Method and device for purifying domestic sewage

The invention provides a method and device for purifying domestic sewage. The method includes the steps that the to-be-treated sewage flows through more than two stages of earthworm biofilters, and supernatant obtained after the sewage is precipitated is purified water. The device comprises a water distributor, a purification part and a precipitation part, wherein the water distributor, the purification part and the precipitation part are sequentially arranged in the flowing direction of the to-be-treated sewage. The purification part comprises the at least two stages of earthworm biofilters, the earthworm biofilters are filled with spherical ceramsite filler, eisenia fetida is inoculated, and biological film microorganisms can grow on the spherical ceramsite filler. Due to the fact that earthworms and the biological film microorganisms are contained in the earthworm biofilters at the same time, the activity of biological films can be improved and the blockage problem can be solved through stirring of the biological films by the earthworms in the biofilters, intercepted organic pollutants can be continuously degraded by the microorganisms, the earthworms and the microorganisms achieve the synergistic effect on purification of the to-be-treated sewage accordingly, the sewage can be more efficiently purified, and recycled purified water can be obtained.