At Aster Bio, we receive many samples from new processes that may impact the existing wastewater unit biomass. We wanted to develop a rapid test for screening purposes that could identify percent inhibition to standard wastewater organisms. In many instances, you use a spiked oxygen uptake rate (OUR) or perform a respirometery study to see if microbial respiration is inhibited by the compound.
Background information on the Tox-Bac test
While we have used OUR to test biomass respiration as an indicator of high loadings or other biomass stress, we found the spiked OUR subject to variation from the MLSS sample and often the lack of fresh MLSS when doing extensive lab toxicity testing.
Key to our needs was a reproducible biomass for consistent inhibition reporting results. So, our R&D group developed a known preserved biomass from various vegetative microbes. The resulting preserved biomass was similar to that found in municipal and light industrial wastewaters. This "known" biomass contains a uniform mix of microbes that gives a narrow range of oxygen uptake when hydrated on chlorine free or DI water. The DI water respiration rate serves as the control as it has no inhibition to the microbes. The test influent is evaluated at pre-set dilutions for determining toxicity.
We also designed the test for use with existing BOD bottles & DO meters - so the test could be run in any standard wastewater facility without needed any unusual equipment or reagents. The resulting test takes approximately 25 minutes per sample with most of the time being inactive as the microbial respiration is measured only between minutes 19 and 21 (near maximum activity is reached and no reproduction has occurred).
Example Application using Tox-Bac™
A customer was introducing a new process unit that was going to add a completely new influent to the wastewater treatment system. The environmental staff wanted to know the potential impact from the new influent on the biomass. The waste stream was adjusted to a pH of 7.2 for purposes of testing and allowed to aerate for 1 hour to ensure oxygen saturation. The test was performed using a DI water control with the influent being added at 16% and 33% by volume for the tested inhibition samples.
The testing found significant inhibition at both 16 and 33 percent concentrations. Moreover, the toxicity appeared linear in nature with a near doubling of inhibition with increased concentration. Given the test results, the new influent could cause significant upset to the biological treatment system.
Contact me if you would like more information on Tox-Bac™ testing and kit availability. Aster Bio will be making them available for sale in August 2016.
Erik Rumbaugh has been involved in biological waste treatment for over 20 years. He has worked with industrial and municipal wastewater facilities to ensure optimal performance of their treatment systems. He is a founder of Aster Bio (www.asterbio.com) specializing in biological waste treatment.
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