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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
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on study design:
INOCULUM/TEST ORGANISM
- Type of sludge: activated sludge
- Source: domestic waste water treatment plant
- Sampling site: sewage plant Groß-Zimmern, Germany
- Feeding: not applicable
- Method of cultivation: not applicable
- Preparation of inoculum: The activated sludge was washed by centrifugation and the supernatant liquid phase was decanted. The solid phase was resuspended in tap water and again centrifuged. This procedure was repeated twice
- Pretreatment: aeration with CO2-free air overnight
- Initial cell concentration: not measured
TEST SYSTEM
- Culturing apparatus: 5 l glas amber test flasks
- Number of culture flasks per concentration: 2
- Aeration device: CO2-free air production by leading air through 2 bottles, each containing about 500 ml NaOH (25% in water) to trap CO2. The CO2-free air was sparged through the scrubbing solutions at a rate corresponding to about 30-100 ml/min
- Measuring equipment: Absorption of the CO2 produced in the reactors in two bottles in series containing 200 ml 0.05 mol/l NaOH. CO2 determination by titration with 0.01M HCl using phenolphthalein as indicator
- Closed vessels used: not applicable
INITIAL TEST SUBSTANCE CONCENTRATION: 20.1 mg/l (14.5 and 14.4 mg DOC/l or TOC/l)
METHOD OF PREPARATION OF TEST SOLUTION: test substance was added directly into the test medium
DURATION OF THE TEST: 28 days
ANALYTICAL PARAMETER: mg of carbon dioxide trapped in sodium hydroxide solution
SAMPLING: on days 1, 4, 6, 8, 11, 14, 18, 21, 25, 28 and on day 29 after acidification
TEST CONDITIONS
- Composition of medium: according to OECD guideline 301
- Additional substrate: none
- Test temperature: 20 – 22 °C
- pH value: 7.6-8.0
- Aeration of dilution water: yes, aeration rate approx. 30-100 ml/minute
- Concentration of suspended solids: 30 mg/l dry solids
- Other relevant factors: none
INTERMEDIATES / DEGRADATION PRODUCTS: not measured
NITRATE/NITRITE MEASUREMENT: no
CONTROLS: blanks: two bottles with inoculum without test substance; toxicity control: one bottle with inoculum, reference substance and test item; procedure control: one bottle with reference substance and inoculum; abiotic control: one bottle with test substance in aqueous test medium
REFERENCE SUBSTANCE: aniline (25.1 mg/l; 19.4 mg/l TOC/l or DOC/L))
Key result
Parameter:
% degradation (CO2 evolution)
Value:
ca. 69
Sampling time:
28 d
Results with reference substance:
The reference item aniline degraded to 87% after 14 days , and to 99% after 28 days, thus confirming the suitability of the used activated sludge inoculum.
Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The percentage biodegradation exceeded 60% within the 10-day window. The test item can therefore be considered to be readily biodegradable.
Executive summary:

After 28 days the biodegradation of 2 -Butyl octanoic acid was 69 % in an OECD 301B-test. Also the percentage biodegradation exceeded 60% within the 10-day window. The test item can therefore be considered to be readily biodegradable.

Description of key information

After 28 days the biodegradation of the target substance 2 -Butyl octanoic acid was 69 % in an OECD 301B-test. Also the percentage biodegradation exceeded 60% within the 10-day window. The test item can therefore be considered to be readily biodegradable.This result is supported by a test of the source substance Reaction mass of n-undecanoic-acid and 2-methyl-decanoic-acid and 2-ethyl-nonanoic-acid and 2-propyl-octanoic-acid and 2-butyl-heptanoic-acid for which it was demonstrated to be readily biodegradable in an OECD 301B-test. 

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable
Type of water:
freshwater

Additional information

After 28 days the biodegradation of target substance 2 -Butyl octanoic acid was 69 % in an OECD 301B-test. Also the percentage biodegradation exceeded 60% within the 10-day window. The target substance can therefore be considered to be readily biodegradable.

Also the source substance Reaction mass of n-undecanoic-acid and 2-methyl-decanoic-acid and 2-ethyl-nonanoic-acid and 2-propyl-octanoic-acid and 2-butyl-heptanoic-acid was tested for ready biodegradation according to OECD 301B. The degradation of the source substance was 77.2 % within 28 days after acidification. The biodegradation of the read-across substance reached the criterion for ready biodegradation.