In this paper, the changes in biosolids’ rheological properties are used as a tool to assess dewaterability. A novel “immobilization cell” (IMC) is coupled with a dynamic mechanical rheometer to evaluate the effects of shear and normal forces as the filtration process occurs. We elaborate on the details of the instrument, method, application areas and how to achieve meaningful results. The shearing and normal force effects on biosolids dewaterability were determined. Increases in shear rates cause decreases in viscosity but slight increases in final solid content of samples. However, increasing the normal force was found to be the main parameter that governs the final solid content. The IMC offers a significant advance in allowing dynamic observation of biosolids dewatering while imposing both shear and normal forces during the filtration process.