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Diss Factsheets

Environmental fate & pathways

Biodegradation in water: screening tests

Administrative data

biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
August-September 2018
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference Type:
study report
Report date:

Materials and methods

Test guideline
according to guideline
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
GLP compliance:

Test material

Constituent 1
Chemical structure
Reference substance name:
Sodium [(6-hydroxy-4-methyl-2-oxo-2H-1-benzopyran-7-yl)oxy]acetate
EC Number:
EC Name:
Sodium [(6-hydroxy-4-methyl-2-oxo-2H-1-benzopyran-7-yl)oxy]acetate
Cas Number:
Molecular formula:
sodium [(6-hydroxy-4-methyl-2-oxo-2H-1-benzopyran-7-yl)oxy]acetate
Test material form:
solid: particulate/powder
Details on test material:
Batch 44034
Description: Cream to light grey powder
Expiry date: 30 November 2019
Storage conditions: Controlled room temperature (15-25 ºC, below 70 RH%).

Study design

Oxygen conditions:
Inoculum or test system:
sewage, predominantly domestic, adapted
Details on inoculum:
The inoculum: Secondary effluent, microorganisms from a domestic waste water treatment plant.
Origin: The secondary effluent was supplied from the sewage plant for domestic sewage in Veszprém, Hungary.
Conditioning: The secondary effluent used for this study was allowed to settle approximately for an hour, then the decanted effluent was aerated until use (not later than an hour).
Duration of test (contact time):
28 d
Initial test substance concentration
Initial conc.:
4.4 mg/L
Based on:
1.35 mg O2/mg test item
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
The test was carried out in an incubator and controlled environment room (during the formulation and oxygen measuring) at a temperature of 22 +/- 2 °C according to guideline. The test flasks were placed into an incubator and kept at 20.1 - 23.4°C, in the dark. The temperature was measured on weekdays during the experiment.
The oxygen concentration of test water was 8.6 mg/L at the start of the test.
The pH value of the test water was checked prior start of the experiment. The pH of the test water was 7.23.

The test conditions were measured with suitable instruments and documented in the raw data.
Reference substance
Reference substance:
benzoic acid, sodium salt

Results and discussion

Preliminary study:
14-d preliminary test
Test performance:
The study met the validity criteria.
% Degradation
Key result
% degradation (O2 consumption)
Sampling time:
28 d
Details on results:
Dissolved Oxygen Concentrations at Different Time Intervals during the Exposure Period of 28 Days:
mg O2/L after n days of exposure
0 7 14 21 28
8.20 7.50 7.50 7.50 7.45

BOD at Different Time Intervals during the Exposure Period of 28 Days
Flask BOD after n days of exposure
7 14 21 28
1a 0.14 0.11 -0.01 0.01
1b 0.14 0.11 -0.01 -0.01

Applicant's summary and conclusion

Validity criteria fulfilled:
Interpretation of results:
not readily biodegradable
Under the test conditions the percentage biodegradation of Sodium [(6-hydroxy-4-methyl-2-oxo-2H-1-benzopyran-7-yl)oxy]acetate reached a mean of 0.0 % after 28 days based on the ThOD of the test item. According to the test guidelines the pass level for ready biodegradability is removal of 60 % ThOD.Therefore,the test item is considered not readily biodegradable.
Executive summary:

The test item Sodium [(6-hydroxy-4-methyl-2-oxo-2H-1-benzopyran-7-yl)oxy]acetate was investigated for its ready biodegradability in a Closed Bottle Test over a period of 28 days. The biodegradation was followed by the oxygen uptake of the microorganisms during exposure. As a reference item Sodium benzoate was tested simultaneously under the same conditions as the test item, and functioned as a procedure control.

 The test system was a microbial inoculum of good quality, collected from a sewage plant for domestic sewage. The sludge was allowed to settle and then aerated until use.


The reference item Sodium benzoate was sufficiently degraded to a mean of 76.7 % after 14 days, and to a mean of 81.7 % after 28 days of incubation, based on ThOD, thus confirming the suitability of the used inoculum.


In the toxicity control containing both, the test item and the reference item Sodium benzoate, a mean of 41.4 % biodegradation was noted within 14 days and 43.5 % biodegradation after 28 days of incubation.


According to the test guidelines the test item can be assumed to be not inhibitory at the applied concentration level of4.4 mg/Lon the secondary effluent microorganisms because degradation was >25 % within 14 days.

 The study met the validity criteria. The test item was not considered to have significant inhibitory effects on the secondary effluent microorganisms.Based on the results of this study, the test item is considered not readily biodegradable.