Pure and Applied Chemistry

Abstract: Microbial community structures in sequencing batch reactors (SBRs) for azo dye wastewater treatment were analyzed by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). Effects of dye concentration and salinity were investigated for the decolorization of both reactive brilliant red K-2G and KE-3B. The results showed that the microbial community exhibited high color removal efficiency with high concentration of K‑2G (1100 mg/l) and moderate KE-3B (400 mg/l), respectively. Under high-salt conditions, decolorization of KE-3B was partially inhibited, while little effect was observed on decolorization of K-2G. The results of similarity analysis demonstrated that the DGGE banding patterns of microbial communities in K-2G and KE-3B decolorization systems were clustered into two independent groups. And it was suggested that the microbial diversities shifted proportionally with the decolorization rates for both dyes. The similarity index (Cs) of the bacterial communities under higher-salt conditions was more than those cultured with lower salinity. It was also found that microbial diversities turned out to be more abundant for both dyes with the increase of NaCl concentration. These results suggested that not only the stability but also the adequate dynamics and diversity of the microbial community structure are important for the stable performance of the SBRs treating hyper-salinity azo dye wastewater.