An integrated anaerobic-aerobic bioreactor (IAAB) for the treatment of palm oil mill effluent (POME): Start-up and steady state performance

► We present a new bioreactor design-integrated anaerobic-aerobic bioreactor (IAAB). ► The start-up and steady state condition of IAAB were accomplished in 45 days. ► The hollow centered packed bed minimized the operational problems. ► More than 99% BOD removal efficiencies at OLR of 10.5 g COD/L day were achieved. ► The treated effluent quality complied with the discharge limit (<100 mg/L).