Influence of Ultrasonic Field Parameters on the Biochemical Activity of Leachates from the Composting Process

Reuse of leachates by recycling them for composting is part of the circular economy. However, directly returning compost leachates to the mixture might increase the concentration of contaminants in the stabilized mass. The application of the ultrasonic modification of leachate was aimed at increasing the activity of microorganisms and the availability of nutrients, and reducing the number of pathogenic species. The purpose of the work was to determine the impact of variable ultrasonic (time and amplitude) field parameters on the biochemical properties, and number of selected groups of microorganisms, of leachates from a composting process. The tests used short sonication times of 15, 30, 60, 90, and 120 s and vibration amplitudes of 15.25, 30.5, and 46 µm. The assessment was made on the basis of changes in numbers of microbial communities (mesophilic, thermophilic, Escherichia coli, Salmonella spp. and fungi) and enzymatic activity (dehydrogenases-DHA), as well as respiratory activity (AR). Based on the conducted research, it was found that the leachate sonication time of 60 s and amplitude 30.5 µm were the most effective. The above parameters were considered borderline, above which there were no significant differences in the values of the analyzed indicators.