Microbial disinfection capacity of municipal solid waste (MSW) composting

Abstract

The disinfection capacity of a municipal solid waste (MSW) composting plant (Siloda®) has been evaluated. In spring and summer, MSW was followed during the composting process from raw material to mature compost and long- term storage (1 year). Ascaris eggs, Salmonella, Shigella, total streptococci, faecal streptococci, total coliforms, faecal coliforms and Escherichia coli were studied. Disinfection was successful in terms of a decrease in faecal contamination indicators and disappearance of faecal pathogens. Faecal coliform concentrations in raw waste reached 2.1 x 108 cfu g-1 dry weight in spring (CI 95%: 5.2 x 107-3.4 x 108) and 7.2 x 108 cfu g-1 dry weight (1 x 108-1.7 x 109) in summer, and fell to less than 100 cfu g-1 dry weight within 20 d. Faecal streptococci concentrations reached 8.7 x 108 cfu g-1 dry weight (3.7 x 108-1.3 x 109) in spring and 2.0 x 109 cfu g-1 dry weight (5.6 x 108-3.4 x 109) in summer, and fell to 8.7 x 104 cfu g-1 dry weight (6.9 x 104-1.0 x 105). No seasonal pattern of contamination, mainly of animal origin, was observed. Microbiological quality of finished compost depends on the storage conditions. Therefore, the storage stage should be viewed as part of the composting process. Monitoring disinfection capacity of MSW composting needs to combine several microbial populations.