Filters and microbial growth in water hydraulic system

To study survival and growth of microbes and filtration in water hydraulic system. two experiments with a pilot-scale water hydraulic system were done. in the experiments, two commercially available filter elements were examined. The pressure medium contained DOC 3 mg/L and BDOC 1 mg/L. During the pilot operation, DOC and BDOC concentrations increased to 5 and 3 mg/L, respectively. This indicates dissolution of organic compounds from the system components. Viable counts of bacteria, as measured on R2A medium, increased from 10(2) to over 10(4) cfu/mL during the first 3 days of operation and gradually decreased to below 104 cfu/mL during the following three weeks. The bacteria grew slower on R2A at 20 degrees C than at 35 degrees C which was the operation temperature of the pilot system. Number of solid matter particles, as analysed by membrane counting, varied, being almost random, during tests. Test results indicate that the performance of both filters is very different from the filters in oil hydraulics and suggest that the filter clogging is also a microbiological and a chemical phenomenon in the water hydraulic systems.