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Environmental fate & pathways

Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
EU Method C.5 (Degradation: Biochemical Oxygen Demand)
Qualifier:
according to guideline
Guideline:
EU Method C.6 (Degradation: Chemical Oxygen Demand)
GLP compliance:
yes (incl. QA statement)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge (adaptation not specified)
Duration of test (contact time):
>= 28 d
Initial conc.:
>= 0.99
Initial conc.:
>= 1.98
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
Test substance was added on a filter to the stoppered test bottles which were then filled with the natural seawater medium. Concurrent controls were also established. The oxygen concentration was measured using an oxygen electrode after 5, 20 and 28 days. Temperature, pH was also recorded.
Reference substance:
other: ethanol
Test performance:
The mean maximum biochemical oxygen demand of 0.12 mg O2/mg was reached after 20 days.
Remarks on result:
other: see BOD5 results below
Parameter:
BOD5
Value:
0.07 mg O2/g test mat.
Remarks on result:
other: test conc. 1.98 mg/l
Parameter:
COD
Value:
3 other: %
Remarks on result:
other: test conc. 1.98 mg/L
Parameter:
BOD5
Value:
0.11 mg O2/g test mat.
Remarks on result:
other: test conc. 0.99 mg/L
Parameter:
COD
Value:
4
Remarks on result:
other: test conc. 0.99 mg/L
Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
The degradation of Donor C20 appeared to be low, being <= 5% based on it's COD or ThOD value. Donor C20 is considered to not be biodegradable in this test.
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Qualifier:
according to guideline
Guideline:
other: GB/T 21831-2008: Chemicals-Ready Biodegradability Closed Bottle Test
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Shanghai Longhua Sewage Plant
- Preparation of inoculum for exposure: Aeration of the secrdary effluent for 7 days at the test temperature of 20 +/- 1C
- Concentration of sludge: 1.4 x 105 orgs/L
Duration of test (contact time):
28 d
Initial conc.:
4 mg/L
Based on:
ThOD
Details on study design:
TEST CONDITIONS
- Composition of medium: Mineral Medium,
a) KH2PO4 8.50g; K2HPO4 21.75g; NaHPO4-2H2O 334g; NH4Cl 0.5g. Dissolved in water and make up to 1 litre, pH 7.4
b) CaCl2 27.50g. Dissolved and make up to 1 litre
c) MgSO4.7H2O 22.50g. Dissolved and make up to 1 litre
d) FeCl.6H20 0.25. Dissolved and make up to 1 litre
1 mL of of solutions a), b), c) and d) with 800 ML and then make up to 1 litre
- Test temperature: 20C +/- 1C
- Aeration of dilution water: No

TEST SYSTEM
- Number of culture flasks/concentration: 2
- Measuring equipment: DIssoved oxygen meter (Model YSI-58)
- Test performed in closed vessels due to significant volatility of test substance: Yes
- Test performed in open system: No

SAMPLING
- Sampling frequency: 1d, 4d, 7d, 14d, 18d, 21d, 24d, 28d
- Sterility check if applicable: No

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Toxicity control: yes

STATISTICAL METHODS:
Not applicable
Reference substance:
benzoic acid, sodium salt
Parameter:
% degradation (O2 consumption)
Value:
2.9
Sampling time:
28 d
Remarks on result:
other: mean of replicates (duplicates)
Details on results:
The validity criteria of the test was met:
Blank control: O2 consumption was 0.8 mg/ DO/l (did not exceed 1.5 mg DO/l after 28 days)
Reference substance: Degradation >60% after 14 days
Toxicity control: O2 consumption of the toxicity contro after 14 days was 3.5 mg/L (greater than reference group 3.4 mg/L
Residual O2 concentration : did not fall below 0.5 mg/l throughout the test
Replicates: Difference was less than 20%

No inhibition observed in the toxicity control
Results with reference substance:
See table below

% Degradation results 

         Test substance   Reference substance
 1d  Replicates  0.7 0.4   -  -
 1d  Average 0.5     -    
 4d   Replicates  1.6 1.3   -
 4d   Average     1.4     -
 7d   Replicates  2.0 1.8   80.8 80.5 
 7d   Average 1.9     80.7    
 11d   Replicates  2.1 2.0   -
 11d   Average 2.1         -
 14d   Replicates  2.6 2.3   87.1 86.8 
14d    Average 2.5         87.0
 18d   Replicates  2.8 2.7   -
 18d   Average     2.7  -   
 21d   Replicates  3.1 2.4   88.8 88.2 
 21d   Average     2.8     88.5
 24d   Replicates  3.2 2.5   -
 24d   Average     2.9 -    
 28d   Replicates  3.0 2.7   88.9 89.5 
 28d   Average     2.9     89.2
Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
The test substance was not ready biodegradable in this test.

Description of key information

Two reliable studies were available to determine biodegradability of the substance. Using different guideline methods, the results indicate that the substance is not biodegradable with <5% biodegradation seen at the end of the test within each study.

Key value for chemical safety assessment

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

Additional information