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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

The ready biodegradability of the test item was determined with a non-adapted activated sludge over a test period of 28 days in the Modified Sturm Test according to OECD 301 B.The test item was tested at a concentration of21 mg/L with 2 replicates corresponding to a carbon content (TOC) of10.1 mg C/L in the test vessels.The test vessels were incubated at low light conditions and at a temperature of 20 – 24 °C.

The biodegradation of the test item was followed by titrimetric analysis of the quantity of CO2produced by the respiration of bacteria. The degradation was stopped on day 28 by acidification of the test solutions. The last titration was made on day 29 after residual CO2had been purged from the test solutions over a period of 24 hours. The percentage CO2production was calculated in relation to the theoretical CO2production (ThCO2) of the test item. The biodegradation was calculated for each titration time.

 

To check the activity of the test system sodium benzoate was used asfunctional control. The percentage degradation of the functional control reached the pass level of 60 % within 8 days and a biodegradation of 86 % after 28 days.

In thetoxicity controlcontaining both test and reference item a biodegradation of 28 % was determined within 13 days and it came to 44 % after 28 days. The biodegradation of the reference item was not inhibited by the test item in thetoxicity control.

The biodegradation of thetest itemwas evaluated in copmarison to the readily degradable functional control and the toxicity control. The mean 10 % level (beginning of biodegradation) was reached on day 28. The 60 % pass level was not reached by both test item replicates until test end. The mean biodegradation on day 28 was 12 %.

 

 

The test item is classified asnot readily biodegradablewithin the 28 day period of the study.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed
Type of water:
freshwater

Additional information