PARENT SESSION

2A - Mixture toxicity
Poster Hall
8:30 AM - Monday, 28 April 2003
Chair: Hermens, J.¹, ¹
Co-chair: Toy, R.², Backhaus, T.³, ^{2 3}

(MOP/81) Hazard identification of pulp mill solid waste to aquatic species.

Hawkins, Stephanie¹, Hedley, Carolyn¹, Orr, Heather¹, van den Heuval, Mike², Hodson, Peter¹, ¹ Queen's University, Kingston, Ontario, Canada² Forest Research, Rotorua, North Island, New Zealand

ABSTRACT- The use of pulp mill biosolids as a soil amendment on agricultural and silvicultural land is an increasingly prevalent practice. The potential risks of biosolids to aquatic biota may vary with treatment process, wood furnish, and phase of treatment. We sampled the final combined biosolids from thermomechanical (TMP) and bleached kraft (BKM) pulp mills using activated sludge treatment systems, and separate primary and secondary biosolids from an aerated stabilization basin (ASB) system treating the combined effluent of TMP and BKM mills (TMP/BKM). Acute median lethal concentrations (LC50s) were 0.56, 6.4, >18, and >10 g dw/L for TMP, BKM, TMP/BKM primary, and TMP/BKM secondary biosolids respectively. TMP biosolid lethality may have resulted from high resin acid concentrations (83 mg/g dw). CYP1A induction was observed in the TMP/BKM secondary exposures, the only samples with appreciable concentrations of the polycyclic aromatic hydrocarbon retene. Chronic testing with early life stages (ELS) of trout yielded LC50s of 0.26, >10, and >10 for TMP, BKM, and TMP/BKM primary solids respectively. Mortality in TMP/BKM secondary exposures was in part dependant on the degree of physical interaction with the material, and ranged from <1.0 to >1.8 g dw/L. Signs of sub-lethal ELS toxicity included craniofacial malformations, hemorrhaging, and edemas; these were observed only in samples with high resin acid or retene concentrations. Exposures of ELS to pure dehydroabietic acid or retene indicated that the signs of sub-lethal toxicity were consistent between the pure compound and biosolid exposures. Our findings suggest that effluent constituents are not entirely mineralized during treatment, but persist or are biotransformed and continue to pose a toxicity hazard to aquatic species.

Key words: Biosolids, Wood extractives, Biotransformation, Rainbow trout