SOUTH DAKOTA Department of
Environment & Natural Resources

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Pierre, SD 57501
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Surface Water

Whole Effluent Toxicity Testing

Whole Effluent Toxicity (WET) testing uses fathead minnows and Ceriodaphnia dubia to measure if a discharge is or may be toxic.

Fathead Minnow
Pimephales Promelas

Ceriodaphnia dubia

The test can be either acute or chronic. Acute tests are short-term tests, usually 96 hours or less. The acute test determines if the effluent would be lethal to aquatic life and measures whether the fathead minnows and Ceriodaphnia live or die.

Chronic tests are longer term tests. The test is typically run for seven days or less. The fathead minnow test measures whether the discharge effects the growth rate of the minnow. The Ceriodaphnia dubia test measures whether the discharge effects the reproduction of the Ceriodaphnia. The chronic test also measures if the effluent would be lethal to aquatic life.

The testing protocols have strict test conditions that include a constant temperature, specific light quality and intensity, dissolved oxygen requirements, etc. The Environmental Protection Agency has provided detailed information on the whole effluent toxicity test methods at their web site. 

For more information about South Dakota's whole effluent toxicity requirements, please contact Tim Flor with the Surface Water Quality Program at (605) 773-3351.