AbstractAs a result of manufacturing operations at the Durez Division of Occidental Chemical Corporation (OCC) located in North Tonawanda, New York, a highly phenolic wastestream is produced. At the time of this study, average phenols and total COD concentrations of the wastestream averaged 35,000 and 10,000 mg/L. Studies were conducted at the Durez Facility to assess sequenced anaerobic/aerobic biological activated carbon (BAC) process treatment of this wastestream. The first stage anaerobic BAC process achieved significant organic conversion with minimal solids production, and near stoichiometric methane production. Excellent polishing of the AnBAC process effluent was achieved in the aerobic BAC unit even under variable influent conditions. Effluent filterable COD from the aerobic BAC process averaged 165 mg/L and was speculated to be primarily non‐biodegradable soluble metabolic endproducts. Effluent phenols from the process typically were below 0.01 mg/L and averaged 0.04 mg/L. Overall process efficiency for total COD, filterable COD, and phenols were > 97, > 99, and approximately 100 percent, respectively.