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Description of key information

DOWFAX 8390-D surfactant inhibition to activated sludge respiration EC50 was > 284 mg/l.

Key value for chemical safety assessment

EC50 for microorganisms:
284 mg/L

Additional information

Dry form of DOWFAX 8390 -D surfactant was studied for possible bactericidal effects with the activated sludge inhibition assay according to the OECD Guidelines No. 209 and to Directive 67/548/EEC, ammended Nov. 18, 1987 (87/302), Part C. The effect of the test material on the respiration rate of activated sludge from a municipal waste water treatment plant was determined by comparing the oxygen consumption of samples treated with 5 different concentrations of the test material (25, 50, 100, 200 and 284 mg/l). The test substance showed a slight inhibitory effect on aerobic waste water bacteria, the inhibition ranging from 11 to 25 % at 25 and 200 mg/l, respectively. Since the slowly increasing inhibitory effect seemed to level-off at the highest concentration tested (only 26 % inhibition at 284 mg/l) the EC50 value for DOWFAX 8390 -D surfactant could not be determined (i.e., EC50 > 284 mg/l). The control with 3,5 -dinitrophenol showed an EC50 value of 6 mg/l indicating suitability of the used test conditions.

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