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Toxicity to microorganisms

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Description of key information

Depending on local conditions and existing concentrations, disturbances in the biodegradation process of activated sludge are possible. The nitrification performance of activated sludge during the elimination via sewage treatment plants may be interfered.

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Additional information

In a GLP short-term respiration test according to OECD 209 conducted with 1,4-Dimethyl-1H-pyrazole (CAS 1072-68-0) an EC10 (180 min) of 1.1 mg/L (3h EC50 = 10 mg/L) was obtained for nitrification inhibition (3h values of 1.9 mg/L (EC10) and 110 mg/L (EC50) were determined for total oxygen uptake). The test was performed using domestic activated sludge.

The 3h EC10 value for nitrification inhibition (1.1 mg/L) was used for the derivation of the PNEC-STP.