The principle mechanisms of solid-liquid separation processes are sedimentation and filtration, both including the formation and compression of a liquid-saturated bulk. The compressive properties of the bulk determine the operating parameters of solid-liquid separation devices and the achievable separation results. Information about the solids volume fraction of the bulk is essential for a better understanding of the physical mechanisms and precise modeling. A numerical model for the calculation of the local solids volume fraction during formation and compression of filter cakes and sediments was developed. The calculated results are compared with experimental NMR data.