New Toxicity Tests at CARO: pH Stabilized Trout, High Hardness Daphnia & Sediments

Posted on January 18, 2014

Continuing the expansion of our toxicity capabilities, CARO is now accredited for pH-stabilization during the testing of acute lethality of wastewater effluent to rainbow trout. We have also developed testing with high hardness acclimated Daphnia, and sediment testing with chironomids and Hyalella. CARO has also developed testing for the presence of Klebsiella in pulp mill biosolids. These analyses are in addition to the other standard tests that we run in soil, water, air and other matrices (CARO Capabilities).

pH Stabilized Trout Testing
In many wastewater effluent samples, the CO2 content may be elevated as a result of high biological activity. Aeration of these samples, as required by the reference method for determining acute lethality of effluents to rainbow trout, may cause the pH to rise due to loss of CO2. pH stabilization replaces the CO2 lost due to aeration in order to maintain the pH throughout the test at the same levels found in the initial samples. Changes in wastewater pH during an acute lethality test may affect mortality if the toxicity of the substance is pH-dependent, as is the case with ammonia. Ammonia in the un-ionized form (NH3-N) is toxic to fish. The relative concentration of NH3-N rises with increases in pH. Depending on the initial pH of the wastewater and the magnitude of pH drift during testing, concentration of NH3-N that were below lethal levels at test initiation, could increase significantly during testing to cause rainbow trout mortality by the completion of the test. pH stabilized tests address the issue of residual ammonia toxicity in a wastewater effluent due to pH drift.

daphniaHigh Hardness Daphnia
Some clients have Daphnia analysis requirements in high hardness water. CARO has developed a method that tests Daphnia in high hardness samples, to better represent the analytical conditions present in our client’s samples.


Sediment Toxicity Testing
In the aquatic environment, sediment provides habitat for many organisms, and are also a major repository for chemicals that are introduced to surface waters. Sediment toxicity tests are cost-effective tools for determining whether contaminants are harmful to benthic organisms, as well as those frequenting the overlying water column. We have previously executed toxicity testing for oil spills and other contaminated sites using benthic invertebrates such as chironomids. Please discuss your next analytical project with a local toxicologist that can examine your needs and help you to determine what will work best for your project.

For certain applications, such as land application of pulp mill residues, identification of pathogenic organisms is required. Testing for E.Coli, Total and Fecal Coliforms, Enterococci and Salmonella are all within CARO’s current scope of testing, and they serve as an indicator of potential pathogens. These tests do not, however, identify specific pathogens of interest, such as Klebsiella. CARO has developed new methodology to identify Klebsiella, in direct response to client feedback and industry demand.

Please contact us if you require further information on this topic or would like to discuss using us for your toxicity testing. If you have any questions about CARO’s acute toxicity bioassay capabilities or other services offered by our laboratory please contact us here.


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