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Removal Mechanisms of Cryptosporidium Oocysts and Their Effective Treatment by Sand Filtration

隐孢子虫卵囊的去除机制及其砂滤的有效处理

基本信息

批准号：
10650536
负责人：
EBIE Kunio
金额：
$ 0.7万
依托单位：
Kitami Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

项目摘要

Outbreaks of waterborne cryptosporidiosis have often occurred since 1980s. It is pointed out that the removal rate of turbid matter by coagulation and sand filtration should be improved from 2.5-2.7log to 4.0log, in order to prevent the outbreaks.In the present study the fundamental experiments were conducted to elucidate the removal mechanisms of the oocysts by coagtilation and sand filtration, and fluorescent latex micro-beads were used as a surrogater of the oocysts. The findings of the experiments are as follows :(1) The behavior of zeta-potential of the beads with pH value was almost similar to that of the oocysts and kaolin particles. In addition, the characteristic of treatment of the beads was similar to that of kaolin particles, namely turbid matter.(2) In the filtration experiment, the method was newly developed to recover the beads inside the sand filter and in the effluent. The high recovery rates of 90.5-96.4% for the beads were obtained by using this method and it is effective to elucidate the removal mechanisms of the beads by sand filtration.(3) The filtration experiment demonstrated that many beads easily passed through the filter in the term of the initial breakthrough and that the beads leaked with the turbid matter retained inside the filter due to the acidification of the inlet water and a rise of the filtration rate.(4) In order to remove the oocysts effectively by the rapid sand filtration system, it is important to coagulate the turbid matter sufficiently and not to change the conditions of the inlet water and the filtration run. In addition it is necessary to coat the surface of the filter media with coagulants in order to improve the quality of the effluent throughout the filtration run.

自20世纪80年代以来，水媒隐孢子虫病经常发生。本文以荧光乳胶微球作为卵囊的替代物，对混凝-砂滤法去除卵囊的机理进行了初步研究。实验结果表明：（1）微珠的zeta电位随pH值的变化规律与卵囊和高岭土颗粒的zeta电位变化规律基本一致。此外，微珠的处理特性与高岭土颗粒相似，即浑浊物。(2)在过滤实验中，该方法是新开发的，以回收砂滤器内和流出物中的珠粒。用此方法可获得90.5-96.4%的高回收率，并可有效地阐明砂滤法去除微珠的机理。(3)过滤实验表明，许多珠容易通过过滤器在最初的突破和珠泄漏与混浊物质保留在过滤器内，由于进水的酸化和过滤速率的上升。(4)为了有效地去除卵囊，砂滤系统，重要的是要充分混凝的混浊物质，而不改变进水和过滤运行的条件。此外，有必要在过滤介质的表面涂上混凝剂，以提高整个过滤过程中的出水质量。