AN INVESTIGATION OF BIOLOGICAL INTERFERENCE IN WHOLE EFFLUENT TOXICITY TESTING OF A MUNICIPAL WASTEWATER

A two-year study was initiated to develop a strategy for addressing intermittent failures of chronic Whole Effluent Toxicity (WET) tests with Pimephales promelas, at the Riverview Wastewater Treatment Plant. The evaluation included a study of collection system water quality, plant performance, and a modified Toxicity Identification Evaluation (TIE). The collection system and plant were eliminated as vectors for the toxic agent. The modified TIE results raised the possibility of biological interference. This interference may have produced the periodic WET test failures. Adjustments were made to the sampling and TIE methodology to isolate the source and to identify the biological agent. A fungi was identified to the genus level, Tricophyton sp. and preliminary results supported the hypothesis that a pathogenic microorganism resided in algae growth within the plant effluent flume. The TIE provides an excellent tool for utilities for finding and identifying confounding factors in the WET testing.