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Environmental fate & pathways

Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2006
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Deviations:
no
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
sewage, predominantly domestic, adapted
Details on inoculum:
Activated sludge from the sewage plant at Hildesheim is well suited as it comprises mostly municipal sewage.
Municipal sewage treatment plant, 0-31137 Hildesheim
Colony forming units of the inoculum: 10(7) - 10(8) CFU/L

Pretreatment:
The activated sludge was washed twice with autoclaved tap water. After the second washing the settled sludge was filled up with mineral salts medium. For the 1st study the sludge was thereafter maintained in an aerobic condition by aeration with CO2 free air for 7 days. For the 2nd study the sludge was homogenized with a blender for 2 min after filling up with mineral salts medium. The supernatant was decanted and maintained in an aerobic
condition by aeration with CO2 free air for 2 days. In both stud ies 10mL/L were used to initiate inoculation.
Duration of test (contact time):
28 d
Initial conc.:
15 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
CO2 evolution
Reference substance:
benzoic acid, sodium salt
Parameter:
% degradation (CO2 evolution)
Value:
18.8
Sampling time:
28 d
Remarks on result:
other: study 1 replicate 1
Parameter:
% degradation (CO2 evolution)
Value:
81
Sampling time:
28 d
Remarks on result:
other: study 1 replicate 2
Parameter:
% degradation (CO2 evolution)
Value:
94
Sampling time:
28 d
Remarks on result:
other: study 2 replicate 1
Parameter:
% degradation (CO2 evolution)
Value:
21.6
Sampling time:
28 d
Remarks on result:
other: study 2 replicate 2
Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The test item must be regarded as readily biodegradable in the 10-d-window and after 28 days. The test item complies with the biodegradability criteria as laid down in Annex III of Regulation (EC) No 648/2004 on detergents.
Executive summary:

The biodegradability was determined with a non adapted activated sludge for the test item over a test period of 28 days in the Modified Sturm Test. Two independent studies were conducted according to OECD 301B/CO2 evolution test.

The test item was tested with a concentration of 15 mg/L in duplicates. The biodegradation of the test item was followed by titrimetric analyses of the quantity of CO2 produced by the respiration of bacteria.

The degradation was finished on day 28 by acidification, the last titration was made on day 29, after the soluble CO2 was turned out over a period of 24 h. The percentage CO2 production was calculated in relation to the theoretical CO2 (ThCO2 ) of the test item. The biodegradation was calculated for each titration time.

Two studies were performed because the difference in the results of the replicates was > 20%.

In the 1st study the 2nd test item replicate reached the 10 % level (beginning of biodegradation) after 8 days and the pass level of 60 % after 18 days. The biodegradation came to a maximum of 81 % after 28 days. The 2nd test item replicate reached the 10 % level after 21 days. The pass level of 60 % was not reached until day 28. The biodegradation came to a maximum of 17 % after 28 days.

In the 2nd study the 1st test item replicate reached the 10 % level (beginning of biodegradation) after 9 days and the pass level of 60 % after 14 days. The biodegradation came to a maximum of 96 % after 28 days. The 2nd test item replicate reached the 10 % level after 11 days. The pass level of 60 % was not reached until day 28. The biodegradation came to a maximum of 19 % after 28 days. It is assumed that the difference of both replicates in each study is due to the low solubility of the test item.

Description of key information

The test item must be regarded as readily biodegradable in the 10-d-window and after 28 days. The test item complies with the biodegradability criteria as laid down in Annex III of Regulation (EC) No 648/2004 on detergents.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information