Microbial survival, maturity and health hazards in different composting systems

Thumbnail Image
Journal Title
Journal ISSN
Volume Title
Temperature, moisture and pH are known parameters that affect compost microbial community, maturity and quality, but vary in different systems. In assessing the efficiency of composting systems, the need to produce quality compost devoid of pathogenic microorganisms that pose health hazards in the food chain is very important. Temperature, moisture and pH development in four composting systems were studied for thirteen weeks to assess their effects on total viable count, total coliform count, total fungi count, helminth eggs count and germination index. ANOVA preformed on temperature values recorded in the different systems were significantly different as p-value yielded 4.75 x 10-7. However the moisture and pH values recorded were not significantly different as these gave p-values of 0.9842 and 0.0632 respectively. P-values for total viable count, total coliform count, total fungi count and germination indices in the different systems yielded 0.027, 0.9994, 0.9681 and 0.0904 respectively. No helminth eggs were seen in all the systems. Generally, the total viable count reduced while total fungi increased at the end of week 12 in all systems. However, total coliform reduced to 0 during week 4.The pH values of compost masses ranged between 7 and 9 whereas moisture reduced from the range of 61% - 72 % to 40% - 60% from week 4 to week 12 in all systems. Temperatures recorded in DAT and HV systems were higher than those recorded in FA and T-W systems during the process. The lowest temperatures were recorded in FA allowing more microorganisms to survive in it. Bacteria such as Staphylococcus spp., Streptococcus spp., Bacillus spp., Corynebacterium spp., Yersinia spp., Listeria spp., Campylobacter spp., Enterobacter spp. and Clostridium spp. were identified in the systems. Penicillium spp., Aspergillus spp., Mucor spp. and Rhizopus spp. were the fungi identified. Bacillus spp. and Corynebacterium spp., present in a starter added to the compost masses in each system to facilitate the decomposition, survived in all the systems. Other microorganisms such as Listeria spp., Staphylococcus spp., Penicillium spp. and Mucor spp. survived the process in some of the systems. Listeria spp., Penicillium spp. and Staphylococcus spp. are known to cause diseases in humans. The final germination indices recorded were 189.54%, 198.11%, 202.83% and 222.64% in DAT, HV, FA and T-W systems respectively indicating the measure of compost maturity in the systems.
A Thesis submitted to the Department of Agricultural Engineering, Kwame Nkrumah University of Science and Technology, Kumasi in partial fulfillment of the requirements for the degree of Master of Science,2009