The invention discloses an annular multi-stage
sedimentation tank for
sewage treatment. The annular multi-stage
sedimentation tank comprises an annular outer wall, a center column, five
settling tanks, a
sewage discharge channel gathering device and a
sludge guide
pipe; the center column is located in the center of the annular outer wall; the five
settling ponds are formed in the annular outer wall, distributed around the central column and separated by five partition plates; the
sewage discharge channel gathering device is of a spherical structure and is embedded in the bottom of the centralcolumn and the partition plates; the upper half part of the
sewage discharge channel collection device is separated by the partition plates and is respectively exposed in the
sedimentation tanks, a collection channel and five
branch channels are arranged in the
sewage discharge channel collection device, one end of each
branch channel is provided with a sewage inlet, and the sewage inlets of the
branch channels respectively correspond to the sedimentation tanks, so that
sludge at the bottom of the tank can be guided into the collection channel; the
sludge guide
pipe is provided with a sewage pump, and one end of the sludge guide
pipe is connected with the collecting channel. According to the invention, sludge at the bottoms of the five
settling tanks can be cleaned at the same time as longas the sewage pump on the sludge guide pipe is started, so that the operation is quite convenient.