PURPOSE: To make sure falling down of a sludge into a pit of sedimentation basin at the lower side without causing whirl-up of the sludge, in a multi-stage sedimentation basin by raking the sludge deposited in a sedimention basin at the upper stage to the pit side.
CONSTITUTION: In a multi-stage sedimentation basin 1 constituted of an upper side basin 1a and a lower side basin 1b; a basin bed 2 is installed between both basins 1a, 1b with its one end common to both basins 1a, 1b, and a sludge pit 3 is installed at the lower side of the basin 1. Raw water flows in from an inlet port 7a having a gate 8, and after the sludege is settled, dirty water flows out of the basin 1 from an overflow weir 6. The sludge deposite in the sediumntation basin of each stage is racked by sludge raking machines 4a, 4b to the side of the sludge pit 3. A subraking machine 9 is provided to the inflow-side end of the basin except the lowest stage-basin to rake up the sludge raked by the main sludge raking machines to the side or the center of the basin, and the sludge is made to fall into the pit 3 by a tubular falling-sludge guide 10 which prevents the sludge from flowing into the lower basin again.
MATSUMOTO GUNJI
FUKUOKA TOSHIROU
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