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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
[1]. 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
[2].
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 [3].
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[1]
Niina Laitinen, Antero Luonsi, Erkki Levänen, Marianne Nyström,
Effect of backflushing conditions on ultrafiltration of board industry
wastewaters with ceramic membranes. Tampere, Finland 2001
[2] Jutta Nuortlla-Joklnen, Anne Kuparine, Marianne Nyström,
Tailoring an economical membrane process for intemal purification in the
paper industry. Lappeenranta, Finland, June 1998
[3] 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.
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