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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:
Feb. 27, 2013 - Jun. 17, 2013
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Version / remarks:
1992
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)
Version / remarks:
2008
Deviations:
no
Qualifier:
according to guideline
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, domestic (adaptation not specified)
Details on inoculum:
Activated sludge was obtained from a sewage plant treating predominantly domestic sewage (Nanjing Chengdong Sewage Treatment Plant) (Batch No.: AS20130227). On return to the laboratory the sludge was washed, centrifuged at 4°C, 10000 rpm for 10 min. The washing procedure was repeated 3 times. Thereafter, a small amount of the washed sludge was weighed and then dried at 100°C until the weight of the dried sludge did not
change significantly anymore. Then the dry weight percentage of suspended solids (p) of the activated sludge was calculated to be 10%. Finally 40g wet sludge centrifuged was mixed with 1 L the Based Salt Medium (BSM) to obtain an activated sludge with a mixed liquor suspended solids level of 4 g/L. (Batch No.: 120130308)
Duration of test (contact time):
28 d
Initial conc.:
40 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: 7.70 ~7.89

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
Key result
Parameter:
% degradation (O2 consumption)
Value:
< 1
Sampling time:
28 d
Results with reference substance:
76.0% in 14 days

Inoculum blank: O2 uptake 32 mg/L after 28 days (below 60 mg/L)

Reference Substance: 75.2 % after 28 days

Toxicity control: 29.4% after 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. Biodegradation of the reference substance and the results of the controls were within the validity criteria. Therefore, the test item has to be considered as not readily biodegradable under the conditions of this test.
Executive summary:

The test item was tested in a GLP-study according to OECD GL 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 32 mg O2/L at the end of the test, not exceeding 60 mg O2/L. Biodegradation of the reference substance sodium benzoate reached 75.2% 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 29.4% at 14 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 test item has to be considered as not readily biodegradable under the conditions of this test.

Key value for chemical safety assessment

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

Additional 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. Biodegradation of the reference substance and the results of the controls were within the validity criteria. Therefore, the test item has to be considered as not readily biodegradable under the conditions of this test.