Microbiological indexes have been studied in dynamics at lime treatment and independent planting of lavender (Lavandula angustifolia, variety “Hemus”) and sweet basil (Ocimum basilicum, variety “Genovese”) of fresh sludges from a purification plant, with concentrations of quicklime: 10%, 20% and 30% for a 40-day period of composting. The microbiological analysis includes determining of nonpathogenic (non-spore forming bacteria, bacilli, actynomycetes, micromycetes, bacteria, which assimilate mineral nitrogen) and pathogenic (Salmonella spp., Escherichia coli and coliforms, Enterococcus, Clostridium perfringens) microflora. Out of the beneficial microflora in the sludges the quantity of the non-spore forming bacteria is the biggest, and the lowest is of the actynomycetes. A basic share in the composition of the pathogenic microflora occupies Clostridium perfringens, followed by Escherichia coli and coliforms, and Enterococcus. Absence of Salmonella spp. was established in the studied sludges. The best results for the disinfection of the sludges displays the adding of 30% quicklime (followed by the variants with 20% and 30% lime), on 5-th day of the experiment setting. The pH decrease in the period of the study leads to a repeated development of pathogenic microflora. In the meantime the creation of an alkaline medium leads to decrease in the quantity of the beneficial microorganisms. The decrease of the moisture and the drying of the sludges for the study period display a weaker effect on the dynamics of the microflora in comparison with the pH increase impact. The planting of lavender and basil independently in the sludges samples from a purification plant has a beneficial effect (a little bit better with the lavender variants) for increase of the quantity of nonpathogenic microbes and pathogens frequency of occurrence decrease. The effect is intensified by increasing the plant development period.