decolourisations and biodegradations of model azo dye solutions using a sequence batch reactor, followed by ultrafi ltration

the main objective of this study was to investigate the effi ciency of biological treatmentof azo dye-containing wastewater with a sequencing batch reactor system, followed by ultrafi ltration.the performance of the system was quantifi ed by measuring the chemical oxygen demand and azo dyeconcentration. the biodegradation was carried out under combined alternating anaerobic and aerobicconditions with nylosan yellow e2rl sgr as a model azo dye contaminant. the bioprocess revealed amaximal reduction of chemical oxygen demand and dye removal effi ciency of 91% and 85%, respectively.after ultrafi ltration of effl uent from the biological treatment, the effi ciency increased to 94% for chemicaloxygen demand and to 97% for the azo dye decolourisation. samples of activated sludge from the bioprocesswere collected for microbial characterisation. bacteria and fungi were isolated and identifi ed by 16s rrnagene and its1-5.8s rdna-its2 sequence analysis, respectively. serratia marcescens and klebsiellaoxytoca were the most common bacteria with the highest number present during the aerobic and anaerobicphases of the bioprocess. in addition, a high number of elizabethkingia miricola, morganella morganii,comamonas testosterone, trichosporon sp. and galactomyces sp. were detected. taken together, ourresults demonstrated that the sequencing batch reactor system combined with ultrafi ltration is an effi cienttechnique for treatment of wastewater containing azo dye. moreover, the ultrafi ltration effectively removesthe microbiota from the fi nal effl uent resulting in stable product water.