, a substantial research effort has been aimed at elucidating the physical, chemical and biological factors controlling the transport and removal of Cryptosporidium oocysts in natural subsurface environments and drinking water treatment facilities. In this review, a multi-scale approach is taken to discuss the current state-of-knowledge on Cryptosporidium-sand interactions at a nano-scale, bench-scale and field-scale relevant to water treatment operations. Studies conducted at the nano-scale and bench-scale illustrate how techniques based on the principles of colloid and surface chemistry are providing new insights about oocyst-sand interactions during transport of Cryptosporidium oocysts in granular porous media. Specifically, atomic force microscopy and impinging jet experiments reveal the importance of oocyst surface biomolecules in controlling Cryptosporidium/sand interactions by a mechanism of steric hindrance. Traditional bench-scale column transport studies conducted over a broad range of experimental conditions highlight the role of physicochemical filtration and physical straining in the removal of oocysts from the pore fluid. Such experiments have also been used to evaluate the influence of biofilms formed on grain surfaces and the presence of natural organic matter on oocyst-sand interactions. Whilst filtration studies conducted at the plant-scale have been useful for evaluating the effectiveness of various materials as surrogates for Cryptosporidium oocysts, at this macro-scale, little could be learnt about the fundamental mechanisms controlling oocyst-sand interactions. This review of the literature on Cryptosporidium-sand interactions at different length scales points to the importance of combining studies at the plant-scale with well-controlled investigations conducted at the nano- and bench-scales. Furthermore, because oocyst surface properties play an important role in controlling the extent of interaction with sand surfaces, a thorough discussion of Cryptosporidium oocyst characteristics and electrical properties is presented.
由于微小隐孢子虫在饮用水源中广泛存在且对环境压力具有显著抗性，它被视为最重要的水源性微生物寄生虫之一。因此，大量研究工作致力于阐明控制微小隐孢子虫卵囊在天然地下环境和饮用水处理设施中迁移与去除的物理、化学和生物因素。在本综述中，采用多尺度方法来讨论与水处理操作相关的纳米尺度、实验室规模和现场规模下微小隐孢子虫与沙子相互作用的当前知识状态。在纳米尺度和实验室规模下进行的研究表明，基于胶体和表面化学原理的技术如何为微小隐孢子虫卵囊在颗粒多孔介质中迁移过程中的卵囊 - 沙子相互作用提供新的见解。具体而言，原子力显微镜和冲击射流实验揭示了卵囊表面生物分子通过空间位阻机制控制微小隐孢子虫/沙子相互作用的重要性。在广泛的实验条件下进行的传统实验室规模柱迁移研究突出了物理化学过滤和物理截留在从孔隙流体中去除卵囊方面的作用。此类实验还用于评估颗粒表面形成的生物膜以及天然有机物的存在对卵囊 - 沙子相互作用的影响。虽然在工厂规模下进行的过滤研究对于评估各种材料作为微小隐孢子虫卵囊替代物的有效性很有用，但在这个宏观尺度上，关于控制卵囊 - 沙子相互作用的基本机制了解甚少。本对不同长度尺度下微小隐孢子虫 - 沙子相互作用文献的综述指出了将工厂规模的研究与在纳米和实验室规模下进行的严格控制的研究相结合的重要性。此外，由于卵囊表面性质在控制与沙子表面相互作用的程度方面起着重要作用，因此对微小隐孢子虫卵囊特征和电学性质进行了全面讨论。
