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Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
2005-10-19 to 2006-01-17
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
The purity of the test substance is not indicated.
Qualifier:
according to
Guideline:
OECD Guideline 306 (Biodegradability in Seawater)
Version / remarks:
1992
Deviations:
no
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
natural water: marine
Details on inoculum:
- Source of inoculum/activated sludge: Populations of bacteria which occur naturally in seawater. The raw seawater used for this study was supplied by a submersible pump situated on Sutherland's pier on the west side of Flotta in Scapa Flow. It is pumped continuously from a depth of two metres below low water spring tide level, before passing up 1.8 kilometres of plastic pipe to a 20,000 litre storage tank.
Duration of test (contact time):
28 d
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: According to guideline
- Test temperature: 20 +/- 1 °C, seawater temperature: 6-14 °C in the summer
- Salinity: 34 and 37 %.

TEST SYSTEM
- Culturing apparatus: 272 mL glass BOD bottles
- Number of culture flasks/concentration: 3, minimum of 2 per timepoint for data processing

CONTROL AND BLANK SYSTEM
- Toxicity control: yes, to enable an assessment of potential inhibitory effects of the test material (or its primary degradation products), an inhibition control is used, in which a mixture of the soluble reference compound and the test material is tested.

STATISTICAL METHODS: The overall assessment of biodegradability is based upon a comparison between experimentally determined oxygen consumption (BOD measurements) and the oxygen consumption predicted if all carbon present in the test material were completely oxidised (theoretical oxygen demand, ThOD).
Reference substance:
benzoic acid, sodium salt
Preliminary study:
Not performed
Key result
Parameter:
% degradation (O2 consumption)
Value:
88
Sampling time:
28 d
Details on results:
The test was conducted in accordance with the study plan and met all relevant validity criteria. There were no interferences in this test. The test substance biodegraded by 88% over 28 days and showed an inhibition of 15% to seawater bacteria. The oxygen blank was within formal limits of acceptability.
Results with reference substance:
The soluble reference material, sodium benzoate, degraded by more than 60% in the first ten days, indicating that the seawater used in the test contained a satisfactory population of viable bacteria.
Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 A (Ready Biodegradability: DOC Die Away Test)
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Duration of test (contact time):
8 d
Initial conc.:
50.7 mg/L
Based on:
test mat.
Initial conc.:
20 mg/L
Based on:
DOC
Parameter followed for biodegradation estimation:
DOC removal
Reference substance:
aniline
Key result
Parameter:
% degradation (DOC removal)
Value:
>= 90 - <= 100
Sampling time:
8 d
Details on results:
lag phase: 1 day
start of plateau phase: day 3

Elimination by adsorption: less than 10% after 1 day.

Abiotic elimination: less than 10% after 8 days.

The reference substance (aniline) was functional.
Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable

Description of key information

Four readily biodegradable studies according to OECD criteria are available. Three studies were tested with freshwater one was tested with salt water. As a result the test substance is classified as readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Four studies performed with freshwater according to OECD guideline 301 and OECD guideline 310 are available. One further study performed with salt water according to OECD guideline 306 was performed. 

 

Freshwater

Key

The readily biodegradability of the test substance was determined in a study according to OECD guideline 301 A. As inoculum activated sludge, domestic, non-adapted was used. The initial concentration was 50.7 mg/L test material and 20.0 mg/L DOC. Aniline was used as reference substance. A degradation of 90 – 100 % was determined after 8 days. The substance is ready biodegradable.

Supporting

The ready biodegradability of the test substance was determined in a study according to OECD guideline 301 C. Activated sludge was used as inoculum. An initial concentration of 100 mg/L was used. The test showed a degradation of 89.0 – 95.0 % after 10 days. A further supporting study according to OECD guideline 310 is available. The test showed a degradation of 84 % at the end of the test.

Saltwater

Supporting

The ready biodegradability of the test substance was tested in an OECD guideline study. This method employs no separate bacterial innoculum, and relies upon populations of bacteria which occur naturally in seawater. The overall assessment of biodegradability is based upon a comparison between experimentally determined oxygen consumption (BOD measurements) and the oxygen consumption predicted if all carbon present in the test material were completely oxidised (theoretical oxygen demand, ThOD). To enable an assessment of potential inhibitory effects of the test material (or its primary degradation products), an inhibition control is used, in which a mixture of the soluble reference compound and the test material is tested. The test substance biodegraded by 88% over 28 days and showed an inhibition of 15% to seawater bacteria. The oxygen blank was within formal limits of acceptability. The soluble reference material, sodium benzoate, degraded by more than 60% in the first ten days, indicating that the seawater used in the test contained a satisfactory population of viable bacteria.The test substance is ready biodegradable.

 

Conclusion: Four OECD guideline studies showed biodegradation rates of 84 % - 100 %. The substance is classified as readily biodegradable.