This paper briefly summarizes work undertaken on a pilot plant study of the biofiltration process for the City of Tucson at the Roger Road Wastewater Treatment Plant (WWTP). Engineering services related to the investigation were performed during the period from December, 1975, to August, 1976. Assistance provided by engineering staff of the City of Tucson Department of Water and Sewers and the staff at the Roger Road WWTP is gratefully acknowledged.