Anaerobic decolorization bacteria for the treatment of azo dye in a sequential anaerobic and aerobic membrane bioreactor

Textile dyeing wastewater is harmful to both marine organisms and human beings. This study focused on the treatment of wastewater containing an azo dye, Reactive Black 5 (RB5), using an anaerobic sequencing batch reactor (SBR) combined with an aerobic membrane bioreactor (aerobic MBR). In addition the anaerobic RB5 degrading bacteria were isolated and their individual performance were tested separately. Nearly 92.3 and 5.2% of COD removal and 74.6 and 9.1% of true color removal was achieved using the anaerobic SBR and the aerobic MBR respectively. Five types of high RB5 degrading bacteria isolated were sequenced to be different subspecies of Lactococcus lactis, which could degrade more than 99% of the RB5 within 5.5 h. Twenty types of medium RB5 degrading isolation were observed to be different subspecies of Lactobacillus casei, which could degrade more than 99% of the RB5 within 36 h. Finally, the experiments also showed that the RB5 degradation performance of the L. casei was improved by the suitable addition of carbon and nitrogen source in the medium.