| 摘要 |
<p>Waste waters in paper mills are clarified by flocculation and sedimentation, the sludge is passed through a centrifuge, e.g. a continuous worm centrifuge, and the overflow from the centrifuge is returned to the paper-making machine. Aluminium salts may be used as flocculating agents, and may be aided by an organic flocculating agent e.g. a polyacrylate. The pH of the sludge may be adjusted to above 9, e.g. by the addition of lime, before centrifuging, and the overflow brought back to a pH of 4.5 to 5, e.g. by the addition of sulphuric acid, before it is fed to the paper-making machine. Specification 804,330 is referred to.</p> |
