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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:
from 2000-06-27 to 2000-07-25
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method C.4-E (Determination of the "Ready" Biodegradability - Closed Bottle Test)
Deviations:
no
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: Mixed population of aquatic microorganisms of the secondary effluent of a domestic sewage treatment plant (Odenthal, Germany)
- Preparation of inoculum for exposure: The coarse particles were separated by filtration the mineral medium plus inoculum (filtrate) were aerated for 4 days.
- Concentration of sludge: 5 mL/L
- Water filtered: yes
Duration of test (contact time):
28 d
Initial conc.:
2.4 mg/L
Based on:
test mat.
Initial conc.:
2 947 other: mgO2/g (ThOD)
Based on:
ThOD
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: Secondary effluent of a domestic sewage treatment plant (Odenthal, Germany) plus mineral medium.
- Type of the test vessels: closed
- Test temperature: 20 +/- 1 °C
- Aeration of dilution water: yes

TEST SYSTEM
- Culturing apparatus: Waterbathes, incubators
- Number of test suspension: 10 bottles.
- Number of procedure control flasks: 10 bottles. In order to check the procedure, the reference chemical sodium benzoate was tested by setting up 2 flasks in parallel to the normal tests runs.
- Number of inoculum blank flasks (measured volume of mineral medium containing only inoculum): 10 bottles
- Number of toxicity control flasks: 10 bottles. The toxic effects of the test substance are determined in a toxicity control flask (containing test substance, reference substance and inoculum).
- Measuring equipment:
Oxygen measuring instrument
Balances
pH measuring instrument
Waterbathes, incubators
Cooling system
Direct weighing
Oxygen measurement
pH measurement
Closed Bottle Test

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes. Mineral medium containing only inoculum
- Abiotic sterile control: No
- Toxicity control: yes. The toxicity control contained the test substance, reference substance and inoculum.

Reference substance:
benzoic acid, sodium salt
Preliminary study:
Not performed
Test performance:
No unusual observations during the study.
Key result
Parameter:
% degradation (O2 consumption)
Value:
16
Sampling time:
28 d
Details on results:
The test substance showed 16 % degradation after 28 days, therefore the test substance is considered not ready biodegradable.
Results with reference substance:
The reference compound showed 78 % degradation after 14 days. The validity criteria was fulfilled.
Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
At the end of the test, after 28 days the test substance was biodegraded by 16 %, therefore the test substance is classified as not readily biodegradable.
Executive summary:

The ready biodegradability of the test substance was investigated according to the OECD guideline 301D: Closed bottle test (1992). At the end of the test, after 28 days the test substance was biodegraded by 16 %, therefore the test substance is classified as not readily biodegradable. No inhibitory effect on the microorganisms was observed at a concentration of 2.4 mg/L. The validity criteria were met.

Description of key information

The test substance was biodegraded by 16 % over 28 days. The test substance is classified as not readily biodegradable according to the OECD criteria.

 

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

The ready biodegradability of the test substance was investigated according to the OECD guideline 301D: Closed bottle test (1992). The biodegradation of the test substance was followed by exposing it in a mineral medium and incubated for 28 days under aerobic conditions. At the end of the test, after 28 days the test substance was biodegraded by 16 %, therefore the test substance is classified as not readily biodegradable. No inhibitory effect on the microorganisms was observed at a concentration of 2.4 mg/L. The validity criteria were met.