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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

The effect of the test material on the respiration of activated sewage sludge micro-organisms prepared by direct dispersion in water gave a 3-Hour EC50 of greater than 1000 mg/l. Correspondingly the No Observed Effect Concentration (NOEC) was 1000 mg/l.

Key value for chemical safety assessment

EC50 for microorganisms:
1 000 mg/L
EC10 or NOEC for microorganisms:
1 000 mg/L

Additional information

Methods:

A study was performed to assess the effect of the test material on the respiration of activated sewage sludge. The method followed that described in the OECD guidelines for testing of Chemicals (1984) No 209, EEC Commission Directive 87/302/EEC and US EPA Ecological Effects Test Guidelines OPPTS 850.6800.

Procedure:

Following preliminary range-finding studies activated sewage sludge was exposed to an aqueous dispersion of the test material at concentrations of 1000 mg/l (three replicate flasks) and 0.80 mg/ (single flask) for a period of 3 hours at 21 deg C with the addition of a synthetic sewage as a respiratory substrate.

The rate of respiration was determined after 30 minutes and 3 hours contact time and compared to data for the control and a reference material, 3,5 -dichlorophenol.

In order to satisfy the requirements of all Competent Authorities worldwide, the definitive study was conducted using two methods of dispersing the test material in the test system; one using a single test concentration of 0.80 mg/l prepared using a preliminary solution in auxiliary solvent, the other two using a test concentration of 1000 mg/l prepared by direct dispersion in water with the aid of ultrasonication.

Results:

In the single test vessel prepared using a preliminary solution in auxiliary solvent to give a test concentration of 0.80 mg/l (the limit of visual solubility) no significant inhibition of the respiration rate of activated sewage was observed and hence the 3 hour EC50 value was determined to be greater than 0.80 mg/l. These results show that at the limit of visual solubility of the test material, the test material has no effect on the respiration rate of activated sewage sludge.

The effect of the test material on the respiration rate of activated sewage sludge at concentrations in excess of the visual solubility level of the test material was also assessed using a single test concentration of 1000 mg/l prepared by direct dispersion of the test material in water with the aid of ultrasonication. At a test concentration in excess of the visual solubility level of the test material in water with the aid of ultrasonication. At a test concentration in excess of the visual solubility level of the test material inhibition of respiration of the activated sewage sludge did not occur and the 3-hour EC 50 value was determined to be greater than 1000mg/l. Correspondingly the NOEC was determined to be 1000mg/l. These results show that at a concentration in excess of the visual solubility level of the test material, the test material does not have an effect on the respiration rate of activated sewage sludge.