MP2 Toxicity of Mixtures
255 Portland Ballroom
1:20 PM - 4:40 PM, Monday
() Evaluation of causes of acute toxicity in Greater Vancouver (British Columbia) wastewater treatment plants.
Bailey, H1, Elphick, J1, Bertold, S2, 3, van Roodselaar, A2, 1 EVS Environment Consultants; presently with Nautilus Environmental, San Diego, CA, USA2 Greater Vancouver Regional District, Burnaby, BC, Canada3 Author to whom correspondence should be addressed
ABSTRACT- Effluent samples from four municipal wastewater treatment plants (WWTPs) were evaluated for acute toxicity using rainbow trout according to Environment Canada test protocols. Two plants discharging into marine waters provided primary treatment and two plants discharging into the lower Fraser River provided secondary treatment. A total of 75 samples were evaluated over the course of the study; the total number of samples tested for each plant ranged between 13 and 28. Samples were first screened for acute toxicity and samples that exhibited toxicity were then subjected to a variety of physical and chemical manipulations designed to characterize and confirm the causes of toxicity. Acute toxicity exhibited in samples from one of the primary WWTPs was due largely to anionic surfactants; ammonia also contributed to toxicity in some of these samples. In the second WWTP with primary treatment, mortality was largely caused by high BOD in the samples, resulting in oxygen depletion during the toxicity tests. Ammonia was determined to be the cause of acute toxicity at both secondary WWTPs; however, the observed toxicity in samples from these plants was largely due to increased pH caused by aerating the samples, resulting in a concomitant increase in the proportion of un-ionized ammonia present in the test containers. None of the causes of toxicity identified would be considered persistent in the receiving environment. This project was conducted at the EVS Environment Consultants laboratory under contract to the Greater Vancouver Regional District.
Key words: rainbow trout, toxicity identification evaluation, surfactants, ammonia