CHANGES TO THE MICROBIAL ECOLOGY IN ANAEROBIC DIGESTERS TREATING ICE-CREAM WASTE-WATER DURING START-UP

Changes to the microbial ecology in four different designs of pilot-scale, high rate anaerobic reactor, treating a synthetic ice cream waste, were studied during the initial start-up phase. The nature of the biomass and the numbers of non-methanogenic and methanogenic bacteria remained similar in all the digesters. Variations within the bacterial populations did occur but statistical analysis showed no significant difference between the numbers in each reactor and with respect to time after start-up. Within the fluorescent methanogen population, selection an organism tentatively identified as either Methanobacterium formicicium or a species of Methanobrevibacter occurred. Reactor design did not appear to be as important as the wastewater composition in causing changes to the microbial communities. The problems of using conventional microbial enumeration methods in the study of complex microbial communities such as digester sludge are also discussed.