NOVELTY - The sewage disposal system has water storage tank (1) for storing wastewater containing suspended solid, flocculation tank (2), solid-liquid separator (10), storage tank (16) and filter apparatus (20). The filter apparatus removes suspension microparticles remained in supernatant liquid produced by separator (10). Filter apparatus has filter units (20A-20C) sequentially connected with storage tank by pipeline, and filtration degree of supernatant liquid discharged from storage tank is gradually decreased in order, when passed through filter units.    USE - For purifying wastewater, such as factory drainage wastewater, underground contaminated wastewater and water flowing out of contaminated soil.    ADVANTAGE - The sewage disposal system efficiently enables the purification of wastewater. The suspended solids are efficiently removed from wastewater. The filter apparatus has improved filtration ability. The clogging of filter medium by microparticles of iron and nickel is prevented.    DETAILED DESCRIPTION - The sewage disposal system has a water storage tank (1) for storing wastewater containing suspended solid, a flocculation tank (2), a solid-liquid separator (10), a storage tank (16) and a filter apparatus (20). The tank (2) carries out addition of flocculant to wastewater discharged from tank (1), and aggregation of suspended soil. The solid-liquid separator centrifuges suspended solid ejected from tank (2). The tank (16) recovers supernatant liquid obtained by separation removal of aggregate of suspended soil in separator (10). The filter apparatus removes the suspension microparticles remained in supernatant liquid. The filter apparatus has at least 3 filter units (20A-20C) having filter medium in casing. The filter units are sequentially connected with storage tank by pipeline, and filtration degree of supernatant liquid discharged from storage tank is gradually decreased in order, when passed through filter units.    DESCRIPTION OF DRAWING(S) - The figure shows the systematic diagram of sewage disposal system. (Drawing includes non-English language text)    Water storage tank (1)    Flocculation tank (2)    Solid-liquid separator (10)    Storage tank (16)    Filter apparatus (20)    Filter units (20A-20C)