Ultrasonic cavitation in hygienization surplus activated sludge

The success of an effective process of disintegration is the application of physical or chemical methods of the destruction of the celi wali which conseąuently becomes fragmented and the intracellular matters are released into the surrounding liquid. From the used methods of disintegration in the technology of sewage sludge positive results are achieved by: mechanical destructions, ultrasounds, heat treatments, adding of enzymes, ozone treatment, chemical dissolution by acidification or alkaline hydrolysis. The purpose of the conducted experiments was to demonstrate possibilities of application of the ultrasonic in the bacteriological hygienisation of surplus activated sludge. The confirmation of the effectiveness of the bactericidal activity of ultrasonic cavitation was the number of bacteria grown on agars before and after hygienisation process. Selcctive and basie beddings have been used in the research. The bacterial culture has lasted approximately 24 to 48 hours. After the period of ineubation the colonies produced have been counted and initially identified. Based on the microbiological analyses a significant reduction in an overall number of bacteria and pathogenic bacteria belonging to the family Enterobacteriaceae and to the pathogenic species Staphylococcus has been noticed. Reducing the number of Salmonella bacteria was 94 per cent at a frequency ultrasonic waves of 40 kHz and 89 per cent at 25 kHz. In the conducted processes of disintegration the dispersion of a solid phase of the sediment and also the destruction of pathogenic bacteria cells has been confirmed.