Performance robustness of the UASB reactors treating saline phenolic wastewater and analysis of microbial community structure

Anaerobic digestion was an important way to remove phenols from saline wastewater; however the anaerobic microorganisms were adversely affected by high concentration of salts. In order to clarify the performance robustness and microbial community structure for anaerobic digestion of saline phenolic wastewater, the UASB reactors were compared to treat phenolic wastewater under saline and non-saline conditions. The saline reactors were operated stably with phenols concentration increasing from 100 to 500mgL^-1 at 10g Na⁺ L^-1. The robustness of the saline reactors was weakened at 1000mg phenols L^-1 and 10g Na⁺ L^-1. However, the substrate utilization rates (SURs) for phenol, catechol, resorcinol, hydroquinone, and the specific methanogenic activity (SMA) of sludge were decreased by 95%, 85%, 97%, 78%, and 68%, respectively with phenols concentration enhancing from 1000 to 2000mgL^-1. Moreover, the SURs for phenol, catechol, resorcinol, hydroquinone, and the SMA of sludge were reduced by 32%, 65%, 74%, 45%, and 59%, respectively with Na⁺ concentration increasing from 10 to 20gL^-1, in comparison with the values obtained at 10g Na⁺ L^-1 and 1000mg phenols L^-1. Finally, the analysis of microbial community structure demonstrated that phenols degraders were less tolerant to high concentrations of Na⁺ and phenols than methanogens.