It is important for the reduction of water consumption and conservation of energy to apply the closed system to the white water in papermaking process.
Generally coagulative sedimentation or floatation methods are applied to the whiter water as the primary treatment.
As the secondary treatment to the white water, a multi-media filter is installed to reduce the suspended solid in the water.
Our system consisting of the floatation and multi-media filter is in successful operation in our mill at Yufutsu.
The advantages are summarized as follow.
1) After filtering, the suspended solid contentment of the white water is 02 ppm and this filtered white water can be successfully used instead of fresh water.
2) By using our system, water consumption can be reduced by about 40 % on the conventional method.
3) It is estimated that energy conservation with our system is about 350 × 103 kcal/t of paper.
