The paper industry traditionally used water on a profligate scale. In recent decades the industry has responded to increasingly stringent environmental demands by various measures, one of the most cost-effective of which has been to reduce water consumption and consequential discharge. In fact, it has now become received wisdom among paper makers that reduced water consumption and reduced environmental impact go hand in hand. Reflecting this belief, regulatory authorities have increased the pressure upon the paper industry to reduce water discharges. Operation with Zero Liquid Effluent is now widely accepted as being best for the environment. The research reported in this thesis demonstrates that in mills making fine papers, this is not necessarily the case. In such mills, the minimal environment impact may well result from operating with a small, but non-zero, discharge of water, purified before final discharge to a watercourse. The reason lies in the nature of operation in fine paper mills. In such mills, grade changes take place very frequently, often several times each day on each machine. Each grade of fine paper is made from a furnish comprising a unique combination of raw materials, including special chemicals, dyes, and fillers. A portion of these materials fails to be retained during sheet forming. This portion remains in the backwater, in dissolved or suspended form, and is ultimately returned to the forming section. Backwater from one grade of paper cannot be used for another grade, because doing so would result in off-grade paper. During grade changes, therefore, the papermakers purge contaminants from the backwater system, by dumping contaminated backwater and by making off-grade paper, which must also be dumped. Both strategies result in brief shock loads on the environmental protection system.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:616898 |
| Date | January 2001 |
| Creators | Jones, John B. |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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