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:
other: GLP guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1998
Report Date:
1999

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
- Source of inoculum/activated sludge: secondary effluent from municipal treatment plant handling domestic sewage
- Preparation of inoculum for exposure: inoculum was aerated by means of a magnetic stirrer
- Concentration of sludge: 5 mL inoculum per 1 L test solution
- Water filtered: yes
- Type and size of filter used, if any: coarse paper filter (folded filter)
Duration of test (contact time):
28 d
Initial test substance concentration
Initial conc.:
2.05 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: mineral medium according to OECD 301
- Test temperature: 22 +/- 2°C
- pH: 7.4 +/- 0.2
- pH adjusted: yes
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: temperature controlled incubator
- Number of culture flasks/concentration: 3
- Method used to create aerobic conditions: pre-aeration of mineral nutrient solution
- Measuring equipment: Oximeter with oximatic electrode

SAMPLING
- Sampling frequency: days 0, 7, 14, 21, 28
- Sampling method: each sample was discarded following sampling

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Toxicity control: yes, 50% test substance, 50% reference substance
Reference substance
Reference substance:
benzoic acid, sodium salt

Results and discussion

Test performance:
The maximum oxygen depletion within the inoculum blank was 0.54 mg/L and after 28 days the residual concentration of oxygen in all bottles was > 0.5 mg/L.
The toxicity control showed a degradation rate of 40% indicating no cytotoxicity from the test substance to the inoculum used. Thus, the valididy criteria given in the OECD test guideline are met and the study is considered valid.
% Degradation
Parameter:
% degradation (O2 consumption)
Value:
< 10
Sampling time:
28 d
Details on results:
The toxicity control showed a degradation rate of 40% indicating no toxicity of the test substance to the inocculum.

Kinetic of test substance (in %):
0 after 7 day(s)
0 after 14 day(s)
2 after 21 day(s)
1 after 28 day(s)

BOD5 / COD results

Results with reference substance:
The reference substance sodium benzoate was degraded by 87% within 28 days; the criteria for "ready degradability" of equal or more than 60% was met within 7 days.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Remarks:
according to OECD 301 D
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
Under the conditions of this study on ready biodegradability the test substance was not biodegradable. The study is considered valid.