The discharge of industrial effluents into urban collection systems and subsequent treatment at wastewater treatment plants (WWTPs) is common practice. An ongoing challenge is to evaluate the toxicity of incoming mixtures of industrial and municipal streams to WWTPs in order to identify and prevent potential process upsets. For example, the microorganisms involved in nitrification – the biologically mediated process responsible for the conversion of ammonia to nitrate – are highly susceptible to the presence of biocides that are commonly added to industrial process waters to inhibit microbial growth. Currently, available toxicity detection techniques either take too long (e.g. 48-96 hours for LC50, 4-6 hours for specific nitrification rate (SNR) tests), require sophisticated and expensive equipment (e.g. liquid chromatography, flow cytometry), or are unable to detect small variations between process waters (e.g. Microtox, LUMIStox).  To address these shortcomings, we have developed a simple biosensor (&lt;10 minutes) using the following: three to seven pure strains of microorganisms found in WWTPs, off-the-shelf nucleic acid stains which probe for the metabolism and membrane integrity of the strains, a portable hand-held fluorometer to cater to point-of-use testing. Recently developed preservation techniques using water-soluble sugars (e.g. pullulan) have also allowed us to preserve this biosensor at room or refrigerated temperatures for at least 2 months with no significant change in cell survival. In this study, we report results from two phases of testing using this technology. One phase consisted of testing surrogate WWs containing commercially-available biocides (e.g., Grotan® BK) and other known nitrification inhibitors (e.g., phenol). In the other phase, real industrial WWs were tested to allow for the use partial least squares, due to the complex nature of the WW, to predict toxicity based on the SNR test. Overall, the outcomes are substantial, as the technology allows for a cost-effective determination of the toxicity of biocide-containing WWs.

Rapid and simple assay to detect the presence of biocides that inhibit nitrification

2019 Fall National Meeting

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