In response to this concern, computer models, such as Toxchem, have been developed to predict the mass of the VOCs in the wastewater treated by biotransformation and the mass stripped to the atmosphere and released in the treated effluent. [...] The dissolved oxygen concentration in the bio-reactor is controlled by the pressure of the oxygen supply. [...] Since there is no potential for volatilization, the biotransformation rate for the VOCs is calculated by the rate of decline of the concentration of the VOCs in the bio-reactor. [...] The effects of varying the wastewater COD concentration and the dissolved oxygen concentration were examined in the aerobic environment. [...] The less halogenated the compound, the faster the rate of oxidation.