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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:
02/04/2012-11/07/2012
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reason / purpose:
reference to same study
Reference:
Composition 0
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)
Principles of method if other than guideline:
/
GLP compliance:
yes
Test material information:
Composition 1
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure):collected from the Cambridge Wastewater Treatment Facility, Cambridge, Maryland, 19/04/2012
- Storage conditions:at 20°C for
- Storage length:48h
- Preparation of inoculum for exposure: A total suspended solids measurement and standard plate count were performed on the inoculum on the day of use in the test.
- Pretreatment: sludge was sieved using a 2-mm screen, adjusted to approximately 1,000mg total suspended solids/L with mineral media and then aerated at test temperature until use.
- Concentration of sludge: 1000mg/L suspended solids/L mineral media
- Water filtered: yes
- Type and size of filter used, if any:2-mm screen
Duration of test (contact time):
28 d
Initial conc.:
10 mg/L
Based on:
IC (inorganic carbon)
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Composition of medium:
a modified biochemical oxygen demand (BOD) test dilution water
- Test temperature:20°C
- Suspended solids concentration: <=30mg/l

TEST SYSTEM
- Culturing apparatus:amber 4-liter bottles
- Number of culture flasks/concentration: 3
- Method used to create aerobic conditions:All chambers were aerated with CO2-free air for approximately 24 hours at a rate of 50 to 100 mL per minute to purge the systems of CO2.
- Measuring equipment:Shimadzu Model TOC-Vcsh carbon analyzer to measure CO2 trapped as K2CO3 in the KOH solution
- Details of trap for CO2 and volatile organics if used: CO2 trap, contains approximately 100 mL of 0.5 M KOH, connected to the exit air lines of each chamber.


SAMPLING
- Sampling frequency:3, 6, 9, 13, 17, 20, 23 and 27 days
- Sampling method: removing the Co2 trap nearest the test chamber


CONTROL AND BLANK SYSTEM
- Inoculum blank: not dosed with a carbon source
- Other:Reference group: a reference substance sodium benzoate, a substance known to be biodegradable, was used to check the viability of the inoculum

Test performance:
The control chambers evolved an average of 65.0 mg CO2 over the test period. This value has been corrected for the amount of CO2 in the trapping solution since potassium hydroxide solution, even when freshly prepared, contains carbonates. The amount of CO2 evolved by the blank control chambers did not exceed the 40 mg/L (120 mg total) value considered the acceptable limit for CO2 evolution tests.
Key result
Parameter:
% degradation (CO2 evolution)
Value:
-2.4
Sampling time:
28 d
Results with reference substance:
The viability of the inoculum and validity of the test were supported by the results of the reference substance, sodium benzoate, from which an average of 101.8% of theoretical CO2 was evolved. An average percent biodegradation of greater than 60% was achieved by Day 6, thereby fulfilling the criteria for a valid test by reaching the pass level by Day 14. The final mean percent biodegradation for Brominated Epoxy was -2.4%. Brominated Epoxy may not be considered readily biodegradable, since the pass level of 60% ThCO2 was not achieved.

The temperature range recorded during the test was 19.3-20.8°C and was within the protocol specified range throughout the test. The average TSS of the activated sludge on the day of collection was 12,687 mg/L. The results of the standard plate count and TSS measurement performed on the inoculum were 1.1 x 106 CFU/mL and 900 mg/L, respectively.

Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
Evidence of ready biodegradability in a Carbon Dioxide Evolution Test is 60% ThCO2 within the 28-day test period. In addition, the pass level must be reached within 10 days of achieving 10% ThCO2. The final mean percent biodegradation for Brominated Epoxy was –2.4%. Brominated Epoxy may not be considered readily biodegradable since the pass level of 60% ThCO2 was not achieved. Thus, F-2200 which is the main component in Brominated Epoxy mixture (~70%) is also may not be considered readily biodegradable as well.
Executive summary:

The ready biodegradability of Brominated Epoxy was determined by the Carbon Dioxide Evolution Test Method (OECD Guideline 301B). Tests of ready biodegradability are stringent tests that provide limited opportunity for acclimation and biodegradation to occur. In the CO2 test, inoculated mineral medium was dosed with a known amount of test substance as the nominal sole source of organic carbon and aerated with CO2-free air. The CO2 produced from the mineralization of organic carbon within the test chambers was displaced by the flow of CO2-free air and trapped as K2CO3 in KOH trapping solution. The amount of CO2 produced by the test substance (corrected for that evolved by the blank inoculum) is expressed as a percentage of the theoretical amount of CO2 (ThCO2) that could have been produced if complete biodegradation of the test substance occurred. The test contained a blank control group, a reference group and a treatment group. Each group contained three replicate test chambers. The blank control was used to measure the background CO2 production of the inoculum and was not dosed with a carbon source. The reference chambers were dosed with sodium benzoate, a substance known to be biodegradable, at a nominal concentration of 10 mg C/L. The treatment group test chambers were used to evaluate Brominated Epoxy at a nominal concentration of 10 mg C/L. The results indicated that the activated sludge inoculum was active, degrading the reference substance an average of 101.8%. The average cumulative percent biodegradation for Brominated Epoxy was –2.4%. Thus, F-2200 which is the main component in Brominated Epoxy mixture (~70%) is also  may not be considered readily biodegradable as well.

Description of key information

Evidence of ready biodegradability in a Carbon Dioxide Evolution Test is 60% ThCO2

within the 28-day test period. In addition, the pass level must be reached within 10 days of achieving 10% ThCO2. The final mean percent biodegradation for Brominated Epoxy was –2.4%. Brominated Epoxy may not be considered readily biodegradable since the pass level of 60% ThCO2 was not achieved. Thus, F-2200 which is the main component in Brominated Epoxy mixture (~70%) is also  may not be considered readily biodegradable as well.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information