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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:
2012.08.16 - 2012.09.13
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
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
sewage, domestic (adaptation not specified)
Details on inoculum:
secondary effluent from a municipal wastewater treatment plant in Usserød, Denmark, wihich predominantly receives domestic sewage
Duration of test (contact time):
28 d
Initial conc.:
2.2 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
The study was performed with aerobic activated sludge from a wastewater treatment plant (Usserød, Denmark). The necessary volume of the test medium with minerals was prepared. The medium was aerated to an initial cincentration of approx. 9 mg O²/l and inoculated with 0.5 ml secondary effluent/l
Reference substance:
benzoic acid, sodium salt
Key result
Parameter:
% degradation (O2 consumption)
Value:
3.3
Sampling time:
7 d
Key result
Parameter:
% degradation (O2 consumption)
Value:
2.4
Sampling time:
14 d
Key result
Parameter:
% degradation (O2 consumption)
Value:
6.7
St. dev.:
2.1
Sampling time:
21 d
Key result
Parameter:
% degradation (O2 consumption)
Value:
2.1
St. dev.:
1
Sampling time:
28 d
Key result
Parameter:
COD
Value:
200 other: mg/l

Biodegradation of test substance and reference substance tested seperately and in combination.

 TimeDays  Test product "Danafloat TM 262 (IPETC)" % of ThOD Activity controlsodium benzoate  % of ThOD Toxicity control "Danaflost TM 262 (IPETC)+ sodium benzoate% of ThOD 
 7 3.3  65.2  31.0 
 14 2.4  72.6  35.4 
 21 6.7  76.9  36.5 
 28 2.1  71.2  35.1 
Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
The substance was found to be not biodegradable under the test conditions within the 28-day exposure period.
Executive summary:

Test substance was tested in a concentration of 2.2 mg/l and reference substance in a concentration of 2.0 mg/l.

The substance was found to be not biodegradable under the test conditions within the 28-day exposure period.

The oxygen consumption in the activity control showed that the activity of the inoculum was satisfactory.

In the toxicity control containing both the test substance and the reference item sodium benzoate no inhibitory effect on microorganisms in inoculum was observed.

In the procedure controls the reference item sodium benzoate was readily biodegraded by an average of 72.6 % within 14 days of exposure; thus confirming suitability of the activated sludge

Description of key information

The test item can not be considered readily biodegradable.
The pass level for ready biodegradability, 60% of ThOD, was not accomplished during 28 days.
After 21 days ThOd corresponded to 6.7 ±2.1 % . After 28 days the value was 2.1±1%.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information