Whole Effluent Toxicity (WET) refers to the aggregate effect to aquatic organisms from all pollutants contained in a facility’s wastewater. WET tests measure wastewater’s effect on specific test organisms’ ability to survive, grow, and reproduce. The WET test methodology consists of exposing living organisms, such as water fleas (Ceriodaphnia dubia) and fathead minnows (Pimephales promelas) to various concentrations of a sample facility’s wastewater effluent stream. WET test results are used by National Pollutant Discharge Elimination System (NPDES) permitting authorities to determine whether a facility’s permit will need to include specific WET-related requirements. The U.S. Environmental Protection Agency (EPA) and various state permitting authorities have required some airports to conduct WET testing of stormwater runoff from portions of the airport where pavement and aircraft deicing occurs to determine if additional sampling or corrective actions will be required. However, due to the episodic nature of airport stormwater deicing discharges, the potential for multiple discharge locations, variations in the size and flow of receiving water bodies, the exposure of organisms to varying deicing concentrations, the effect of seasonality, and other issues, WET testing at airports faces unique challenges. Research was needed to produce guidance on how to appropriately conduct and apply WET testing for evaluating the effects of airport stormwater deicing discharges.
The objectives of this research were to: (1) describe how WET testing is used at airports for monitoring stormwater deicing discharges, including WET testing strengths and weaknesses; (2) evaluate whether current WET sampling protocols accurately reflect the toxicity of episodic airport stormwater discharges containing deicing fluids; (3) develop approaches for accurately applying the results of laboratory WET testing of episodic airport stormwater discharges containing deicing fluids to determine if in situ water quality impacts are occurring or will occur; and (4) provide guidance on the use of WET testing at airports for stormwater deicing discharges.