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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

The inhibition of the degradation activity of activated sludge is not anticipated when introduced to biological treatment plants in appropriate low concentrations. 

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Additional information

To assess the inhibitory concentration of the test substance in aerobic bacteria, an activated sludge respiratory inhibition test was conducted. Therefore, activated sludge from a domestic sewage treatment plant was used. The sludge was separated from the aqueous layer by settling instead of centrifugation. Further preparation was carried out as described in guideline EEC L 133, p.118-122 (1988) except for the following deviation: Due to the poor solubility of the test substance at test concentrations, no stock solution was prepared and the test substance was given directly into the medium. The test concentrations were 104.5, 32, 16, 3.3 and 1.1 mg/L (nominal). 3,5-Dichlorophenole was used as reference substance and tested in the concentrations 32, 10 and 3.2 mg/L. As a result, the EC50 value as well as the EC80, EC20 and NOEC values were >100 mg/L.