Contamination of an Unconfined Sand Aquifer by Waste Pulp Liquor: A Case Study |
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| Authors: | W D Robertson J F Barker Y LeBeau S Marcoux |
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| Institution: | Consulting Hydrogeologist, 383 Albert Street, Waterloo, Ontario, Canada, N2L 3V2.;Assistant Professor, Department of Earth Sciences, University of Waterloo, Waterloo, Ontario, Canada, N2L 3G2.;I.E.C. Beak Inc., 3333 boul. Cavendish, Suite 400, Montreal, Quebec, Canada, H3B 2M5.;CIP Inc., 1155 Metcalfe, Montreal, Quebec, Canada, H3B2X1. |
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| Abstract: | A zone of contaminated ground water has been identified in an unconfined sand aquifer adjacent to a pit into which spent pulp liquor was intermittently discharged from 1970 to 1979. A network of multilevel sampling, bundle-type piezometers was installed. Up to seven depthspecific sampling points were incorporated into each piezometer providing a cost-effective means for three-dimensional mapping of hydraulic head and water quality in the unconfined sand aquifer. Ground-water samples retrieved from this network showed an area of contamination 900 m long, 400 m wide, and more than 25 m deep. This plume is dispersed about the ground-water flow lines passing beneath the waste disposal pit, and it terminates at a vigorous ground-water discharge area located 800 m from the pit. The contaminated ground water is characterized by elevated concentrations of sodium (3,000 mg/1), chloride (590 mg/1), alkalinity (2,700 mg/1), total organic carbon (2,000 mg/1), chemical oxygen demand (10,800 mg/1), biological oxygen demand (2,000 mg/1), tannin and lignin (780 mg/1), and lower sulphate (1 mg/1) compared to background ground waters in the area. The apparent rate of sodium migration is more than 50 m/yr and is close to the average linear ground-water velocity. Removal of some organic matter by biological transformation has produced the increased alkalinity in the contaminated ground water and somewhat reduced pH. Tannin and lignin are relatively inert compared to other organic compounds found in the waste liquor. Extremely low sulphate levels occurring in the highly contaminated ground waters indicate the existence of conditions favorable for microbially-mediated sulphate reduction. |
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