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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:
2008-12-09 to 2009-01-27
Reliability:
1 (reliable without restriction)
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
yes
Remarks:
A deviation to the study plan n°08/1124F was observed in this study: soda lime pellets were used instead of potassium hydroxyde pellets. There is no consequence on the results of this study
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, adapted
Details on inoculum:
Sample Site: Water treatment plant "Louis Fargue", Bordeaux (France)
Date of sampling : 200-12-09
Physico-chemical characteristic of inoculum:
Suspend solid: 2.4 g/L
pH: 7.1
Dissolved oxygen: 6.7mg/L
Activated sludge preparation:
- Filtration through a 5 mm sieve
- 3 successives decantations into mineral medium
- activated sludge aeration during 7 days

Duration of test (contact time):
ca. 28 d
Initial conc.:
100 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
Incolum control: Only inoculum
Reference item : Sodium benzoate 60.7 mg/L + inoculum
Toxicity control : test item 100mg/L + sodium benzoate 60.7 mg/L + inoculum
test item : 100 mg/L + inoculum

Study duration: 28 days
Light intensity: Darkness
Test temperature: 20°C +/- 1°C
Mineral medium composition (batch 7/15120801
Na2HPO4, 2H2o : 334 mg/L
K2HPO4 : 217.5 mg/L
NH4Cl : 5 mg/L
KH2PO4 : 85 mg/L
CaCl2, 2H2O : 36.4 mg/L
MgSO4, 7H2O : 22.5 mg/L
FeCL3, 6H2O : 0.25 mg/L
Reference substance:
benzoic acid, sodium salt
Test performance:
All validity criteria given by the OECD 301F guidelines were respected:
- Oxygen uptake of the inoculum control was not greater than 60 mg/L
- Variation between the two test item replicates was inferior to 20% at the end of the test.
- Reference item showed a biodegradability superior to 60% within 4 days
- Toxicity controls biodegradation was superior to 25% with 14 days
- pH values were comprised between 6 and 8.5.
Parameter:
% degradation (O2 consumption)
Value:
45.27
Sampling time:
10 d
Remarks on result:
other: without nitrification correction
Parameter:
% degradation (O2 consumption)
Value:
78.6
Sampling time:
28 d
Remarks on result:
other: without nitrification correction
Parameter:
% degradation (O2 consumption)
Value:
69.8
Sampling time:
28 d
Remarks on result:
other: With nitrification correction
Details on results:
No test item analysis in test item solutions has been made. However, nitrates and nitrites concentrations were determined at the start and the end of the study in the flask containing only test item.
Nitrate concentration (mg/L):
- T0: 1.15
- T28d: 17.6
Nitrate concentration (mg/L):
- T0 <0,01
- T28d: <0.01
Results with reference substance:
Reference Item showed a biodegradability superior to 60% within 4 days
Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable, but failing 10-day window
Conclusions:
Considering biodegradability with nitrification correction and the 60% pass level not reached in a 10 days window, the test item 1680JG canot be considered as a readily biodegradable substance.
Executive summary:

Ready biodegradability of the test item 1680JG was performed according to the OECD 301F guideline. The results obtained show that, without nitrification correction, the test item biodegradation reached 78.6% at the end of the study (i.e. 28days), the 60% pass level was almost reached in a 10 days window.

Howaver, as the test item contains N, a correction for oxygen uptake for interference by nitrification was needed. Considering biodegradability with nitrification correction and the 60% pass level not reached in a 10 days window, the test item 1680JG canot be considered as a readily biodegradable substance.

Description of key information

A ready biodegradability test of the substance was performed according to the OECD 301 F guidline.The results obtained show that, without nitrification corection, the test item biodegradation reached 78.6% at the end of the study(i.e.28 days), the 60% pass level was almost reached in a 10 days window.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable
Type of water:
freshwater

Additional information