Aerobic Activated Sludge Treatment of High-Salinity Chlorophenolic Wastewater and Community Structure Analysis

The activated sludge dominated by moderately halophilic bacteria were acclimated using SBR reactor, which used to remove the 2-chlorophenol (2-CP) efficiently from wastewater. When the mass concentration of NaCl was between 10 g/L and 80 g/L, the removal rates of both 2-CP and COD reached 91%. When the mass concentration of NaCl was 80 g/L and the 2-CP mass concentration was above 1 000 mg/L, the removal rate of 2-CP could maintain at 98%, in which the SBR reactor achieved the best treatment effect. The concentration of extracellular polymers (EPS) of activated sludge reached the highest amount of 142. 6 mg/g at this operation condition. With the increase of salinity, the amount of polysaccharide in EPS increased. As observed by using microscope and scanning electron microscopy (SEM), most of the microorganisms appeared pellets and the microbial community had a tendency to gather spontaneously under the high salinity condition. 16S rRNA gene clone library analysis showed that the dominated bacterial population in the activated sludge was Alcaligenes faecalis which belonged to Proteobacteria. PCR and sequence analysis of the key enzyme gene in 2-CP degradation showed that hydroxylase, chlorinated catechol 1, 2-dioxygenase and chlorinated catechol 2, 3-dioxygenase co-existed in the activated sludge system, which indicated the diverse 2-CP degradation pathway.