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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
Study period:
JUL - NOV 2008
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Qualifier:
according to
Guideline:
EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)
GLP compliance:
yes
Specific details on test material used for the study:
white powder with a purity of 99.82%
Oxygen conditions:
aerobic
Inoculum or test system:
sewage, predominantly domestic, non-adapted
Details on inoculum:
The freshly obtained sludge was kept under continuous aeration until further treatment. The concentration of suspended solids was 4.3 g/1 in the concentrated sludge (information obtained from the municipal sewage treatment plant). Before use, the sludge was allowed to settle (35 minutes) and the liquid was decanted for use as inoculum at the amount of 10 ml/I of mineral medium.
Duration of test (contact time):
> 0 - <= 28 d
Initial conc.:
36.3 mg/L
Based on:
TOC
Initial conc.:
36 mg/L
Based on:
TOC
Details on study design:
Since AHU377 C9 was not sufficiently soluble to allow preparation of an aqueous solution at a concentration of 1 g/1, weighed amounts of AHU377 C9 were added to the test bottles (2 litres) containing medium with microbial organisms and mineral components (test substance bottle A:
36.3 mg; test substance bottle B: 36.0 mg and toxicity control bottle: 35.8 mg). To this end, 10 ml of Milli-RO water was added to each weighing bottle containing the test substance. After vigorous shaking the resulting suspension was added quantitatively to the test medium. This treatment was repeated 3 times. The test solutions were continuously stirred during the test, to ensure optimal contact between the test substance and the test organisms.

Titrations were made every second or third day during the first 10 days, and thereafter at least every fifth day until the 28th day, for the inoculum blank and test
suspension. Titrations for the positive and toxicity control were made at least 14 days.
Each time the CO,-absorber nearest to the test bottle was removed for titration; each of the remaining two absorbers was moved one position in the direction of
the test bottle. A new CO,-absorber was placed at the far end of the series. Phenolphthalein (1 % solution in ethanol, Merck, Darmstadt, Germany) was used as
pH-indicator.
On the 28th day, the pH of all test suspensions was measured and 1 ml of concentrated HCI (37%, Merck, Darmstadt, Germany) was added to the bottles of the
inoculum blank and test suspension. The bottles were aerated overnight to drive off CO2 present in the test suspension. The final titration was made on day 29.
Key result
Parameter:
% degradation (CO2 evolution)
Value:
>= 7 - <= 8
Sampling time:
29 d
Details on results:
Theoretical CO2 production
The ThC02 of AHU377 C9 was calculated to be 2.45 mg CO2/mg.
The ThC02 of Sodium Acetate was calculated to be 1.07 mg CO2/mg.

The temperature recorded in a vessel with water in the same room varied between 20.8 and 22.5'C.
Results with reference substance:
In the toxicity control more than 25% biodegradation occurred within 14 days (34%, based on
ThC02). Therefore, the test substance was assumed not to inhibit microbial activity.
Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
AHU377 C9 was not readily biodegradable under the conditions of the modified Sturm test presently performed.

Description of key information

AHU377 C9 was not readily biodegradable under the conditions of the modified Sturm test presently performed.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed
Type of water:
freshwater

Additional information