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Environmental fate & pathways

Biodegradation in water: screening tests

Administrative data

biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference Type:
study report
Report Date:

Materials and methods

Test guideline
according to
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
GLP compliance:
yes (incl. certificate)

Test material

Details on test material:
- Name of test material (as cited in study report): pyranyl acetate pure
- Physical state: Liquid/ colorless to yellowish; clear
- Analytical purity: 99.0 corr. area-%
- Lot/batch No.: ZH 146
- Expiration date of the lot/batch: Dec 2015
- Water solubility: 814 mg/L at 20 °C
- Stability under test conditions: stable
- Storage condition of test material: Storage at room temperature

Study design

Oxygen conditions:
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure):
Municipal activated sludge from the wastewater treatment plant of Mannheim, Germany.
The inoculum was collected on 07 August 2015 from the aeration tank of the plant. A suitable aliquot of the activated sludge suspension was sieved by a finely woven mesh with a mesh size about 1 mm. To reduce the content of inorganic carbon in the blank
controls the activated sludge was aerated with carbon dioxide free air for about 72 hours at 22 ± 2° C.

- Preparation of inoculum for exposure: At the day of exposure the suspension was washed one time with drinking water.
Therefore the aeration was stopped and the sludge was allowed to settle. After settling the supernatant was discarded and the remaining sludge suspension was filled up with drinking water and the concentration oft the sludge was adjusted to 6.0 g/L dry weight. Aliquots of 7.5 mL were added to the test vessels to obtain an activated sludge concentration of 30 mg/L dry weight.

Duration of test (contact time):
28 d
Initial test substance concentrationopen allclose all
Initial conc.:
20 mg/L
Based on:
other: TOC
Initial conc.:
30 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
- Composition of medium: complies with the test guideline OECD 301B
- Test temperature: 22 ± 2° C
- pH: 7.1-7.4

- Culturing apparatus: 2 L incubation bottles filled up to a volume of 1.5 L.
- Number of culture flasks/concentration: 2
- Details of trap for CO2 and volatile organics if used: The Carbon Dioxide Evolution Test was performed in 2 L incubation bottles filled up to a volume of 1.5 L. The bottles were connected to two serial scrubbing bottles (total volume 250 mL) filled with 100 mL 0.05 mol sodium hydroxide solution for the adsorption of carbon dioxide from biodegradation processes. Usually twice a week the Total Inorganic Carbon (TIC) values of the adsorption solutions of the first trap were determined and used for the calculation of the produced carbon dioxide. After each sampling the second trap was moved forward and the new trap with fresh sodium hydroxide solution was placed into the second position. Each trap was analyzed separately

- Sampling frequency: Usually twice a week

- Inoculum blank: 2
- inhibition control test assay: 1 (IH)

Reference substance
Reference substance:

Results and discussion

% Degradation
other: CO2/ThCO2
80 - 90
Sampling time:
28 d

BOD5 / COD results

Results with reference substance:
Degree of biodegradation of the reference substance after 14 days: 75 % CO2/ThCO2

Applicant's summary and conclusion

Validity criteria fulfilled:
Interpretation of results:
readily biodegradable, but failing 10-day window
The conclusion that pyranyl acetate pure was not readily biodegradable in this carbon dioxide evolution test based on the quantitative determination of the formed arbon dioxide in the test substance assays by comparison with the calculated maximal theoretical carbon dioxide production.