EFFECTS OF MICROBIAL GROWTH AND PARTICLES ON FILTRATION IN WATER HYDRAULIC SYSTEM

摘要

Filtration in water hydraulic systems may be very problematic, due to physical and biological contamination. This contamination may cause quick increase in the pressure difference over the filter element thus, the aim of this research was to test depth type filter and determine the effects of microbial growth and particulate contamination on filtration in a water hydraulic system. In this paper the results of these experiments are presented. Experiments were made with a pilot-scale water hydraulic system, which induces no biological contamination and only a minimum amount of particulate contamination. Filtered tap water was used as a pressure medium. Tested depth type filter element had a filter rating (β＞5000) of 10μm. Test periods were three weeks. Pressure difference over the filter, fluid flow and temperature were monitored. Microbial analyses consisted of determinations of the total number of cells, heterotrophic viable plate counts and concentration of dissolved organic carbon. Slight microbial or particulate contamination is not a serious problem considering the lifetime of the filter element. When microbial and particulate contamination occurred at the same time, the situation became much more complicated. In this situation microbial growth prevented the normal operation of depth type filter element.