New Zealand Journal of Marine and Freshwater Research abstracts

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Panel tests for evaluating the appearance and odour of the lower Tarawera River

R. J. WILCOCK
R. J. DAVIES-COLLEY

Water Quality Centre
Ministry of Works and Development
Private Bag, Hamilton
New Zealand

Abstract Kraft pulp mill effluent in a continuous discharge both discolours and imparts an offensive odour to lower Tarawera River water. Panel tests were carried out to evaluate threshold detection levels (TDLs) for odour and colour. A 50% TDL of c. 4 Hazen colour units (0.5% effluent to river V/V) was estimated for an increase in Kraft loading above zero. A 95% reduction in the present level of Kraft effluent discharge would be required before the Kraft colour would no longer be noticeable by comparison with up stream river water; a large reduction would be needed before the public would even notice an improvement in water appearance. Panel studies established that odours did emanate from the river, and that the 50% TDL for effluent in river water was 1% (V/V). In the field a "pulp and paper" smell was noticeable at an effluent to river water ratio of 2%. Tasman mill effluent would need to be reduced by 90% at mean annual or lower river flows in order to reduce river effluent concentration to 1%. A major reduction in Kraft effluent loading would be necessary if the Tarawera River is to be suitable for uses other than waste disposal.

Keywords Tarawera River; odour; colour; appearance; panel tests; threshold detection limit; Kraft effluent; conspicuous; objectionable

New Zealand Journal of Marine and Freshwater Research, 1986, 699-708Received 24 November 1985; accepted 14 April 1986

PDF file of entire paper: medium quality (724K); (scanned from paper original: notes about this process)

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