Le recyclage de l'eau dans la papeterie

Recycling of water in paper mills

Ingénieur I.N.S.C.I.R., Agence Financière de Bassin Rhin-Meuse

Abstract

It can be considered a general rule that the first step towards effective pollution control in factories is to redesign the water circuits. Paper mills are a striking example of this, as circuit modifications usually result in more efficient use of raw materials and rationalized production. Fifteen pollution control policies now being implemented in the Rhine-Meuse river valleys are based on action to be carried out in two phases. The first phase is to consist in redesigning the water supply and sewer systems with a view to maximal recycling. In the second phase, non-recycled water will be purified at an appropriate station. In some cases, especially board mills, the purification plant will also be acting as the overall pulp recovery unit for the mills. The sludge is returned to the pulper, whilst the water is generally processed and recycled for further use in the factory. The Béghin Company's Kaysersberg board mills for example, which produce 200 metric tons of cardboard from waste paper daily, used to consume sorne 620 m3 of water hourly in 1972. The waste water passed through a settling tank and then discharged into a river. When the settling tank was operating properly, the residual load was 50 mg/l suspended matter and 150 mg/l COD. Breakdowns were frequent. The following comprehensive programme has since been put into effect with the regional finance authority's assistance :- Improvement of the settling and flocculation tank ; - Recycling of sludge (a daily raw material saving of 15 metric tons) ; - Recycling of white water ; -Recycling of clear water after passing through a sand filler and chlorination. The following results have been obtained to date : [See table in PDF file]. Further improvements are expected. At the final stage, total bleed discharge should not exceed 9 m3 of water per metric ton produced.