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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:
02 Sep - 10 Oct 2005
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
EU Method C.4-E (Determination of the "Ready" Biodegradability - Closed Bottle Test)
Version / remarks:
92/69
Deviations:
no
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/sludge: secondary effluent of a domestic sewage treatment plant (Wupper area water authority, STP Odenthal)
- Preparation of inoculum for exposure: effluent concentration in reaction mixture was 5 mL/L
- Pretreatment: separation of coarse particles by filtration, aeration of mineral medium plus inoculum (filtrate) for 5 days
Duration of test (contact time):
28 d
Initial conc.:
2.6 mg/L
Based on:
ThOD
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: mineral medium
- Test temperature: 22 °C +/- 2 °C
- Aeration of dilution water: Aeriation for 5 days

TEST SYSTEM
- Culturing apparatus: closed bottles
- Number of culture flasks/concentration: 10
- Method used to create aerobic conditions: aeriation of the solution

SAMPLING
- Sampling frequency: 7, 14, 21, 28 days

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes, 10 replicates
- Toxicity control: yes, 10 replicates (containing test item, reference substance and inoculum)
- Procedure control: yes, 10 replicates (sodium benzoate)
Reference substance:
benzoic acid, sodium salt
Key result
Parameter:
% degradation (O2 consumption)
Value:
7
Sampling time:
28 d
Parameter:
% degradation (O2 consumption)
Value:
4
Sampling time:
21 d
Parameter:
% degradation (O2 consumption)
Value:
7
Sampling time:
14 d
Parameter:
% degradation (O2 consumption)
Value:
1
Sampling time:
7 d
Details on results:
The toxicity control showed 31% and 33% degradation after 14 days and 28 days, respectively. The used concentration of the test substance did not show toxic effects to bacteria.
Results with reference substance:
The reference substance (sodium benzoate) showed 74 % and 77 % degradation after 14 days and 28 days, respectively.

Validity criteria for the measurement of the biodegradation:

























Target condition according to guideline:Actual condition according to the study:Validity criteria met:
In order to check the procedure, reference compounds which meet the criteria for ready biodegradability are tested by setting up an appropriate vessel in parallel as part of normal test runs. Suitable compounds are aniline (freshly distilled), sodium acetate and sodium benzoate.Benzoic acid, sodium salt was used as a reference compound.Yes
A test is considered valid if the difference of extremes of replicate values of the removal of the test chemical at the plateau, at the end of the test or at the end of the 10-d window, as appropriate, is less than 20 % and if the percentage degradation of the reference compound has reached the pass
levels by day 14.

The % degradation of the two measured values of the test substance at the end of the test (28 d) range between 1 - 7 %


There was 74 % degradation of the reference substance after 14 d - the pass level (60 % for ThOD) was reached.


Yes
If in a toxicity test, containing both the test substance and a reference compound, less than 35 % degradation (based on total DOC) or less than 25 % (based on total ThOD or ThCO2) occurred within 14 days, the test substance can be assumed to be inhibitory. The test series should be repeated, using a lower concentration of test substance (if this can be done without seriously impairing the accuracy of the DOC determination) and/or a higher concentration of inoculum, but not greater than 30 mg solids/L.The used concentrations of the test substance did not show toxic effects to bacteria (after 7, 14, 21 and 28 d, 29 %, 31 %, 32 %, and 33 % degradation were measured based on ThOD).Yes

 

Validity criteria fulfilled:
yes
Remarks:
See 'Any other information on results incl. tables'.
Interpretation of results:
not readily biodegradable
Conclusions:
The test substance showed 7 % degradation after 28 days. Therefore, the test substance is considered to be ''Not Readily Biodegradable'.
Executive summary:

The study was performed to asses the ready biodegradability of the test substance. The study was conducted in accordance with 92/69/EEC Method C.4-E: Closed Bottle Test. This test method is in all essential parts identical with OECD Guideline 301 D. The test substance (2.6 mg/L nominal concentration) in a mineral medium was inoculated with secondary effluent and incubated for 28 days under aerobic conditions in completely full, closed bottles. During this period the biodegradation is followed by analysis of dissolved oxygen. The amount of oxygen taken up by the test chemical, corrected for uptake by the blank inoculum run in parallel, is expressed as a percentage of theoretical oxygen demand (ThOD). The test substance showed 1 %, 7 %, 4 %, and 7 % degradation after 7, 14, 21, and 28 days respectively. Therefore, the test substance is considered to be 'Not Readily Biodegradable'. The used concentration of the test substance did not show toxic effects to bacteria.

Description of key information

A study was performed to asses the ready biodegradability of the test substance. The study was conducted in accordance with 92/69/EEC Method C.4-E: Closed Bottle Test. This test method is in all essential parts identical with OECD Guideline 301 D. The test substance (2.6 mg/L nominal concentration) in a mineral medium was inoculated with secondary effluent and incubated for 28 days under aerobic conditions in completely full, closed bottles. During this period the biodegradation is followed by analysis of dissolved oxygen. The amount of oxygen taken up by the test chemical, corrected for uptake by the blank inoculum run in parallel, is expressed as a percentage of theoretical oxygen demand (ThOD). The test substance showed 1%, 7%, 4%, and 7% degradation after 7, 14, 21, and 28 days respectively. Therefore, the test substance is considered to be 'Not Readily Biodegradable'. The used concentration of the test substance did not show toxic effects to bacteria.

Key value for chemical safety assessment

Biodegradation in water:
not biodegradable
Type of water:
freshwater

Additional information