Methods for biodegrading nitroaromatic compounds present as contaminants in soil or water using microorganisms are disclosed. Water is treatable directly; dry soil is first converted into a fluid medium by addition of water. The preferred method comprises two stages, each employing microorganisms: a fermentative stage, followed by an anaerobic stage. The fermentative stage is rapid, wherein an inoculum of aerobic and/or facultative microorganisms ferments a carbohydrate added to the fluid medium, exhausting the oxygen in the fluid medium and thereby inhibiting oxidative polymerization of amino by-products of the nitroaromatics. In the subsequent anaerobic stage, an inoculum of a mixed population of anaerobic microorganisms completes the mineralization of the contaminant nitroaromatics, using the remaining carbohydrate as a carbon and energy source. Preferably, the carbohydrate is a starch and the aerobic and/or facultative microorganisms are amylolytic, which cleave the starch at a moderate rate throughout both stages, ensuring a sustained supply of metabolizable carbohydrate. The microorganisms are preferably selected to be resistant to the types and concentrations of nitroaromatics present as contaminants.