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Toxicity to microorganisms

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Description of key information

Activated sludge respiration test as WAFs loading: EL10 39.52 mg/l (OECD 209, GLP).

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
39.52 mg/L

Additional information

The aim of the study was to determine the effect of the test substance to microorganisms by measuring the respiration rate under defined conditions and in the presence of different WAF loadings of the test substance. This key study is classified as reliable and the test fulfils all validity criteria mentioned in OECD 209 guidelines and it was conducted in compliance with GLP.

Preliminary test was conducted with WAF-loading rates 10 mg/L, 100 mg/L, 1000 mg/L and as a limit test WAF loading rate 2000 mg/L. As a result EL10 for total inhibition was determined as 39.52 mg/L and EL10 for heterotrophic nitrification was determined as 28.64 mg/L. Based on the results of both tests it can be concluded that the activated sludge was slightly inhibited by the test substance. Because the highest total inhibition was only 13.75 % (WAF loading 2000 mg/L), the EL50 was estimated to be >2000 mg/L.