Weighted sedimentation

The mixture of raw water and coagulant-flocculant flows into the bottom of the sedimentation tank, where it encounters microsand that sticks to the floc, increasing its weight. The floc then sinks to the bottom of the tank. The settled water is run off at the top of the tank but first has to pass through sloping lamella units which force the lightest particles, swept along by the upward flow of the water, to settle.

The sludge is pumped out of the bottom of the sedimentation tank continuously and is sent to a hydrocyclone where the sludge is separated from the microsand by centrifugal force. The sand is re-injected into the sedimentation tank; the sludge is sent to the sludge treatment unit.