Registration Dossier

Environmental fate & pathways

Biodegradation in water: screening tests

Administrative data

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

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2011
Report Date:
2011

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
no
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid: particulate/powder

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Totnes sewage treatment works, Totnes, Devon, UK.
- Storage conditions: Aerated at room temperature
- Storage length: Not specified.
- Preparation of inoculum for exposure: Seven days prior to the exposure start the activated sludge was centrifuged, washed and resuspended in the test medium and the solids concentration determined. This sludge was then diluted in medium, added to test bottles and stirred until required for use.
- Concentration of sludge: 30 mg/L (27 mg/L in toxicity controls)

Duration of test (contact time):
28 d
Initial test substance concentration
Initial conc.:
100 mg/L
Based on:
COD
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: Standard mineral medium as per the relevant OECD guideline
- Additional substrate: None
- Solubilising agent (type and concentration if used): None
- Test temperature: 22 +/- 2°C
- pH: 7.4 to 7.5 in the test substance bottles
- pH adjusted: No
- Aeration of dilution water: Yes (continuous stirring)
- Suspended solids concentration: 30 mg/L
- Continuous darkness: yes (amber glass used)

TEST SYSTEM
- Culturing apparatus: Glass BOD bottles
- Number of culture flasks/concentration: triplicate
- Method used to create aerobic conditions: Continuous stirring
- Measuring equipment: Oxitop respirometers
- Test performed in closed vessels due to significant volatility of test substance: Test is conducted closed as standard
- Test performed in open system: No
- Details of trap for CO2 and volatile organics if used: Absorped by potassium hydroxide solution in the neck of the flasks.

SAMPLING
- Sampling frequency: Automatically sampled every 112 minutes.
- Sampling method: Oxitop bottles contain pressure sensors automaticaaly detect O2 consumption by a reduction in pressure.
- Sterility check if applicable: Not applicable
- Sample storage before analysis: Not applicable

Reference substance
Reference substance:
benzoic acid, sodium salt

Results and discussion

Preliminary study:
Not applicable
Test performance:
The results of the reference substance showed that 77% biodegradation was observed after 28 days which confirmed the suitability of the assay. The toxicity control also showed that the test substance did not inhibit biodegradation and the oxygen uptake of controls was below the prescribed level as per the OECD guidelines.
% Degradation
Parameter:
% degradation (O2 consumption)
Value:
< 5
Sampling time:
28 d
Details on results:
The results showed the biodegradation of the test substance was minimal (< 5%)

BOD5 / COD results

Results with reference substance:
77% biodegradation of sodium benzoate was observed at 28 days.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
As less than 5% biodegradation was observed after 28 days of contact time, the substance is considered not to be readily biodegradable under the conditions employed in the test.