The dewatering system includes a first endless filter belt movable along its length through an upper run, then through an arc about a dewatering drum, and then through a lower return run in a sinuous path about a plurality of rollers. A flowable aqueous material or slurry, such as sludge, is deposited on the upper surface of the belt as it moves along its upper run. A subatmospheric pressure is applied to the lower surface of the upper run of the first belt to induce the liquid to drain from the sludge. A second endless filter belt is movable into sandwiched relationship with the first belt about the sludge and moves with the first belt about the dewatering drum and about the plurality of rollers in the sinuous path of the return run. One or more high tension endless belts are movable about the sandwiched first and second belts and material and some of the rollers in the return run, and tension is applied to the high tension belts to squeeze the first and second belts and the material as they move about the rollers in the sinuous path and to extract the liquid from the material.