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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:
Dec. 2010 - Feb. 2011
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
Qualifier:
according to
Guideline:
EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)
Version / remarks:
2008
GLP compliance:
yes (incl. certificate)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of activated sludge: from a wastewater treatment plant (ARA Ergolz II, Füllinsdorf, Switzerland) treating predominantly domestic wastewater
- Pretreatment: washed twice with tap water by centrifugation and the supernatant liquid phase was decanted. A homogenized aliquot of the final sludge suspension was weighed, thereafter dried and the ratio of wet to dry weight was calculated.
- Concentration of sludge: 4 g (±10%) dry material per liter
Duration of test (contact time):
28 d
Initial conc.:
100 mg/L
Based on:
test mat.
Initial conc.:
> 220 - < 222 other: mg O2/L
Based on:
ThOD
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Composition of medium: test water (according to guidelines)
- Solubilising agent: no
- Test temperature: 22 °C
- pH: 7.4 - 7.7
- pH adjusted: yes, for test water (7.8 to 7.4)
- Suspended solids concentration: final concentration of 30 mg dry material per liter
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 500 mL reaction vessels
- Number of culture flasks/concentration: 2
- Measuring equipment: The CO2 is adsorbed by soda lime, which results in a decrease of the total pressure in the airtight test flasks. The pressure drop is detected and converted into an electrical signal by means of an electrode type manometer.

SAMPLING
- Sampling frequency: at least on each working day

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Procedure control: sodium benzoate
- Toxicity control: sodium benzoate and test item
Reference substance:
benzoic acid, sodium salt
Key result
Parameter:
% degradation (CO2 evolution)
Value:
86
Sampling time:
28 d
Details on results:
After 7 days a degradation of 56 % was determined, after 14 days a degradation of 77 %, after 21 days a degradation of 84 % and after 28 days a degradation of 86 %. The 10 day window was passed. The degradation of the toxicity control was 78 % after 28 days. No toxicity of the test substance was observed in the toxicity control.
Results with reference substance:
In parallel preparations with the reference substance, sodium benzoate showed a degradation of 65 % was achieved within 14 days.
Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
Within the test period of 28 days, a degradation of 86 % was determined for the test item.
Executive summary:

The biodegradation of the test item was determined in a manometric respirometry test according to EU method C.4 D and OECD 301 F. The test substance is suspended in test medium, inoculated with activated sludge of a domestic WWTP and incubated for 28 days under aerobic conditions in the dark at 22 °C. During this period, the biodegradation of the test substance is determined on the basis of the generation of CO2. Within the test period of 28 days, a degradation of 86 % was determined. The degradation of the toxicity control was 78 % after 28 days. No toxicity of the test substance was observed in the toxicity control.

Description of key information

In a manometric respirometry test the biodegradation of the test item was determined to be 86 % after 28 days, therefore it was considered to be readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

The biodegradation of the test item was determined in a manometric respirometry test according to EU method C.4 D and OECD 301 F. The test substance is suspended in test medium, inoculated with activated sludge of a domestic WWTP and incubated for 28 days under aerobic conditions in the dark at 22 °C. During this period, the biodegradation of the test substance is determined on the basis of the generation of CO2. Within the test period of 28 days, a degradation of 86 % was determined. The degradation of the toxicity control was 78 % after 28 days. No toxicity of the test substance was observed in the toxicity control.