Sofia University: Assessment of impaired biological activity during the landfill leachate treatment and toxicity reduction by plasma treatment

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Determination of metabolic activity of test bacteria by fluorescence intensity. @UNISOFIA

Sofia University created and repeatedly applied a test to evaluate the toxicity of the complex pollutant PFAS, of leachate and of leachate with the addition of PFOA. The test is based on an assessment of the reduced biological activity of a standardized 18-hour test bacterial culture of Escherichia coli due to the impact of the different toxic pollutants tested: Leachate with complex PFAS, leachate from a Sofia solid waste treatment plant and leachate enriched with various concentrations of PFOA.

The biological activity (respectively the toxicity) is evaluated by fluorescence techniques after staining with CTC and DAPI dyes. The intensity of fluorescence corresponding to the metabolic activity of the test culture, the shape of the bacterial cells, as well as the percentage of remaining metabolically active cells after the toxic effect are simultaneously monitored.

The results show that the leachate, the model liquid with high concentration of PFOA and the leachate with PFOA have significant toxicity, proportional to the concentration of the tested toxicants. The results are confirmed for the three parameters of the intoxication process - metabolic activity, cell size, percentage of metabolically active cells.

Treatment of the investigated toxic agents with plasma produced by different electrical discharges reduces both individual and complex toxicity and improves the biological characteristics of the tested bacterial culture.

The plasma technology is a promising tool for toxicity reduction of complex pollutant including PFAS in landfill leachate which is one of the goals of the PROMISCES project.


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Detection of morphological changes by calculation of the mean perimeter of the test bacteria. @UNISOFIA

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Investigation of the fluorescence characteristics of the bacterial suspension affected and not affected by PFAS and plasma treatment. @Simon Varsano


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Cultivation and standardization of microbial suspension from Escherichia coli. @Simon Varsano