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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.

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The objective of this study was to evaluate the closing of the water circuit and reusing the treated effluent in the production of TMP, using simulations performed with the Aspen Plus®. The treated effluent was reused to replace 50, 75 and 100% of the well water. An adaptation of the Aspen Plus® program simulating the TMP production process and a dynamic simulation test to verify the accumulation of non-process elements (NPEs) in industrial processes at different proportions of reuse were evaluated. The quality of the final product was assessed in laboratory bleaching tests for pulp brightness and brightness reversion. The concentrations of the NPE were 0.00097, 0.00122 and 0.00145 kmol/h for Mn2+, 0.012929, 0.018368 and 0.023595 kmol/h for Fe3+ and 0.000542, 0.000722 and 0.000948 kmol/h for Cu2+, with the recycling of the treated effluent of 50, 75 and 100%, respectively. The brightness and brightness reversion of the pulp were similar with the different proportions of effluent reuse and with the use of fresh industrial water, with values ranging from 83.37 to 83.97% ISO and 5.43 to 6.38 ISO units, respectively. The use of treated effluent did not affect the pulp quality, which could diminish the water use in a pulp mill.