MONITORING THE SURVIVABILITY OF Escherichia coli AND Salmonella spp. IN ANAEROBIC CO-DIGESTION OF CATTLE RUMEN CONTENT AND FOOD WASTE

ABSTRACT
In this study, the survivability of E. coli and Salmonella spp. during anaerobic co-digestion of cattle rumen content and food waste to establish the effect of inoculum on the co-digestion process was investigated. The inoculum fluid was obtained from the rumen of a newly slaughtered cattle. The experiment was performed under mesophilic conditions using air-tight gas cylinder as batch anaerobic digester. The study revealed that the lag phase was less than a day with almost immediate biogas production but with very low methane composition. The production improved significantly after the first ten days of digestion and peaked on the fifteenth day with over 15 litres of biogas produced. The production climaxed by the end of the third week of production accounting for over 97% of the total solids (TS) used-up during the whole digestion period. E. coli showed great adaptability in the medium as the population of E. coli averagely increased with decrease in pH. However, Salmonella spp. was below detectable limit during the whole period of study. From this study, we could see that mesophilic anaerobic co-digestion of cattle rumen content and food waste with about neutral initial pH or less results in a high sanitation efficiency for Salmonella spp. but not for than E. coli.