evaluate the change in population of coliform bacteria and salmonella spp. in composting process of municipal wastes

background: monitoring of indicator and pathogenic microorganisms is essential for proper composting. the aim of this study was to evaluate the change in population of coliform bacteria and salmonella spp. in composting process of municipal wastes and after its application on soil. methods: the samples were taken from each raw waste pile, initial pile, and active phase pile, cooling phase pile and the final product in december, january and february. samples were analyzed for temperature, moisture, c/n, ph, total and fecal coliforms and salmonella spp. to evaluate the condition of applied compost on soil, 5 kg of compost was spread on the soil and sampling, physicochemical and biological experiments were performed at intervals of 5 days up to 20 days after use. findings: the minimum and maximum temperatures were related to raw waste and thermophilic phase with 22 °c and 61°c, respectively. average total and fecal coliforms from 1.71×10 7 and 1.02×10 7 mpn/g dw in the raw waste was reduced to 2.3×10 3 and 1.18×10 3 in the final product, respectively. salmonella spp was also reduced from 415 mpn/gdw at beginning of the composting process to 28 mpn/g dw in the final product. after compost application, total and fecal coliforms populations decreased and on day 20 reached to 150 and 18 mpn/gdw, respectively. salmonella spp. also decreased to about zero by day 5-10. conclusion: the results of this study revealed that thermophilic stage has the greatest impact on coliform bacteria, and salmonella spp. are the most affected by the stabilization phase. however, considering the contamination of applied compost because of high levels of fecal coliforms and salmonella compared to standard values, the appropriate interval between compost application and harvest should be considered for crops that are in contact with soil.