Development criteria for ultraviolet disinfection of unfiltered drinking water

紫外线（UV）光已被证明对隐孢子虫和贾第鞭毛虫等水生寄生虫有效，并迅速被用于过滤饮用水的水处理消毒。由于人们对水中的颗粒和其他杂质对紫外线消毒效果的影响知之甚少，因此对未经过滤的地表水等质量差的水源使用紫外线的方法受到了限制。拟议研究的广泛目标是提高对水质变量（如微生物浓度、颗粒物、溶解和胶体有机物）如何影响未经过滤的天然水中微生物的紫外线消毒的认识。隐孢子虫卵囊、枯草芽孢杆菌孢子和其他替代微生物与未过滤的天然水和合成水基质中存在的颗粒的聚集和相互作用将在实验室实验中进行研究。还将开发一种对含有低浓度种子微生物的水样进行紫外线照射的方法。由于隐孢子虫的研究非常昂贵和困难，替代微生物将用于紫外线灭活研究。替代微生物在各种未经过滤的天然水和合成水基质中的聚集和颗粒相互作用将被测量，并与在台式紫外线照射实验中测量的失活水平相关联。这项研究的预期最终结果是一个水质指数或一个方便的标准测试，水处理工程师可以使用它来预测使用紫外线对特定未经过滤的供水进行消毒时提供的公共卫生保护水平。

Ultraviolet (UV) light has been shown to be effective against waterborne parasites such as Cryptosporidium and Giardia and is rapidly being adopted in water treatment for disinfection of filtered drinking water.   The use of UV for poor quality water sources, such as unfiltered surface water, has been limited because the effect of particles and other impurities in the water on the effectiveness of UV disinfection is poorly understood.   The broad objective of the proposed research is to improve the knowledge of how water quality variables such as microorganism concentration, particulate matter, and dissolved and colloidal organic matter, affect UV disinfection of microorganisms unfiltered natural water.  Aggregation and interaction of Cryptosporidium oocyst, Bacillus subtilis spores and other surrogate microorganisms with particles present in unfiltered natural water and synthetic water matrices will be investigated in laboratory experiments.  A method for conducting UV exposures with water samples containing low concentrations of seeded microorganisms will also be developed.   Because research with Cryptosporidium is very expensive and difficult, surrogate microorganisms will be used for UV inactivation studies.   Aggregation and particle-interaction of surrogate microorganisms in a variety of unfiltered natural water and synthetic water matrices will be measured and correlated with the level of inactivation measured in bench-top UV exposure experiments.  The anticipated end product of this research is a water quality index or a convenient standard test that could be used by water treatment engineers to predict the level of public health protection provided when UV is used to disinfect specific unfiltered water supplies.