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The bitterant denatonium benzoate is being used in automotive coolants to deter human ingestion. The environmental impact of large scale use of bitterants has not been reported. Studies on the biodegradability of denatonium benzoate suggest that the benzoate is primarily responsible for the reported biodegradation. Since the aversive taste is associated with the denatonium ion, denatonium chloride was investigated in the Semi-Continuous Activated Sludge (SCAS) Test and the modified Sturm CO2 Production Test to determine if the denatonium ion would persist in the effluent after biological wastewater treatment. A microbial inhibition test demonstrated that the material is not toxic to the microorganisms in activated sludge between the concentrations of 1 and 150 mg active/L. The denatonium ion was not removed by microbial degradation or by adsorption onto the sludge solids in the SCAS test. The lack of CO2 production corroborated the lack of biodegradation observed in the SCAS test.

Automotive water pump seals which have failed prematurely during in-service use have been characterized using a variety of analytical methods. Nearly one hundred failed seals collected over the past several years from local automotive dealerships, major automotive manufacturers, coolant related fleet tests, and pump seal manufacturers have been examined as part of this study. This has enabled us to determine the chemical composition and morphology of surface deposits on failed seals and classify their failure mode. The main failure mode found for domestic in-service automobiles is filming, a term used to describe a failure type in which deposits form between the sealing surfaces resulting in a leak path. This paper reports on the composition, morphology and possible causes of in-service filming failures. In addition, the results of this study will be contrasted with those reported in other studies which found film transfer as the main type of failure.