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

Monitoring of indicator and pathogenic microorganisms isessential for proper composting. The aim of this study was to evaluate thechange in population of coliformbacteria and Salmonellaspp. in composting process of municipal wastes andafter its application on soil. The samples were taken from each raw waste pile، initial pile، active phasepile، cooling phase pile and the final product in December، January and February. Samples were analyzed for temperature، moisture، C/N، pH، total and fecalcoliforms and Salmonella spp. To evaluate the condition of applied compost on soil، 5kg of compost was spread on the soil and sampling، physicochemicaland biological experiments were performed at intervals of 5 days up to 20 days after use. The minimum andmaximum temperatures were related to raw waste and thermophilic phase with 22°C and 61°c، respectively. Average total and fecal coliforms from 1. 71×107 and 1. 02×107 MPN/g DW in the raw wastewas reduced to 2. 3×103 and1. 18×103 in the final product، respectively. Salmonella spp wasalso reduced from 415 MPN/gDW at beginning of the compostingprocess to 28 MPN/g DWin the final product. After compost application، total and fecal coliformpopulations decreased and on day 20 reached to 150 and 18 MPN/gDW،respectively. Salmonella spp. also decreased to about zero by day 5-10. Theresults of this study revealed thatthermophilic stage has the greatest impact on coliformbacteria، and Salmonella spp. are the most affected by thestabilization phase. But considering the contamination ofapplied compost because of high levelsof fecal coliform and salmonella compared to standard values، theappropriate interval between compost application and harvest should be considered for crops that are incontact with soil.