EFFECT OF TANK DESIGN AND TWO-PHASED FILTRATION ON CLEANLINESS LEVEL OF WATER HYDRAULIC SYSTEM

摘要

Filtration in water hydraulic system may be problematic, due to chemical, physical and biological contamination. This contamination may cause quick increase in the pressure difference over the filter element. The aim of this research was to test different kinds of tank sizes and filter combinations and to determine their effects on water quality in a water hydraulic system. In this paper the results of these experiments are presented. Experiments were made with pilot-scale water hydraulic systems. The systems induced no biological contamination and only a minimum amount of physical and chemical contamination. Filtered tap water was used as a pressure medium. The tested filter ratings (β>5000) were from 10 to 90μm depth type elements and the three different tank sizes 62, 105 and 148 litres. Experiments were made with water without amendments, and water with nutrient and particle contamination. The test periods were up to four weeks. Pressure difference over the filter, fluid flow and temperature are monitored. Microbiological analyses consisted of total number of cells, heterotrophic viable plate counts and the determination of biofilm formation. In addition, dissolved organic carbon concentration and particle counts were determined. Solving the microbiological problems of water hydraulics requires new approach to tank design methods that support the long-term working of the water hydraulic system. It is possible to (1) reduce microbial growth in water and on surfaces with a proper tank design, (2) keep microbial growth under control and (3) considerably extend the filter lifetimes by using twophased filtration in water hydraulic systems.