Membrane technology for the future treatment of paper mill effluents: chances and challenges of further system closure.

The pressure on the European paper industry to further close its water circuits has increased significantly during the past decade. Since the technologies of the past can no longer meet the requirements of the future, new water treatment methods have become necessary. A constant rise in the interest in membrane technology expressed by the European paper industry confirms that in the future this method will evolve into a key technology for continued water savings. The publication provides an overview of current and future applications of membrane plants in the European paper industry. A range of technologies is briefly presented together with their advantages and drawbacks, and the economic potential of membrane use is discussed. Among other topics, the authors take a look at the utilization of membrane filtration for treating internal circulation water, partial flows containing coating colours, and biologically treated effluents. The technologies addressed include ultrafiltration, nanofiltration and membrane bioreactor technology. Possible recovery and treatment routes for the concentrates produced by the nanofiltration of biologically treated effluents are examined and evaluated.

Comparison of the endocrine effects of treated wastewaters from different paper mills by use of an in-vitro test with modified yeast cells.

As opposed to effluents from chemical pulp production, very little is known about the endocrine potential of papermaking effluents. To evaluate the endocrine potential of biologically treated effluents from the main grades produced in Germany (fine, graphic and packaging papers), 16 samples were studied by means of the Recombinant Yeast Estrogen Assay (R-YEA). 10 samples were tested positive; seven of them were effluents from recovered paper processing mills. Possible sources of endocrine disruptors in addition to wood components include papermaking chemicals, paper converting chemicals, if recovered paper is used, and/or detrimental substances introduced by impurities in these chemicals. Six of the above samples were subjected to individual substance analyses to detect endocrinologically active or potentially endocrinologically active substances. Even though phthalate compounds were detected in concentrations between 0.46 and 2.36 microg/L, only two of the six samples were tested positive in the R-YEA, because the test fails to adequately detect this compound's class. Despite this drawback, the R-YEA will be used for further studies because of the great variety of potential endocrine substances present in paper mill effluents. In particular, mechanical and recycled fibre pulps as well as the constituents of chemical additives must be investigated in more detail.