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Whole Effluent Testing (WET) Toxicity in Wastewater: Methods, Approaches and Interpretation of Test Results

Whole Effluent Testing (WET) Toxicity in Wastewater: Methods, Approaches and Interpretation of Test Results (1)

Tuesday, May 14, 2019 - 1:30 P.M. EDT

About This Webinar:

Wastewater dischargers operate under National Pollutant Discharge Elimination System (NPDES) permits, based on the federal Clean Water Act (CWA), and must adhere to a complex array of regulations that include evaluating and eliminating any persistent effluent toxicity.

Whole Effluent Toxicity (WET) testing is used to determine if a treated wastewater discharge into receiving waters poses a potential risk of toxicity to aquatic organisms and human health. WET tests describe the aggregate toxic effect of an effluent sample measured by a test organism's response to exposure (e.g., lethality, impaired growth, or reproduction). WET monitoring requirements are included in NPDES permits to determine whether a wastewater has a reasonable potential to cause acute (i.e. lethal) and/or chronic (i.e. sub-lethal effects) toxicity in aquatic organisms. 

WET test methods include procedures for freshwater, marine, and estuarine test species. Freshwater organisms used in testing include invertebrate (water flea), vertebrate (fathead minnow), and a plant (algae) to identify the most sensitive species and any potential for toxicity. For saltwater/esturine testing, an invertebrate (mysid shrimp), vertebrate (sheepshead minnow or menidia), and a plant (giant kelp) are used..

This webinar will include examples of how to interpret toxicity test results, and how to narrow down and identify potential toxicants.

Ten Things to Know about Bioassay Sampling and Testing:

  1. Use pre-cleaned containers and auto-sampler tubing. 
  2. If using bleach to clean tubing/containers, make sure to rinse very thoroughly as bleach causes toxicity at very low levels.
  3. Make sure to ice samples while collecting. EPA requires the temperature to be at or below 6oC when it arrives at lab.
  4. Dual-end point tests (acute derived from chronic tests) can be a cost saver – but with elevated ammonia in effluent, conduct separate acute tests as temperature is lower and ammonia is less toxic.
  5. If lab detects chlorine in sample, and no toxicity is observed possible interference may be occurring.
  6. If toxicity is observed in first 24 hours of test, look for obvious toxicants such as chlorine, ammonia.  
  7. Chlorine toxicity is much lower for water flea than fish.
  8. Ammonia toxicity is much lower for fish than water flea.
  9. If there is an interrupted dose response in the toxicity test results, call the lab and ask them to explain results prior to submitting to regulatory agency.
  10. If the test results look odd then ask the lab to determine if the results can be explained as anomalous.

 A question and answer session will immediately follow the presentation. At the conclusion of each webinar, you will be asked for your feedback and opinions for future webinar topics to be developed by TestAmerica.

May 14, 2019


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PDH Credit:

All webinar attendees will receive a certificate of attendance with PDH Credit issued by TestAmerica. Certificates will be emailed two days following the presentation. Contact your state to determine whether these credits meet the guidelines set forth by your state's board.

The Presenters:

Brett Muckey

Aquatic Toxicology

Department Manager, Eurofins TestAmerica


To view a recorded version of this webinar, please contact patricia.mcisaac@testamericainc.com.