Abstract: A water treatment system is provided with a fluidized bed reaction vessel having a water inlet and a water outlet, the reaction vessel having a region of continuously varying cross-sectional area intermediate of the water inlet and the water outlet. The continuously varying cross-sectional area intermediate of the water inlet and the water outlet of the reaction vessel is configured as a substantially truncated conical internal surface. A region of substantially constant cross-sectional area intermediate of the water inlet and the water outlet, the region of substantially constant cross-sectional area is coaxially disposed in relation to the region of continuously varying cross-sectional area. The region of substantially constant cross-sectional area comprises a substantially cylindrical internal surface. Also, the region of substantially constant cross-sectional area is axially adjacent to a region of diminished cross-sectional area of the region of continuously varying cross-sectional area.