Surplus biological sludge from wastewater treatment operations was converted into activated carbon and then added to the aerated vessel of an activated sludge process treating phenol and glucose. The addition of activated carbon, either sludge-based or commercial, enhanced phenol removal from 58 to 98.7% and from 87 to 93% for COD with feed concentrations of 100 mg phenol l(-1) and 2500 mg COD l(-1). No differences were found between the activated sludge-activated carbon bench scale continuous reactors operating with either commercial or sludge-based activated carbon in spite of the higher adsorption capacity of the former.