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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
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: GLP study according to protocol. The CoA included in the report did not contain enough detail on composition; a statement of the composition is attached to the robust summary.
Qualifier:
according to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Deviations:
yes
Remarks:
prolonged measurements
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
Secondary activated sludge was obtained from the WWTP Nieuwgraaf in Duiven, The Netherlands (30-03-2001). The WWTP Nieuwgraaf is an activated sludge plant treating predominantly domestic waste water. A minor deviation of the test procedures described in the guidelines was introduced: instead of an effluent/extract/mixture, activated sludge was used as an inoculum. The activated sludge was preconditioned to reduce the endogenous respiration rates. To this end, 200 mg Dry Weight (DW)/L of activated sludge was aerated for one week. The sludge was diluted to a concentration of 2 mg DW/L in the BOD bottles.
Duration of test (contact time):
42 d
Initial conc.:
4 mg/L
Based on:
test mat.
Initial conc.:
2.2 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: The nutrient medium of the Closed Bottle test contained per liter of deionized water: 8.5 mg KH2PO4, 21.75 mg K2HPO4, 33.4 mg Na2HPO4•2H2O, 22.5 mg MgSO4•7H2O, 27.5 mg CaCl2, 0.25 mg FeCl3•6H2O. Ammonium chloride was omitted from the medium to prevent nitrification. Due to this omission the pH of the medium decreased slightly. The decrease of the pH does not effect the biodegradation in the Closed Bottle test.
- Test temperature: Temperatures ranged from 19.0 to 21.2°C.
- pH: The pH of the media ranged from 6.9 to 7.0 at the start of the test. The pH of the medium at day 28 varied from 6.6 to 6.9.
- pH adjusted: no
- Aeration of dilution water: no data
- Continuous darkness: yes
- Other: The test substance and sodium acetate were added to the bottles using stock solutions of 1.05 and 1.0 g/L, respectively. Solvent was added to the bottles using a stock solution of 0.54 g/L.

TEST SYSTEM
- Culturing apparatus: The test was performed in 250 to 300 ml BOD (biological oxygen demand) bottles with glass stoppers.
- Number of culture flasks/concentration: 10
- Method used to create aerobic conditions: no data
- Measuring equipment: oxygen electrode (WTW Trioxmatic EO 200) and meter (WTW OXI 530) (Retsch, Ochten, The Netherlands)
- Test performed in closed vessels due to significant volatility of test substance: no, it was a closed system but not because of volatility of the test substance.
- Test performed in open system: no

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Abiotic sterile control: no
- Toxicity control: no
Reference substance:
acetic acid, sodium salt
Parameter:
% degradation (O2 consumption)
Value:
61
Sampling time:
28 d
Remarks on result:
other: test material
Parameter:
% degradation (O2 consumption)
Value:
77
Sampling time:
42 d
Remarks on result:
other: test material
Parameter:
% degradation (O2 consumption)
Value:
72
Sampling time:
28 d
Remarks on result:
other: solvent from test material
Results with reference substance:
At day 14 sodium acetate was degraded 65%.

The chemical oxygen demand (COD) of acetyl acetone peroxide in solvent is 1.6 mg/mg. The COD of the solvent is 2.2 mg/mg. The theoretical oxygen demand of sodium acetate is 0.8 mg/mg.

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
This study is reliable with the above mentioned restrictions. It is performed according to OECD guideline 301D under GLP and all validity criteria were fulfilled.
The calculated endpoints are adequate for C&L and risk assessment purposes
Executive summary:

In order to assess the biotic degradation, a ready biodegradability test was performed which allows the biodegradability to be measured in an aerobic aqueous medium. The ready biodegradability was determined in the Closed Bottle test performed according to slightly modified OECD, EU and ISO Test Guidelines, and in compliance with the OECD principles of Good Laboratory Practice. The test was prolonged because the pass level was not reached at day 28.

 

Acetylacetone peroxide in solvent caused a slight reduction in the endogenous respiration during the first two weeks of the test. The test substance was therefore considered to be non-inhibitory to the inoculum.

 

Acetylacetone peroxide in solvent was biodegraded 61% at day 28 in the Closed Bottle test. In the prolonged Closed Bottle test this compound was biodegraded 77% at day 42. The biodegradation reached at day 28 demonstrated that the test substance is readily biodegradable.

 

The test is valid as is shown by an endogenous respiration of 1.2 mg/L at day 28 and by the total mineralization of the reference compound, sodium acetate. Sodium acetate was degraded 65% of its theoretical oxygen demand after 14 days. Finally, the most important criterion was met by oxygen concentrations >0.5 mg/L in all bottles during the test period.

Description of key information

In order to assess the biotic degradation, a ready biodegradability test was performed which allows the biodegradability to be measured in an aerobic aqueous medium. The ready biodegradability was determined in the Closed Bottle test performed according to slightly modified OECD, EU and ISO Test Guidelines, and in compliance with the OECD principles of Good Laboratory Practice. The test was prolonged because the pass level was not reached at day 28.

 

Acetylacetone peroxide in solvent caused a slight reduction in the endogenous respiration during the first two weeks of the test. The test substance was therefore considered to be non-inhibitory to the inoculum.

 

Acetylacetone peroxide in solvent was biodegraded 61% at day 28 in the Closed Bottle test. In the prolonged Closed Bottle test this compound was biodegraded 77% at day 42. The biodegradation reached at day 28 demonstrated that the test substance is readily biodegradable.

 

The test is valid as is shown by an endogenous respiration of 1.2 mg/L at day 28 and by the total mineralization of the reference compound, sodium acetate. Sodium acetate was degraded 65% of its theoretical oxygen demand after 14 days. Finally, the most important criterion was met by oxygen concentrations >0.5 mg/L in all bottles during the test period.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable
Type of water:
freshwater

Additional information