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Diss Factsheets

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
Study period:
1 (reliable without restriction)

Data source

Reference Type:
study report

Materials and methods

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

Test material


Study design

Oxygen conditions:
Inoculum or test system:
other: inoculum based on aerated sludge
Details on inoculum:
inoculum collected from a water treatment plant, containing effluent from predominantly domestic origin and then aerated for 6 days. Inoculum concentration : 12.0 mg/L (dry weight) in all test vessels.
Duration of test (contact time):
28 d
Details on study design:
The test item was dissolved in reconstituted water (OECD mineral medium) prepared from deionised water with a conductivity < 10 microS/cm.
Five flasks were used to determine the quantity of carbon dioxide evolved by the degradation of the test item:
- two flasks containing the inoculum (inoculum blanks),
- two flasks containing the test item (at 10.0 mg/L of total organic carbon (TOC) and inoculum (test solutions)
- one flask containing the reference item (sodium acetate at 10.0 mg/L of TOC) and inoculum (procedure control)
Measurements of CO2: days 1, 4, 6, 8, 11, 14, 19, 22, 25 and 29.

The inoculum consisted of sewage sludge sampled from the aeration tank of a sewage treatment plant and then aeratedfor days. Inoculum concentration was 12.0 mg/L (dry weight) in all test vessels.
CO2 scrubbed air was bubbled through the flasks over the test period.
Environmental parameters were recorded as:
pH: 7.54 to 7.93,
temperature: 20 to 24 C.
Reference substance
Reference substance:
acetic acid, sodium salt

Results and discussion

% Degradation
Sampling time:
28 d
Remarks on result:
other: over the whole test period
Details on results:
Cumulative percentage of biodegradation: See table in Overall remarks and attachements window.

Applicant's summary and conclusion

Validity criteria fulfilled:
At the end of the test, the biodegradation of Thiofestermet reached 12%. Thiofestermet is therefore not readily biodegradable in the 28-day modified Sturm test.