Registration Dossier

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
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2018

Materials and methods

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

Test material

Constituent 1
Reference substance name:
Avena Sativa leaf/stem extract
EC Number:
948-064-7
IUPAC Name:
Avena Sativa leaf/stem extract
Specific details on test material used for the study:
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).

Study design

Inoculum or test system:
sewage, domestic (adaptation not specified)
Duration of test (contact time):
28 d
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.

Results and discussion

% Degradation
Key result
Parameter:
% degradation (O2 consumption)
Value:
66.8
Sampling time:
28 d

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
inherently biodegradable
Conclusions:
According to the test guidelines the test item can be assumed to be not inhibitory at the applied concentration level of 7.3 mg/L on 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 readily biodegradable.
Executive summary:

The Test Item 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.

Under the test conditions the percentage biodegradation ofthe Test Item reached a mean of 66.8 % after 28 days based on the COD of the test item.According to the test guidelines the pass level for ready biodegradability, 60 % of ThOD/COD and this level has to be reached in a 10-day window within the 28-day period of the test. However taking into account that the test item was sufficiently degraded to a mean of 62.6 % after 14 days and according to the test guideline the value obtained in a 14-day window would also be acceptable in the used method, therefore the test item is considered readily biodegradable.

 

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 46.9 % biodegradation was noted within 14 days and 48.0 % 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 of 7.3 mg/L on 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 readily biodegradable.