Soils, contaminated with the explosive trinitrotoluene, can be remediated in a soil slurry process by adding easily degradable substrates. During the anaerobic fermentation of these substrates TNT is biologically reduced to metabolites, like triaminotoluene, which subsequently are immobilized in the soil by chemical reactions with soil components. Experimental investigations revealed that the cometabolic yield, defined as the ratio of TNT completely reduced per auxiliary substrate fermented, was not fixed but varied strongly with process conditions and could be increased by a factor of 10. Efforts to model this process were only partially successful as details of the underlying cometabolism are still unknown.