Performance of a pilot scale Hybrid Vertical Anaerobic Biofilm (HyVAB) reactor treating petrochemical refinery wastewater is presented here. The reactor is an integration of a bottom anaerobic sludge bed and a top aerobic biofilm stage and was operated continuously for 92 days at 21 ± 2 °C. Wastewater was fed continuously to the reactor with step flow increases reducing hydraulic retention time from 55 to 12 hours, increasing organic loading rate from 3 to 33 kg-COD/m3·d. The HyVAB removed on average 91% and 86% of the soluble and total feed COD, respectively, at steady state and loads up to 23 kg-COD/m3·d, of which 98% of the soluble COD removal occurred in the anaerobic stage. Methane yield ranged from 0.29 to 0.51 L/g-COD removed, including conversion of settled aerobic sludge to methane. Sludge production was low (0.04 kg-VSS/kg-COD removed) and biogas methane content high (84 ± 2%). The results demonstrated that HyVAB is an efficient, low footprint alternative for high strength wastewater treatment.

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