Because the increased environmental awareness and stringent legislation the paper and cellulose industry are forced to reduce their water consumption. Normally the wastewater from a paper plant is biologically treated, but the quality of the effluent may be good enough for disposal but it is not high enough for reuse as process water.
One method to clean the water is to use membrane filtration. The types of membrane filters that can be used are; Micro filtration (MF), Ultra filtration (UF) and Nano filtration (UF). There is some experience with a new type of membrane, the ceramic membrane. This membrane is used because it is easier to clean this filter with the backflushing principle compared to a carbon filter . Back flushing is a process in which the permeate flow is reversed periodically. This flow reversal in most cases improves the flux by removing some of the foulants from the membrane surface and pores.
The pH of the water is also important. At acidic pH lower fluxes and more fouling were observed compared to neutral pH.
|This can be explained by the lack of electro-static repulsion between the membrane and the solutes at acidic pH. At neutral pH electrostatic repulsion was established and thus the permeability was better maintained . |
Another technique that can be used is the membrane bioreactor (MBR). This technique is among other things used for the treatment of the wastewater from the bleach process. The treated water can be reused as process water .
 Niina Laitinen, Antero Luonsi, Erkki Levänen, Marianne Nyström, Effect of backflushing conditions on ultrafiltration of board industry wastewaters with ceramic membranes. Tampere, Finland 2001
 Jutta Nuortlla-Joklnen, Anne Kuparine, Marianne Nyström, Tailoring an economical membrane process for intemal purification in the paper industry. Lappeenranta, Finland, June 1998
 R. Tenno, H. Paulapuro, Removal of dissolved organic compounds from paper machine whitewater by membrane bioreactors: a comparative analysis. Espoo, Finland 1999
Information about water reuse in the food and beverage and textile industry,
Water disinfection and reuse in greenhouse horticulture
Information about water treatment and reuse of oily wastewater
Water reuse in the poultry industry
Find books about water recycling Should you know of any other interesting or more recent book, report, article or publication, concerning water reuse in paper industry please let us know, so that we can include reported case-studies in the above overview.