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Diss Factsheets

Environmental fate & pathways

Biodegradation in water: screening tests

Administrative data

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
03-10-2019 - 01-11-2019 (experimental phase)
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2019
Report date:
2019

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Deviations:
yes
Remarks:
see "Principles of method if other than guideline"
Principles of method if other than guideline:
A minor deviation from the guidelines of the Closed Bottle test (OECD TG 301D) was introduced; ammonium chloride was omitted from the medium to prevent oxygen consumption due to nitrification (omission does not result in nitrogen limitation as shown by the biodegradation of the reference compound).
GLP compliance:
yes (incl. QA statement)

Test material

Constituent 1
Chemical structure
Reference substance name:
2,4-Hexadienoic acid, 1,1’-[2-ethyl-2-[[(1-oxo-2,4-hexadien-1-yl)oxy]methyl]-1,3-propanediyl] ester
EC Number:
950-112-7
Cas Number:
347377-00-8
Molecular formula:
C24H32O6
IUPAC Name:
2,4-Hexadienoic acid, 1,1’-[2-ethyl-2-[[(1-oxo-2,4-hexadien-1-yl)oxy]methyl]-1,3-propanediyl] ester

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
other: River water without particles was used as inoculum
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): River water was sampled from the Rhine near Heveadorp, The Netherlands (26-09-2019). The nearest plant (Arnhem-Zuid) treating domestic wastewater biologically was 3 km upstream.
- Preparation of inoculum for exposure: The river water used in the Closed Bottle test was spiked per liter of water with 8.51 mg KH2PO4, 21.75 mg K2HPO4, 33.42 mg Na2HPO4.2H2O, 22.50 mg MgSO4·7H2O, 27.51 mg CaCl2, 0.25 mg FeCl3·6H2O.Ammonium chloride was not added to the river water to prevent nitrification. Sodium acetate was added to the bottles using a stock solution of 1.0 g/L. The test item, a poorly water-soluble substance was administered using a stock solution of 1.0 g/L in dichloromethane.
- Pretreatment: The river water was aerated for 7 days before use to reduce the endogenous respiration (van Ginkel and Stroo, 1992). River water without particles was used as inoculum. The particles were removed by sedimentation after 1 day while moderately aerating.
Duration of test (contact time):
28 d
Initial test substance concentration
Initial conc.:
2 mg/L
Based on:
not specified
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
see "Any other information on materials and methods incl. tables"
Reference substance
Reference substance:
acetic acid, sodium salt

Results and discussion

% Degradation
Parameter:
% degradation (O2 consumption)
Value:
62
Sampling time:
28 d

BOD5 / COD results

Results with reference substance:
The biodegradation percentage of the reference compound, sodium acetate, at day 14 was 83

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The biodegradation in water (screening) was determined in a well-documented guideline study compliant to GLP. Therefore, it can be considered as reliable without restrictions (Reliability 1). According to the results of this study, the test item 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. The test item was biodegraded by 62% at day 28 in the OECD 301D Closed Bottle test. The time window criterion should not be applied as a pass/fail criterion because test sample is a poorly water soluble substance. Test sample is therefore classified as readily biodegradable based on the >60% biodegradation reached at day 28. The test is valid as shown by an endogenous respiration of 0.75 mg/L and by the total mineralization of the reference compound, sodium acetate. Sodium acetate was degraded by 83% 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.
Executive summary:

To assess the biotic degradation of the test sample, 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 310D and in compliance with the OECD principles of GLP.

The test item (2 mg/L) was exposed to river water which was spiked with nutrients, dosed in closed bottles and incubated in the dark at 22.4-22.9°C for 28 days. The degradation of the test item was assessed by the measurement of oxygen consumption. According to the results of this study, the test item 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.

The test item was biodegraded by 62% at day 28 in the OECD 301D Closed Bottle test. The time window criterion should not be applied as a pass/fail criterion because test sample is a poorly water soluble substance. Test sample is therefore classified as readily biodegradable based on the >60% biodegradation reached at day 28.

The test is valid as shown by an endogenous respiration of 0.75 mg/L and by the total mineralization of the reference compound, sodium acetate. Sodium acetate was degraded by 83% 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.