• azo dye;
  • removal efficiency;
  • methane production;
  • anaerobic–aerobic sequential system


This study describes the treatment of azo dye Reactive Red 24 (RR 24) and methane production efficiency of anaerobic–aerobic sequential system. An upflow anaerobic sludge blanket and continuously stirred aerobic reactor were used to treat RR 24 dye. The effect of hydraulic retention time (HRT), organic loading rate, and sludge retention time ratio on the methane production percentage, color, and chemical oxygen demand (COD) removal was investigated. The sequential anaerobic–aerobic treatment of synthetic dye wastewater feed with 150 mg/L of RR 24 dye resulted in 100% color and 95.2% COD removal at 5.76-day HRT. The amount of methane produced in anaerobic reactor was 563 mL/day (80% methane intotal gas) and 129 mL/day (55%) for organic loading of 2.52 and 23.53 kg COD/(m3 day), respectively. © 2010 American Institute of Chemical Engineers Environ Prog, 2011