Registration Dossier

Environmental fate & pathways

Biodegradation in water: screening tests

Currently viewing:

Administrative data

Link to relevant study record(s)

Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Specific details on test material used for the study:
Batch/Lot number: 10000005282
Purity: 99.4%
Appearance: powder
Solubility in water: insoluble in water
Storage: at ambient temperature in the dark
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, non-adapted
Details on inoculum:
Secondary activated sludge (09-02-2017) was obtained from the wastewater treatment plant Nieuwgraaf in Duiven, The Netherlands. This plant is an activated sludge plant treating predominantly domestic wastewater. The activated sludge was preconditioned to reduce the endogenous respiration rates. To this end, 0.40 g Dry Weight (DW)/L of activated sludge was aerated for one week. The sludge was diluted in the bottles to 2.0 mg/L (van Ginkel and Stroo, 1992). The inoculum was not pre-adapted to the test substance.
Duration of test (contact time):
28 d
Initial conc.:
2 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
The Closed Bottle test was performed according to the study plan. The study plan was developed from ISO Test Guidelines (1994). Use was made of 10 bottles with test substance and inoculum, 10 bottles treated with DCM (added and evaporated) with inoculum, 10 bottles only containing inoculum and 6 bottles with sodium acetate and inoculum.
The concentrations of the test substance, and sodium acetate in the bottles were 2.0 and 6.7 mg/L, respectively. Each of the prepared solutions was dispensed into the respective group of BOD bottles so that all bottles were completely filled without air bubbles. The zero time bottles were immediately analyzed for dissolved oxygen using an oxygen electrode. The remaining bottles were closed and incubated in the dark. Two duplicate bottles of all series were withdrawn for analyses of the dissolved oxygen concentration at day 7, 14, 21, and 28.
Reference substance:
acetic acid, sodium salt
Key result
Parameter:
% degradation (O2 consumption)
Value:
81
Sampling time:
28 d
Details on results:
Ethylene glycol dibenzoate was biodegraded by 81% at day 28 in the Closed Bottle test. Over 60% biodegradation was achieved in a period of approximately 5 days immediately following the attainment of 10% biodegradation at day 1. Ethylene
glycol dibenzoate therefore fulfilled the 14-day time window (10-day time window for other OECD 301 tests) criterion for ready biodegradable compounds.
Results with reference substance:
The biodegradation percentage of the reference compound, sodium acetate, at day 14 was 80.

Theoretical oxygen demand (ThOD)

The calculated theoretical oxygen demand (ThOD) of ethylene glycol dibenzoate is 2.1 g oxygen/g test substance. The ThOD of sodium acetate is 0.8 mg/mg.

Toxicity

Inhibition of the degradation of a well-degradable compound, e.g. sodium acetate by the test substance in the Closed Bottle test was not determined because possible toxicity of ethylene glycol dibenzoate to microorganisms degrading acetate is not relevant. Inhibition of the endogenous respiration of the inoculum by the test substance at day 7 was not detected. Therefore, no inhibition of the biodegradation due to the "high" initial test substance concentration is expected.

Test conditions

The pH of the media was 7.3 at the start of the test. The pH of the media at day 28 was 7.3 (test, control (DCM added and evaporated), standard control). Temperatures were within the prescribed temperature range of 22 to 24°C.

Validity of the test

The validity of the test is demonstrated by an endogenous respiration of 0.8 mg/L at day 28. Furthermore, the differences of the replicate values at day 28 were less than 20%.

The biodegradation percentage of the reference compound, sodium acetate, at day 14 was 80. Finally, the validity of the test is shown by oxygen concentrations >0.5 mg/L in all bottles during the test period.

Oxygen consumption (mg/L) and the percentages biodegradation of the test substance (BOD/ThOD) and sodium acetate (BOD/ThOD) in the Closed Bottle test.

Time (days)

Oxygen consumption (mg/L)

Biodegradation (%)

 

Test substance

Acetate

Test substance

Acetate

0

0.0

0.0

0

0

7

3.1

4.1

74

76

14

3.3

4.3

79

80

21

3.3

 

79

 

28

3.4

 

81

 

 

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
Ethylene glycol dibenzoate should be classified as readily biodegradable.
Executive summary:

In order to assess the biotic degradation of ethylene glycol dibenzoate, 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.

Ethylene glycol dibenzoate did not cause a reduction in the endogenous respiration at day 7.

The test substance is therefore considered to be non-inhibitory to the inoculum. Ethylene glycol dibenzoate was biodegraded by 81% at day 28 in the OECD 301 Closed Bottle test.

Over 60% biodegradation was achieved in a period of approximately 5 days immediately following the attainment of 10% biodegradation thereby fulfilling the time window criterion for ready biodegradable substances. The substance should therefore be classified as readily biodegradable.

The test is valid as shown by an endogenous respiration of 0.8 mg/L and by the complete degradation of the reference compound, sodium acetate. Sodium acetate was degraded by 80% 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

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.

Ethylene glycol dibenzoate did not cause a reduction in the endogenous respiration at day 7.

The test substance is therefore considered to be non-inhibitory to the inoculum. Ethylene glycol dibenzoate was biodegraded by 81% at day 28 in the OECD 301 Closed Bottle test.

Over 60% biodegradation was achieved in a period of approximately 5 days immediately following the attainment of 10% biodegradation thereby fulfilling the time window criterion for ready biodegradable substances. The substance should therefore be classified as readily biodegradable.

The test is valid as shown by an endogenous respiration of 0.8 mg/L and by the complete degradation of the reference compound, sodium acetate. Sodium acetate was degraded by 80% 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

Additional information