What is a bioassay?

Pace Analytical Bioassy Scientist testing pitri dish, WET Testing, aquatic toxicityA bioassay is the measurement of the concentration or potency of a substance by its effect on living cells or tissues.  This test determines the relative strength of a substance by comparing its effect on a test organism with that of a standard preparation. For environmental testing, bioassays provide an integrated picture of overall toxicity of an effluent or a sample of water, sediment, or soil from a contaminated site.

Why Bioassay Testing is Important

Testing for Environmental Microbiology and Aquatic Toxicity requires experienced and skilled personnel when dealing with various organisms to meet regulatory discharge requirements to ensure the safety and quality of water sources in the natural habitats.

In 1972, as part of the U.S. Clean Water Act, the NPDES permit system was created to regulate sources of pollution – the act states that there shall be “no discharge of toxic substances in toxic amounts”. These toxic substances can range from polymers used in wastewater treatment processes to heavy metals that flake off brake pads and are deposited on our roads.

Whole Effluent Toxicity (WET) refers to the aggregate toxic effect to aquatic organisms from all pollutants contained in a facility’s wastewater (effluent). WET testing is a critical component of monitoring the health of aquatic ecosystems and it is included in many National Pollutant Discharge Elimination System (NPDES) permits. WET tests measure wastewater’s effects on specific test organisms’ ability to survive, grow and reproduce.

The test organisms are exposed to the sample and a laboratory control, and the biological responses are compared. When testing, however, there are two main types of bioassays – acute and chronic:

  • Acute tests are shorter in duration and measure mortality.
  • Chronic tests are longer in duration (typically lasting 7 days), and measure mortality as well as a sub-lethal endpoint like growth or reproduction.

WET Test Planning

Crucial to WET test planning is reviewing your NPDES permit because it includes a detailed description of your WET testing requirements. This section should include: the type of test required (acute vs chronic), the testing frequency, the approved test species, the permit limitations (Toxic Unit or Pass/Fail), and what to do if there is an exceedance.

Pace® understands that NPDES permits can be complicated, especially with new biomonitoring requirements. We simplify biomonitoring requirements for our clients by providing services such as:

  • Interpretation of NPDES permits
  • Test scheduling
  • Quarterly testing Reports formatted specifically for your state agency
  • Quality assurance documentation
  • Reference toxicant control charts
  • Sample collection kits
  • Sampling services

Pace® WET Testing Services

Pace® is at the forefront of WET testing. The highly experienced Pace® scientific staff performs testing on products, pure chemicals, process wastes, storm water and effluent discharges utilizing the latest instrumentation in state-of-the-art aquatic toxicology laboratories.