[Effects of Salinity on the Operation of EGSB Reactors and the Anaerobic Granular Sludge]

The existence of high concentrations of salinity and organics would have a great impact on the microorganisms when using bioreactors to treat wastewater. Thus, it is necessary to find bioreactors resistant to high concentrations of salinity. The effect of salinity on an expanded granular sludge bed reactor (EGSB) was studied by increasing the Cl^- concentration from 0 to 10000 mg·L^-1 using simulated high salinity wastewater with a COD volume loading of 3.267 kg·(m³·d)^-1. The results show no obvious inhibitory effect of Cl^- on the microorganism when the concentration of Cl^- was below 7500 mg·L^-1. Above 1.3 m³·(m³·d)^-1 volumetric gas production rate was maintained and COD removal rate could achieved 98.1% when the Cl^- concentration up to 7500 mg·L^-1 while the large particle size of anaerobic granular sludge occupying the majority of of the system. The anaerobic granular sludge was seriously affected when the Cl^- concentration as 10000 mg·L^-1. The community structure of the anaerobic granular sludge was analyzed using high-throughput sequencing when the Cl^- concentration was 0 and 5000 mg·L^-1. The results show that the salinity stress produced different dominant groups. The dominant species were Methanobacterium, Methanospirillum, Methanothrix, and Paludibacter when the Cl^- concentration was 5000 mg·L^-1, but Methanoregula and Longilinea were the dominant species when the Cl^- concentration was 0.