Comparison of microbial activity of selected biopreparations and leachates for composting

The aim of this study was to compare the effectiveness of selected commercial biopreparations (Radivit, DBC Plus L, DBC Plus R5) and leachates, prepared using with the usage of ultrasounds with low frequencies and short exposure times. The comparison was made based on the qualitative and quantitative analysis of microbial communities and enzymatic activity, and, in the case of sonicated leachates, based on respiratory activity. It was found based on the results of enzymatic analysis that among the tested commercial biopreparations, Radivit may be the most useful for intensification of the composting process. Sonication of leachates resulted in an increase in the number of microorganisms and, to a small extent, in higher enzymatic activity, and respiratory activity. Furthermore, it was found that the leachates sonication time of 15 s was the most effective. The stated value of the sonification time was considered to be borderline, above which no significant changes in the value of the analyzed indicators were recorded. In the case of mesophilic bacteria in the leachate after 15 s of sonication, an increase in the number of 50 CFU/cm3 (colony forming units) was obtained in relation to the unsaturated leachate. For thermophilic bacteria, an increase of almost 200 CFU/cm3 compared to the control sample was noted. In the case of respiratory activity, a 47% increase was obtained after sonication of the leachate for 15 s. Lengthening of the sonication time did not increase the leachate respiratory activity.