Abstract: Bioremediation systems and methods are disclosed in which petroleum contaminated soil (PCS) are treated and recycled to below acceptable contaminant levels. The system comprises a treatment cell at a location removed from the original site of the contaminated soil and having a capacity to receive and treat PCS from numerous sources concurrently. The system includes a treatment water infiltration system and an air circulation system which, in combination, supply the required oxygen and nutrients to enhance the growth of naturally occurring, hydrocarbon-consuming microbial organisms as well as optimizing the hydrocarbon consuming activity of those organisms. The pH, system temperature, and growth inhibiting toxin concentration are all controlled in the systems and methods of the present invention to thereby further enhance microbial growth and hydrocarbon consumption.