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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:
July 16, 2013 - December 31, 2013
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Version / remarks:
1992
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)
Version / remarks:
2008
Deviations:
no
Qualifier:
according to
Guideline:
EPA OPPTS 835.3100 (Aerobic Aquatic Biodegradation)
Version / remarks:
1998
Deviations:
no
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: Nanjing Chengdong Sewage Treatment Plant, treating predominantly domestic sewage
- Preparation of inoculum for exposure: Sludge was washed and centrifuged at 4°C. Washing procedure repeated 3 times.
- Concentration of sludge: 4 g/L dw
- Initial cell/biomass concentration: 30 mg/L
Duration of test (contact time):
28 d
Initial conc.:
30 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: based salt medium
- Test temperature: 22 +- 1°C
- pH: 7.96 - 8.21

TEST SYSTEM
- Culturing apparatus: glass bottles 500 mL
- Number of culture flasks/concentration: 2

CONTROL AND BLANK SYSTEM
- Inoculum blank: 2 flasks
- Toxicity control: 1 flask
Reference substance:
benzoic acid, sodium salt
Test performance:
During the test, the temperature was kept at 22 ± 1 °C. The pH value of the content in the test container was maintained between 7.96 and 8.21. The total oxygen uptake in the inoculum blank was 19.9 mg O2/L at the end of the test, not exceeding 60 mg O2/L. Biodegradation of the reference substance, sodium benzoate, reached 76.0% in 14 days. The difference of replicate values for inoculum blank and test, during the test, was both less than 20%. Biodegradation of inhibition control was 37.3% at 14 days, indicating that there was no inhibition effect to inoculum. Thus, the test was considered to be valid.
Key result
Parameter:
% degradation (O2 consumption)
Value:
< 1
Sampling time:
28 d
Results with reference substance:
Biodegradation of the reference substance, sodium benzoate, reached 76.0% at 14 days.
Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
The ready biodegradability of the test item was determined in a study according to OECD 301F (Manometric Respirometry Test). The biodegradation was determined to be <1% after 28 d.
Executive summary:

The test item was tested in a GLP-study according to OECD 301F in a 28-day dissolved oxygen depletion test using secondary effluent from a domestic waste water treatment plant. During the test, the temperature was kept at 22 +/- 1°C. The total oxygen uptake in the inoculum blank was 19.9 mg O2/L at the end of the test, not exceeding 60 mg O2/L. Biodegradation of the reference substance sodium benzoate reached 76.0% at 14 days. The difference of replicate values for inoculum blank and test, during the test, was both less than 20%. Biodegradation of inhibition control was 37.3% at 28 days, indicating that there was no inhibition effect to inoculum. Thus, the test was considered valid. Under the valid conditions, biodegradation of the test item was < 1 %. The test item has to be considered as not readily biodegradable under the conditions of this test.

Description of key information

The ready biodegradability of the test item was determined in a study according to OECD 301F (Manometric Respirometry Test). The biodegradation was determined to be <1% after 28 d, no biodegradation was observed (reference 5.2.1 -1).

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed
Type of water:
freshwater

Additional information

The test item was tested in a GLP-study according to OECD 301F in a 28-day dissolved oxygen depletion test using secondary effluent from a domestic waste water treatment plant. During the test, the temperature was kept at 22 +/- 1°C. The total oxygen uptake in the inoculum blank was 19.9 mg O2/L at the end of the test, not exceeding 60 mg O2/L. Biodegradation of the reference substance sodium benzoate reached 76.0% at 14 days. The difference of replicate values for inoculum blank and test, during the test, was both less than 20%. Biodegradation of inhibition control was 37.3% at 28 days, indicating that there was no inhibition effect to inoculum. Thus, the test was considered valid. Under the valid conditions, biodegradation of the test item was < 1 %. The test item has to be considered as not readily biodegradable under the conditions of this test (reference 5.2.1 -1).