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Seasonal Variations of Microbial Populations during Composting Processes of Municipal Solid Wastes

Shyamala D.C., Belagali S.L.

This study investigates the prevailing seasonal changes of physico-chemical and microbial community for mesophilic bacteria and fungi at different degradations stages of municipal solid wastes. The samples were collected from Excel plant (Vidyaranyapuram, Mysore) in different depths of pile during summer, rainy and autumn seasons in the year of 2011 to 2012 at once in 10 days intervals up to 60 days. Temperature and pH were measured by using standard method. The microbial analysis was done by serial dilution method and bacterial growth Nutrient agar (NA) and Czapek Dox Agar (CDA) for fungi enumeration. The pure cultures of the bacterial isolates were subjected to various morphological and biochemical characterization tests like, Catalase Test (CAT), Oxidase Test (OXT), Indole Test (INT), Methyl Red Test (MRT), Voges-Proskauer Test (VPT), Citrate Utilization Test (CUT), Urease Test (URT), Nitrate Reduction Test (NRT), Hydrogen Sulphide Production (H2S), Starch Hydrolysis Test (SHT) and Gelatine Hydrolysis Test (GHT) to determine the identity of the bacteria isolates. The results reveal that, the temperature of the windrows in all seasons reached maximum after 4 weeks of composting and then decreased by the end of the composting period (60 days). Marked changes in pH values of the composts in all seasons during degradation stages were found, but final stages shows the pH was at neutral except rainy season (60 days old compost sample with 8.7). The microbial populations were significant increase during initial stages of composting process and final stages pathogenic microbes was reduced, for all the three seasons. The Bacillus Sp., Pseudomonas and Asprigillus Sp., was dominate species during composting process. From the present investigation, it can be concluded that, the summer and autumn seasons microbial activities faster because the favourable environmental conditions for supporting the proper wastes degradation, therefore, these two seasons for obtained better quality of compost than rainy season.