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Toxicity to microorganisms

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Description of key information

No significant inhibition of the respiratory rate of activated sludge by the addition of FAT 40481/A TE was observed at the nominal test concentration of 1000 mg/L. The EC15 obtained in the test was equal to or greater than 1000 mg/L.

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Additional information

The potential inhibition of the microbiological activity in activated sludge by the test substance FAT 40841/A TE was studied in an activated sludge respiration inhibition test in accordance with EU Method C.11. The test item, activated sludge inoculum and artificial wastewater were mixed in a glass beaker, incubated at 21 °C and continuously aerated for 3 hours. The nominal test concentration was 1000 mg/L. Aeration was stopped after 3 hours and the dissolved oxygen concentration in the test mixture was measured over a period of at least 10 minutes to deterine the inhibition of the respiration rate of the activated sludge. The test item had no significant inhibitory effect on the respiration rate at the test concentration of 1000 mg/L.

The oxygen consumption rates of the two controls (run at the start and end of the test) differed by 2%, which is less than the maximum allowable variation of 15%. The EC50 value for inhibition of the respiration test obtained in a parallel test with the reference substance 3,5 -dichlorophenol was 17 mg/L which is in the acceptable range of 5 to 30 mg/L. These results indicate that the test provided reliable results.