Reza Barati Rashvanlou - Research Center for Environmental Health Technology, Iran University of Medical Sciences, Tehran, Iran.
Mahdi Farzadkia - Research Center for Environmental Health Technology, Iran University of Medical Sciences, Tehran, Iran.
Abbas Ali Moserzadeh - Civil Engineering, Department of Civil Engineering, Amirkabir University of Technology, Tehran
Asghar Riazati - Managing director of Tehran Water and Wastewater Co., Tehran, Iran.
Chiang Wei - Research Fellow/Division Chief Planning Division, The Experimental Forest, College of Bio-Resources and Agriculture, National Taiwan University, Nantou ۵۵۷۵۰, Taiwan
Edris Hoseinzadeh - Student Research Committee, Saveh University of Medical Sciences, Saveh, Iran.

Introduction: One of biological wastewater treatment methods that utilizes to both digesting waste activated sludge and methane production is anaerobic digestion (AD). It is believed to be most effective solution in terms of energy crisis and environmental pollution issues. Materials and Methods: In this study the sludge was digested anaerobically sampled from a full-scale WWTP, located at south of Tehran, Iran for evaluation. To study the microbial community within the sludge the MiSeq Sequencing method utilized. Based on our field data and microbial community data, a schematic diagram of probable leading pathways was made in the studied digester. Results: At first, the community variety in the bulk sludge and richness were enhanced followed by loading increasing. Meanwhile, the loading change enhanced the community richness and variety of the sludge. By comparing the rank-abundance distributions, a shallow gradient would show high evenness since the abundances of diverse species are alike. The results showed all the communities were extremely diverse and ۱۵ phyla were distinguished in the sludge sample. The dominant phyla of the community were Bacteroidetes and Firmicutes and quantity of the two phyla were ۲۱% and ۱۱%, respectively. Anaerobaculum, Acinetobacter, Syntrophomonas, and Coprothermobacter were the chief genera for the microbial communities and the sum of four genera were ۷%, ۳%, ۳%, and ۲%, respectively. Conclusion: It was shown that syntrophic acetate oxidizing bacterias (SAOBs) metabolized acetate through hydrogen trophic methanogenesis in the digester. Generally, the findings may be useful to help the wastewater operators to utilize an effective method that able to treat waste sludge plus methane production, simultaneously.

Microbial Community, Methane Production Pathway, Biogas, Anaerobic Digester.