METHODS OF PURIFYING EFFLUENTS FROM THE MANUFACTURE AND BLEACHING OF WOOD PULP

摘要

1354455 Purifying waste waters from wood pulp treatment DEGREMONT SOC GENERALE D'EPURATION ET D'ASSAINISSEMENT 31 Oct 1972 [3 Nov 1971] 50166/72 Heading C1C Waste waters from wood pulp treatment are purified by adding aluminium sulphate so as to settle a portion of the non-biodegradable matter contained in the waters, the resulting solution being flocculated by the presence of excess aluminium sulphate with the pH of the solution adjusted to 5À4 by the addition of soda or lime. The settled and flocculated matters are separated and treated to recover the aluminium sulphate. The final solution may be further purified by treatment with activated carbon. The above method may be carried out in the system shown in Fig. 1 wherein waste waters are mixed with the sulphate in settling tank 2. Solid matter is removed in decanter 5. The resulting solution is flocculated in tank 8 by adding soda or lime from tank 9. The flocculated solution passes to decanter 11 and purified waters 13 exit the system. The settled and flocculated solids, 6 and 12, are mixed and then dehydrated in 17. The solids may be incinerated in 19, the resulting ash being treated with sulphuric acid to regenerate to aluminium sulphate.