Land treatment technology has been extensively used for the disposal of petroleum hydrocarbon containing wastes. Effective management of land treatment systems requires optimum design and operation of the system in order to achieve the fastest and most complete degradation of petroleum hydrocarbons without contamination of the environment. This paper describes a model that can be used for optimal design and operation of land treatment systems for petroleum hydrocarbon containing wastes. The model is composed of system simulator and optimization submodels. Selected model applications are presented to demonstrate the applicability and utility of the model. Such model applications include determination of the optimal design and operation conditions for the land treatment of petroleum hydrocarbon containing wastes under various different site and soil environmental conditions and practical waste disposal scenarios.