This pilot plant study evaluated the pretreatment capabilities of a “Sessil” media for an undiluted high strength industrial wastewater (from a cellulose acetate manufacturing plant) over a ten-month period from May 1989. The Sessil media used consisted of 20 feet long 1.15 inch wide polyethylene strips hanging from wooden slats at the top of a 26 feet tall tower. The effects of organic and hydraulic loadings on the performance of the tower were examined. The characteristics of the influent wastewater on treatment performance were also determined. The wastewater, comprised mainly of waste acetic acid, some acetone, other organic solvents such as isopropyl alcohol, and some cellulose acetate fibers, had an average COD of 2300 mg/l, BOD of 1600 mg/l, influent suspended solids of 200 mg/l, SO₄ of 3000 mg/l, and an influent pH of 4.5, at an influent temperature of 40 C. The tower was found to consistently reduce the chemical oxygen demand (COD) of the wastewater even under adverse conditions as experienced during the shock loading phase when glacial acetic acid was added to the influent stream. During steady-state conditions, net total COD (TCOD) removals ranged from 28 to 52%, with an overall mean of 39%. For organic loads ranging from 164 to 374 lb TCOD/1000ft³day, the net removals (i.e. TCODinfluent-TCODeffluent) were between 81 to 104 lb TCOD, while biological removals (TCODinfluent-Soluble CODeffluent) ranged between 113 to 184 lb. COD removal was found to be an exponential function of the organic loading rate. The COD removals were not directly dependent on the hydraulic loadings, which ranged from 673 to 1738 gallons/day/ft². However, high hydraulic loading rates increased the rates of biomass sloughing and the variability of the tower effluent suspended solids (SS). The hydraulic retention time in the tower averaged 31 minutes and appeared insensitive to the hydraulic loading rates over the range studied. Volatile organic compounds did not appear to be a significant problem and there was insignificant volatilization of the compounds during its passage through the tower. Reductions in COD during volatilization tests were a result of biological stabilization. Tower influent organic constituents (viz. acids and alcohols) were reduced during passage through the tower. Acetic acid and acetone (the major components of the wastewater) were significantly reduced but incompletely removed. The other constituents (e.g. isopropyl and other alcohols) were more completely removed. Most of the removals appeared to have occurred in the upper one-third portion of the tower. / Master of Science