November/December 1995
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November/December 1995 |
Imagine a paper mill that does not cause any water pollution at all. Plans to treat and recycle wastewater at Avenor's Thunder Bay newsprint mill in 1996 will bring the company closer to making this a reality.
The Thunder Bay complex, which consists of two pulp mills and a newsprint mill, was a pioneer in experimenting with effluent-free technology when the world's first "Rapson-Reeve" closed-cycle process was installed in one of its kraft pulp mills in 1977. Unfortunately, operational and pulp quality problems forced the mill to stop short of its goal of complete elimination of wastewater. Over the past few years, Avenor has been working with the Pulp and Paper Research Institute of Canada (Paprican) on the development of a new process to treat and recycle mill wastewater at the newsprint mill. This project is the first mill-scale development under a 1994 agreement between the federal government and Paprican to investigate the development of closed-loop technologies for pulp and paper mills.
The typical cycle of water use in a paper mill involves drawing water from a nearby lake or river, treating the water in a freshwater purification plant, using the purified water within the pulp mill, sending the effluent to an effluent treatment plant, and then discharging the treated effluent to a receiving water, usually the same river or lake that it was taken from. Although effluent is treated to meet strict federal and provincial standards, treated effluent does not usually have the appropriate chemical make-up for reuse in mill processes.
In the new treatment process planned for the Thunder Bay newsprint mill, effluent will pass through a combination of physical-chemical and biological treatment steps that will produce water clean enough to replace some of the water currently taken from the river, and eliminate some of the effluent discharges to the river. The physical-chemical component of the treatment process will involve sending the newsprint mill effluent to a clarifier where chemical additives will assist in the removal of colour, organic matter, solids and other contaminants. The effluent will then be biologically treated in the existing pure oxygen activated sludge system. This system uses microorganisms and oxygen to decompose the organic matter in the wastewater. After biological treatment, the water will be returned to the pulp and newsprint mills through the existing freshwater purification plants.
Pilot-plant trials were completed by Avenor and Paprican in the summer of 1994. Primary newsprint mill effluent from the full-scale primary clarifier was treated by the activated sludge process in the pilot plant. In the trials, the final effluent was combined in various proportions with surface water and purified using laboratory procedures simulating the mill feed-water treatments. The combined physical-chemical and biological treatments performed efficiently throughout the study.
With the pilot scale studies satisfactorily completed, the new process will be implemented in a step-by-step manner, starting in March 1996, when some of the treated newsprint effluent will be recycled instead of being discharged to the river. The recycled effluent will replace process water in the newsprint and pulp mills, thereby reducing the amount of fresh water needed from the river. The eventual goal is for all of the treated newsprint mill effluent to be recycled, making the Avenor Thunder Bay newsprint mill totally effluent free. Research is underway at Paprican to determine how the new process may affect pulp quality and the papermaking process. The speed at which complete recycling of the newsprint effluent is implemented will depend on the effect the new process has on mill operation and product quality.
If full implementation can be achieved, some benefits would include:
If this process is successful, it will result in a reduction of approximately 28 million cubic metres per year (7 billion gallons per year) in the quantity of effluent discharged to the Kaministiquia River. The system may eventually be applicable to most standard newsprint mills in the world.
For more information contact Rick McMullen, Manager of Technical and Environmental Services, Avenor Inc., 2001 Neebing Avenue, Thunder Bay, Ontario P7E 6S3. Telephone (807)475-2657.
Sommaire
Imaginez une fabrique de papier qui ne cause aucune pollution de l'eau. Grâce à ses plans de traitement et de recyclage des eaux usées produites par sa fabrique de papier journal, à Thunder Bay, dont la mise en oeuvre est prévue pour 1996, Avenor se rapproche d'autant de cet idéal.
Le complexe de Thunder Bay, soit deux fabriques de pâte et une de papier journal, a fait figure de pionnier en matière de technologies non productrices d'effluents lorsqu'on a installé pour la première fois au monde, en 1977, un procédé à circulation fermée, le «Rapson-Reeve» à la fabrique de pâte kraft. Toutefois, des problèmes d'ordre opérationnel et de qualité de la pâte ont empêché la fabrique d'atteindre son objectif d'élimination totale de ses eaux usées. Depuis quelques années, Avenor collabore avec l'Institut canadien de recherches sur les pâtes et papiers (Paprican) au développement d'un nouveau procédé de traitement et de recyclage des eaux usées produites à sa fabrique de papier journal. Il s'agit du premier projet à l'échelle d'une usine en vertu d'un accord passé en 1994 entre le gouvernement fédéral et Paprican pour étudier la mise au point des techniques en circulation fermée applicables dans les fabriques de pâte et papier.
Revised: March 14, 1997
Maintained by Kevin McGunagle,
mcgunaglek@ijc.wincom.net