PT13 Aquatic Ecotoxicology I
Exhibit Hall
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(PT174) Toxicity Identification Evaluation of Nitrite in Food Processing Wastewater.

Baummer, J1, McCulloch, W1, Hammer, J2, Meyer, J2, Goodfellow, W1, 1 EA Enginnering Science and Technology, Sparks, MD2 Tyson Fresh Meats, Dakota City, NE

ABSTRACT- As part of a Toxicity Reduction Evaluation at a food processing facility, Phase I and Phase II Toxicity Identification Evaluations (TIEs) were implemented to identify the cause of acute toxicity to the water flea Ceriodaphnia dubia. Initially, the effluent was highly toxic with observed 48-hour LC50 values of <2.5 percent effluent and toxicity was also persistent. Results of EPA Phase I acute TIEs showed that none of the effluent treatments substantially reduced or eliminated acute toxicity. Routine ion scans revealed that the effluent had elevated concentrations of nitrite, a highly toxic nitrogen species to freshwater organisms. Results of toxicity tests also showed that invertebrates were far more sensitive to nitrite than vertebrate species (P. promelas). Because none of the standard EPA Phase I acute TIE treatments targeted nitrite, identifying and confirming nitrite toxicity was a challenge primarily because nitrite is rarely a constituent of effluents from treatment plants with biological nutrient reduction. Investigation of potential methods to reduce nitrite identified sulfamic acid agent, which effectively reduces nitrite nitrogen gas. When effluent was treated with sulfamic acid, effluent toxicity was substantially reduced. Subsequent synthetic effluent studies confirmed nitrite as the causative agent of toxicity to C. dubia.

Key words: toxicity identification, nitrite, Ceriodaphnia dubia, Pimephales promelas

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