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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:
21/07/2011 to 04/10/2011
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Version / remarks:
1992
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)
Version / remarks:
2008
Deviations:
no
GLP compliance:
yes (incl. certificate)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: Bois-de-Bay, Satigny, Switzerland
- Storage conditions: aerobic
- Storage length: sludge collected in the morning and used same day
- Preparation of inoculum for exposure: washed 3 times by centrifugation
- Dry weight suspended solids: diluted to 1.53 g/L
Duration of test (contact time):
28 d
Initial conc.:
30 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Remarks:
measuring pressure drop
Details on study design:
TEST CONDITIONS
- Composition of medium: according to OECD 301 guideline
- Test temperature: 22.3 - 22.9 °C
- pH: 7.6 at start of experiment
- pH adjusted: no
- Suspended solids concentration: 1.53 g/L (activated sludge)

TEST SYSTEM
- Culturing apparatus: Oxitop Control System by Wissenschaftlich-Technische Werkstätten (WTW), Weilheim, Germany
- Number of culture flasks/concentration: 6 flasks
* 2 flasks: inoculum + test substance 30 mg/L
* 2 flasks: inoculum
* 2 flasks: inoculum + reference substance 100 mg/L
- Measuring equipment:
- Test performed in closed vessels: yes
- Details of trap for CO2 and volatile organics if used: 2 sodium hydroxide pellets

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Abiotic sterile control: no
- Toxicity control: no

STATISTICAL METHODS: not specified
Reference substance:
benzoic acid, sodium salt
Key result
Parameter:
% degradation (O2 consumption)
Value:
64
St. dev.:
1
Sampling time:
12 d
Parameter:
% degradation (O2 consumption)
Value:
74
St. dev.:
1.5
Sampling time:
28 d
Details on results:
The 10-day window criterion is fulfilled: more than 60 % is degraded within the 10-day window.
The test substance did not inhibit the intrinsic respiration of the inoculum.


Parameter:
ThOD
Value:
2.2 mg O2/g test mat.

Biodegradation over time:

day % biodegradation
1 1
2 15
7 53
12 64
14 65
21 72
28 74

Erroneously high oxygen consumption was observed for one of the flasks with reference substance. The results of this flask were not considered. Still this is not considered as guideline deviation as a single procedure control is sufficient according to OECD 301F.

Validity criteria:

Difference between replicate values < 20 % (i.e. maximally 4%) + Oxygen uptake in 28 days < 60 mg/L (i.e. maximally 38 %) + Degradation of reference substance exceeded 40 % after 7 days and 65 % after 14 days, activity of inoculum was thus verified.

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The test substance degrades more than 60 % within the 10-d window and should thus be regarded as readily biodegradable.
Executive summary:

In this study, the ready biodegradability of the test substance was assessed according to OECD 301F guideline, manometric respirometry. In this study the activity of the inoculum was verified and confirmed using sodium benzoate as reference substance. The validity criteria were all met. The study concludes that the 10 -d window criterion is fulfilled for the test substance since 15 % biodegraded on day 2 and 64 % on day 12. After 28 days incubation, the test substance underwent 74 % biodegradation. Thus, the test substance should be regarded as readily biodegradable.

Description of key information

The test substance should be regarded readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

For this endpoint, one study is available (Kreutzer, 2011) in which the readily biodegradability of the test substance is assessed according to OECD 301F. The study results show that 67 % of the test substance is biodegraded after 28 days and that the 10-d window criterion is fulfilled.