© 2019, International Centre for Sustainable Development of Energy, Water and Environment Systems SDEWES. All rights reserved. A highly complex microbial community involved in anaerobic sludge digesters plays vital roles in sludge treatment. The data on microbial ecology is important to accomplish efficient operation of the anaerobic digesters. This study is aimed at monitoring the bacterial community of three full-scale anaerobic digesters of a full-scale municipal wastewater treatment Plant in Dubai, United Arab Emirates. Fluorescent in-situ hybridization technique was applied to identify the bacterial groups and quantitative polymerase chain reaction to compare the richness of bacterial and archaeal domain. Results of the fluorescent in-situ hybridization technique analysis showed that the phylum Proteobacteria was most abundant followed by cytophage-Flavobacterium group of Bacteroides, Firmicutes and Actinobacteria. Among proteobacterial subclass Delta- and Alpha- were dominating than Gamma- and Beta-proteobacteria. The genus Desulfobacter and Desulfobacterium were the dominant groups hybridizing 70-76% of total 4', 6'- diamidino - 2 phenylindole stained cells. The quantitative polymerase chain reaction results showed that Bacterial domain was dominating in all three digesters compared to the archaeal domain.