Methods and systems are provided for two-stage treatment of contaminated particulate material, such as soil, sediment, and/or sludge. The methods and systems utilize a thermal desorption process combined with a smoldering combustion process. The contaminated particulate material is first exposed to thermal desorption at high temperatures (e.g., greater than 150° C.) to form a heated contaminated particulate material. Next, a smoldering combustion process is initiated by introducing a combustion-supporting gas. The combined process can take place in the same or different treatment units. Treating the particulate material with a thermal desorption process prior to a smoldering combustion process enhances the completeness and throughput compared to operating these processes separately.