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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
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 F (Ready Biodegradability: Manometric Respirometry Test)
GLP compliance:
yes (incl. QA statement)

Test material

Constituent 1
Chemical structure
Reference substance name:
Ethyl lactate
EC Number:
EC Name:
Ethyl lactate
Cas Number:
Molecular formula:
ethyl 2-hydroxypropanoate
Test material form:
colorless transparent liquid

Study design

Oxygen conditions:
Inoculum or test system:
activated sludge, domestic, adapted
Details on inoculum:
Activated sludge from a biologic sewage treatment plant was used. The chosen plant is treating mostly household sewage.
The sludge was taken from the activation basin of the ESN (Stadtentsorgung Neustadt) sewage treatment plant, Im Altenschemel, NW-Lachen-Speyerdorf.
Date of collection: 25. Oct. 2017, batch no: 20171025.
The sludge was filtrated, washed with medium 2x, then resuspended in test medium. It was then aerated.
The dry matter was determined as 4560 mg suspended solids/L.
Duration of test (contact time):
ca. 28 d
Initial test substance concentration
Initial conc.:
ca. 62 mg/L
Based on:
Reference substance
Reference substance:
benzoic acid, sodium salt

Results and discussion

% Degradation
% degradation (O2 consumption)
ca. 70
Sampling time:
28 d
Details on results:
10-day-window: day 2 – 12
degradation at the end of 10-day-window 61 %
degradation at the end of the test 70 %

Any other information on results incl. tables

All validity criteria were met.

Oxygen consumption in the blank controls and in the positive controls was normal, indicating that the test system has worked properly.

As a plateau of degradation was reached it is considerable, that the maximal degradation of the test item due to the test conditions was reached.

The ThOD of the test item was calculated and based on molecular formula of the test item, given by the sponsor. The 10-day-window began on day 2 (this is stated as lag phase), at its end (day 12), 61 % were reached, surpassing the pass level of 60 % given in the OECD guideline.

As a plateau of degradation was reached it is considerable, that the maximal degradation of the test item due to the test conditions was reached.

Therefore, when applying the 10-day-window, the test itemEthyl lactateis considered as readily biodegradable following OECD 301F/EU C.4-D.

No observations were made which might cause doubts concerning the validity of the study outcome.

The result of the test can be considered valid.

Applicant's summary and conclusion

Validity criteria fulfilled:
Interpretation of results:
readily biodegradable
When applying the 10-day-window, Ethyl lactate is classified as readily biodegradable following OECD 301F/EU C.4-D.