Aerobic Activated Sludge Treatment Of High-Salinity Chlorophenolic Wastewater And Community Structure Analysis

This study acclimated the activated sludge dominated by moderately halophilic bacteria using SBR reactor, which removed the 2-chlorophenol (2-CP) efficiently. When the concentration of 2-CP was below 200 mg/L, the SBR reactor with operation period of 12 h could remove over 90% 2-CP. As the concentration of 2-CP increased to 200 mg/L, the removal rate of 2-CP decreased from 90% to 67% and of COD decreased from 87% to 61%. The removal rate of 2-CP by activated sludge increased to 92% by extending the operation period to 36 h. And the removal rate of 2-CP could maintain over 90% when the concentration of 2-CP increased to 400 mg/L at this operation condition. The results showed that the activated sludge could adapt to high salinity condition through a period domestication. When the concentration of NaCl was between 10 g/L to 80 g/L, the removal rates of 2-CP and COD reached to 91%. The sludge settlement ratio (SV30) decreased with the increase of salinity. The value of SV30 was optimized about 40% as the concentration of NaCl was 30 g/L. When the concentration of NaCl was 80 g/L and the feed 2-CP concentrations above 1000 mg/L, the removal rate could maintain at 98%, in which the SBR reactor achieved the best treatment effect. The concentration of extracellular polymers (EPS) of activated sludge reached to the highest amount of 142.6 mg/gSS at this operation condition. With the increase of salinity, the amount of polysaccharide in EPS also increased. The observation by using microscope and scanning electron microscopy (SEM) found that 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.