Wastewater toxicity identification evaluations

After conducting the Phase I characterization tests, it is recommended that the investigator concentrates on the steps that are most clean-cut and have the major effect of reducing or eliminating the toxicity in the effluent. If toxicity in every effluent sample is not caused by the same toxicant(s), the characterization tests should indicate if the type of toxicant(s) is the same or different. Once identification is initiated, and suspect substances identified, the varying causes of toxicity can be evaluated because the concentrations of toxicants should correlate with the toxicity. 

Toxicity, and particularly chronic toxicity, must be present sufficiently frequently so that an adequate number of toxic samples can be obtained. Enough routine toxicity testing should be done on each effluent before a TIE is initiated to ensure that toxicity is consistently present. It is not important that the same amount of toxicity is present in each sample, rather the changing levels of toxicity can assist in determining the cause of toxicity. Also, once the acute toxicant is removed, it cannot be assumed that the sublethal toxicity that may occur is due to the same compound. 

Classes of chemicals characterized in Phase I include (1) volatile toxicants such as organic solvents (e.g. xylene, benzene) (2) particulate-associated toxicants present in sample suspended matter, which may become bioavailable to a 

Although Phase I of a TIE characterizes the types of toxicants suspected of being active in a sample, Phase II is designed to identify the specific toxicant(s) active. Methods for accomplishing this objective are described for freshwater samples in Durhan et al. (1993). Specific Phase II marine TIE methods are not available but Phase II of a marine TIE can be performed based on Durhan et al. (1993) methods. The procedures used to identify active toxicants characterized in Phase I are specifically designed to demonstrate the role of non-polar organic toxicants, ammonia, cationic metals, oxidants and filterable toxicants. 

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EVS Environment Consultants. (2001) Acute toxicity identification evaluations of Greater Vancouver Sewerage and Drainage District wastewater treatment plant effluents. Prepared for Greater Vancouver Regional District, 89 pp. 

Wells, M.J.M., Rossano, A.J.J. and Roberts, C. (1994) Textile wastewater effluent toxicity identification evaluation, Archives of Environmental Contamination and Toxicology 27, 555-560. 

Svenson, A., Sanden, B., Dalhammar, G., Remberger, M. and Kaj, L. (2000) Toxicity identification and evaluation of nitrification inhibitors in wastewaters, Environmental Toxicology 15 (5), 527-532. 

Another area of unmet need is in the identification of surfactants in textile wastewater. The effects of surfactants can be readily measured in terms of reduction of surface energy, foaming, aquatic toxicity, turbidity, and the like. However, it is often desirable to identify the exact concentration and identity of surfactants in wastewater. This is helpful, for example, in efforts to evaluate waste treatment system removal efficiency, or to reduce the detrimental effects of surfactants on the environment by pollution prevention (or cleaner production as it is called outside the USA). At present, there is no reasonable scheme for surfactant identification in textile wastewater. 

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