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Environmental fate & pathways

Biodegradation in water: screening tests

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biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1991-06-04 to 1991-08-01
1 (reliable without restriction)
equivalent or similar to guideline
EU Method C.5 (Degradation: Biochemical Oxygen Demand)
not applicable
Principles of method if other than guideline:
adaptation of the method C5 ( 1994): modified sturm test
GLP compliance:
yes (incl. QA statement)
Oxygen conditions:
Inoculum or test system:
activated sludge (adaptation not specified)
Details on inoculum:
- organisms, strains: a mixture of different strains of microorganisms found in activated sludge from a municipal sewage treatment plant receiving little or no industrial effluent (form Pierre Bénite - 69310 Lyon - France)
On arrival at the laboratory, the activated sludge was aerated for 4 hours: 500 ml of the mixture were sampled and homogenised for approximately 2 minutes with magnetic stirring. It was then allowed to settle for 2 periods of 30 minutes approximately ; 1% inoculation of each test flask with the supernatant was then made the same day.
Duration of test (contact time):
ca. 28 d
Initial conc.:
ca. 20 mg/L
Based on:
other: ThCO2
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
- temperature of the test room : from 22.5°C to 23.5°C
- test volume : 3L which was aerated at the rate of 1 to 2 bubbles per second
- containers : 5 litre carboys (clear glass). Containers were covered with a dark material
- the study was conducted in darkness
- 3 assays were involved: 1 assay with the test substance at 20 mg/L
1 assay with reference substance at the concentration of 20 mg/L
1 control assay without any test substance
- determination of CO2 production for each assay every 2 days for the first 10 days, then every 3 or 5 days until the 28th day.

Test performance:

total production of C02 in control study: 29.26 mg of C02

pH measurement:
- Control: D0=8.73 and D28=7.7
-Test substance: D0=7.99 and D28=5.71
- Reference substance: D0=8.52 and D28=7.93
% degradation (CO2 evolution)
ca. 39.16
Sampling time:
4 d
% degradation (CO2 evolution)
ca. 97.38
Sampling time:
28 d
Details on results:
% ThCO2 (biodegradation) of the test product at 20 mg/L:
D2 = 4.95
D4 = 30.96
D6 = 55.94
D8 = 67.53
D10 = 77.77
D15 = 97.38
D20 = 97.72
D25 = 97.72
D28 = 97.72
Results with reference substance:
% biodegradation of the reference substance (sodium acetate 290 mg/L): 84.4% in 28 days
Validity criteria fulfilled:
Interpretation of results:
readily biodegradable
A biodegradability of the test substance (20 mg/L) of 97.38% in 28 days was obtained under the experimental conditions.
Executive summary:

A modified Sturm test protocol was performed to evaluation the readily biodegradability of the test substance.

The test substance was tested at 20 mg/L. Sodium acetate at 20 mg/L was used as reference product. A control assay, without test substance, was performed in the same conditions.

The degradation of the test substance was evaluated by comparing the quantity of CO2 generated in the test medium with that in the control assay in relation to the total CO2 that the substance could have theoretically produced (based on the content of the test substance).

The quality criteria for the study, notified in the E.E.C protocol and relative to the biodegradation of these test substance and to the total production of CO2 in the control assay, were respected.

Taking into account the results obtained under the experimental conditions employed the evaluation of the biotic degradation of the test substance using the Modified Sturm test showed:

a biodegradability of the test substance of 97.38% in 28 days at 20 mg/l with respect of the 10 day window.

The CO2 released and incorporated as BaCO3 was measured every 2 days over a 10 day period and then every 2 days over a 10 day period and then 3, 5 days until the 28th day.

Description of key information

A biodegradability of the test substance (20 mg/L) of 97.38% in 28 days was obtained according to Modified Sturm Test (E.E.C: 84/449 - Annex V Method C5 (1984)).

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable
Type of water:

Additional information