Decolorization of azo-reactive dye by polyphosphate- and glycogen-accumulating organisms in an anaerobic–aerobic sequencing batch reactor

An anaerobic–aerobic sequencing batch reactor with a sludge age of 8 days and anaerobic+aerobic+settling times of 18+5+1 h, was used to decolorize an azo-reactive dye wastewater. The nutrient broth (NB) and sodium acetate (SA) solution at 500+0, 350+150, 250+250 and 0+500 mg/l as COD was fed to the system to promote the polyphosphate-accumulating organisms (PAOs), while only glucose (500 mg/l COD) was used as a glycogen-accumulating organisms (GAOs) promoting substrate. The decolorization capability of the process was about 73–77 and 59–64% in terms of ADMI for the systems which the PAOs and GAOs proliferated, respectively. The color reduction was mainly achieved within the first 2 h of the anaerobic stage.