Parallel experiments were carried out on two identical EGSB reactors, and the use of seed sludge came from the anoxic sludge of the municipal Sewage Treatment Plant and sludge concentration pond of the automobile painting wastewater treatment station respectively. And the both reactor were successfully started up after nearly 60 days of operation. At the same time, using high-throughput sequencing analysis, the results showed that a total of 20 phyla were observed in four samples, and the most

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... redominant phylum was Proteobacteria (23.3%), Bacteroidetes (30.4%), Firmicutes (47.1%) and Proteobacteria (70.5%) in FW, BW, CHW and CW, respectively. At the genus level, the superiority genera were T78, Anaerovorax, vadinCA02, E6, Clostridium, Longilinea, Tsukamurella, Blvii28, Methanosarcina, HA73, W22 and Fusibacter in the B reactor, and the superiority genera were HA73, Mycobacterium, Clostridium, Anaerovorax and Fusibacter in the C reactor. It is expected to provide theoretical support for practical engineering application of EGSB reactor Introduction With the development of economy, all kinds of pollution became more and more serious. While among the various treatment technologies, anaerobic treatment systems are being encouraged because of several advantages, including low construction costs, small land requirements, low excess sludge production, plain operation and maintenance, energy generation in the form of biogas [1] and robustness in terms of COD removal efficiency [2] , pH stability and recovery time [3, 4, 5] . A number of researchers have recommended anaerobic technology like expanded granular sludge bed (EGSB) reactor for the treatment of Urban sewage and industrial waste water [6] [7] [8] [9] [10] [11] [12] . The start-up of EGSB reactors is a complicated process and a number of factors, including wastewater characteristics, acclimatization of seed sludge, pH, nutrients, presence of toxic compounds, loading rate, upflow velocity (Vup), hydraulic retention time (HRT), liquid mixing and reactor design affect the growth of sludge bed [7, 13] . In the present study, two identical EGSB reactors was investigated by the use of seed sludge came from the anoxic sludge of the municipal Sewage Treatment Plant and sludge concentration pond of the automobile painting wastewater treatment station respectively. At the same time, the microbial communities of seeding source (FW, CHW), sludge samples(BW, CW) were investigated with the next generation sequences (NGS) tool.