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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:
11/02/97 - 13/3/97
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Deviations:
yes
Remarks:
See principles of method
Principles of method if other than guideline:
According to the OECD method 301B, CO2 should be removed from the test flask after the addition of the inoculum but before the addition of the test substance. As the test substance is only sparingly soluble, it was added directly to the test flasks and dispersed into emulsion, with CO2 removed before the addition of the inoculum.
GLP compliance:
yes
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
No data reported
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
Inoculum was taken from a urban biological water treatment plant in Versailles. The inoculum was retrieved 2 days prior to test initation and aerated then centrifuged at 20°C for 20 minutes at 4000g.The final inoculated medium was diluted to a concentration of 1.5 E5 bacteria/ml.
Duration of test (contact time):
28 d
Initial conc.:
15 mg/L
Based on:
other: TOC
Initial conc.:
45.1 mg/L
Based on:
test mat.
Initial conc.:
82.6 mg/L
Based on:
other: CO2 Th
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
Inocluated mineral medium containing set concentrations of test substance was kept in the dark and aerated by passing CO2 through it. The test substance (at concentrations of between 10 and 20 mg/l of COD or TOC) was degraded by micro-organisms, as their sole carbon and energy source, through organotrophic chemotherapy. The degradation was recorded by analysing the CO2 produced over the 28 days of the test. Measurements were made on days 0, 1, 4, 6, 8, 11, 14, 22, 27 and 28. The inhibitory effects of the substance were determined by measuring degradation, through CO2 release, in a flask with reference substance, test substance and inoculum. After the CO2 traps were renewed on the last day of testing, the test flasks were acidified with 1ml of concentrated hydrochloric acid in order to release the CO2, and after 24 hours, the barium hydroxide was titrated.
Reference substance:
other: The reference substance, sodium benzoate (57.7% C), was 3.9 mg/ml was diluted in the test medium, giving 39mgCOD or a mass of 82.5 theoretic CO2 mgCO2Th. In the inhibition control, equilavents quantities of test substance and reference were introduced, gi
Preliminary study:
No data reported
Test performance:
DEGRADATION: 13% after 28 days.
Parameter:
% degradation (CO2 evolution)
Value:
13
Sampling time:
28 d
Parameter:
% degradation (CO2 evolution)
Value:
45
Sampling time:
14 d
Remarks on result:
other: Reference substance in inhibition control
Parameter:
% degradation (CO2 evolution)
Value:
47
Sampling time:
28 d
Remarks on result:
other: Reference substance in inhibition control
Details on results:
According to the OECD guideline 301, the test substance cannot be considered as readily biodegradable.
Results with reference substance:
No inhibition of inoculum observed.
Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
Biodegradation was 13% after 28 days, therefore polysulfides, di-tert-butyl, is not considered readily biodegradable.
Executive summary:

Thiebaud (1997) is a 28 day, aerobic, GLP-compliant, ready biodegradability carbon dioxide evolution test with aerobic domestic activated sludge and control groups, following OECD guideline 301B. The study is considered reliable and suitable for use as a key study for this endpoint.

Description of key information

Biodegradation was 13% after 28 days, therefore polysulfides, di-tert-bu, is not considered readily biodegradable.

Key value for chemical safety assessment

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

Additional information

Thiebaud (1997) is a 28 day, aerobic, GLP-compliant, ready biodegradability carbon dioxide evolution test with aerobic domestic activated sludge and control groups, following OECD guideline 301B. The study is considered reliable and suitable for use as a key study for this endpoint.