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Biodegradation in water: screening tests

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biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP guideline study
according to guideline
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
GLP compliance:
yes (incl. QA statement)
Oxygen conditions:
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: Municipal activated sludge from a wastewater treatment plant.
- Preparation of inoculum for exposure: a aliquot of activated sludge suspension was sieved (mesh size = 1mm). After settling the supernatant was discarded and sludge was filled up with water.
- Concentration of sludge: 6 g/L
Duration of test (contact time):
28 d
Initial conc.:
20 mg/L
Based on:
other: TOC
Initial conc.:
30 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
- Composition of medium: 1500 ml test solution contained ca. 30 mg/L test substance (44.8 mg/vessel, 20 mg/L TOC), 19.5 ml mineral medium, 7.5 ml inoculum
- Test temperature: 22 ± 2 °C
- pH:
- study initation: 7.4
- study end: 7.2 - 7.3

- Culturing apparatus: 2 L incubation bottles, filled up to a volume of 1.5 L
- Number of culture flasks/concentration: 3
- Method used to create aerobic conditions: aeration performed with CO2 free air at a flow of approx. 800 ml per hour
- Details of trap for CO2 and volatile organics if used: Bottles were connected to two serial scrubbing bottles (total volume 250 ml) filled with 100 ml 0.05 sodium hydroxide solution.

- Sampling frequency: twice a week

- Inoculum blank: 2
- Inhibition control: 1
- Reference substance: 1

Reference substance:
Key result
% degradation (CO2 evolution)
60 - 70
Sampling time:
28 d
Details on results:
- 10-day window was failed

- Duration of the adaption phase: 2 d
- Degradation degree of the inhibition control after 14 days: 67%
Results with reference substance:
- Degradation degree of the reference substance after 14 days: 71%

Since Kerocom FM 38 is a mixture, the application of the 10-day window criterion is not scientifically justified.

Validity criteria fulfilled:
Interpretation of results:
readily biodegradable

Description of key information

Readily biodegradable: >60% CO2 evolution in 28 days (OECD 301B)

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

In a CO2 evolution test according to OECD guideline 301 B the biodegradation of the test substance was investigated (BASF SE, 2009). After 28 days > 60 % degradation was determined. The degradation degree was not reached within the 10 - day window; however, the application of the 10-day window criterion is not scientifically justified for UVCB substances since sequential degradation can be assumed. Exceeding the pass level (60 % Degradation based on CO2 evolution) within the standard test duration of 28 days is considered to be sufficient to evaluate the described UVCB substance as readily biodegradable.