Ultrafiltration and reuse opportunities of sectorial effluents from a kraft pulp mill in Brazil

The pulp industry is a high natural resources consumer and has a large polluting potential. The pulping sector with the most effluent generation is the bleaching plant. Based on the need of water consumption reduction, this research aimed to evaluate the treatment of the alkaline effluent from an EP-stage bleaching plant and the white water from drying machine using ultrafiltration membranes in order to enable the reuse of the permeate in the process. An ultrafiltration pilot plant was used. Laboratory analyses were performed for the feed, permeate and retentate. Flux and transmembrane pressure (TMP) data were obtained from the pilot plant database. There were an average color and COD removals of 38 % and 39 %, respectively, for the EP-effluent and 58 % and 67 %, respectively for the white water; and a high turbidity and TSS removal (above 98 %) for both effluents. Substantial metals removal such as sodium, potassium, calcium, iron, magnesium and manganese was achieved. Some possibilities to reuse were considered: return to the water treatment plant, cooling of the digester bottom, equipment cooling, reuse in evaporation surface condensers. The use of ultrafiltration for the treatment of the alkaline effluent from the bleaching EP-stage and white water can be an interesting option.