Process Water Recycling After Organics Removal at a Printing Paper Mill, 1999 Environmental Conference Proceedings

Tiina Riippa

Enso Publication Papers Oyj

Ville Elonen

Helsinki University of Technology

Raija Mattelmäki

Enso Research Center

Pertti Hynninen

Helsinki University of Technology

The objective of this study was to evaluate the possibilities to reuse treated process water in a printing paper mill water systems. A trial run with the paper machine clarified waters and waters from the TMP plant were carried out using a pilot-scale water treatment plant. The pilot unit consisted of biological treatment and different types of filtration units.

The reuse of treated TMP filtrate for pulp washing or retention aid dilution did not show any detrimental effects on pulp quality or on retention aid performance. Handsheets made with treated PM clear filtrate suffered slightly from brightness loss.

The possibilities to reuse treated water as a substitute for fresh water was limited by two parameters; the microbiological nature of the remaining suspended solids, and the color of the water. A tentative filtration and ozonation study showed promising results as a method to eliminate microbes in the waters. Microfiltration with a pore size of 0,5 mm removed all the suspended solids, but it had no affect on the color of the water. Ozone had biocidial effects and potential for reducing the color of the water.