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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:
20 Feb - 7 Jun 2018
Reliability:
1 (reliable without restriction)

Data source

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

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Deviations:
no
GLP compliance:
yes (incl. QA statement)

Test material

Constituent 1
Chemical structure
Reference substance name:
2-ethylhexyl 12-hydroxyoctadecanoate
EC Number:
249-793-7
EC Name:
2-ethylhexyl 12-hydroxyoctadecanoate
Cas Number:
29710-25-6
Molecular formula:
C26H52O3
IUPAC Name:
2-ethylhexyl 12-hydroxyoctadecanoate
Test material form:
other: oil
Details on test material:
a-ethyl-hexyl-oxystearate
Specific details on test material used for the study:
Batch A9859
DOM July 5 2016
Recertification July 2018

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
sewage, predominantly industrial, adapted
Details on inoculum:
Source The source of test organisms was activated sludge freshly obtained from a municipal sewage treatment plant: 'Waterschap Aa en Maas', 's-Hertogenbosch, The Netherlands, receiving predominantly domestic sewage.
Treatment The freshly obtained sludge was kept under continuous aeration until further treatment. Before use, the sludge was coarsely sieved (1 mm) and washed with mineral medium. After treatment the concentration of suspended solids (SS) was determined to be 3 g/L in the concentrated sludge as used for the test. The magnetically stirred sludge was used as inoculum at the amount of 3 mL per litre of mineral medium, leading to a SS concentration of 8 mg/L.
Duration of test (contact time):
>= 28 d
Initial test substance concentration
Initial conc.:
>= 15.3 mg/L
Based on:
TOC
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
CO2 evolution
Reference substance
Reference substance:
other: silica

Results and discussion

% Degradationopen allclose all
Key result
Parameter:
% degradation (CO2 evolution)
Value:
>= 52
Sampling time:
28 d
Key result
Parameter:
% degradation (CO2 evolution)
Value:
>= 58
Sampling time:
72 h
Details on results:
The relative biodegradation values calculated from the measurements performed during the test period revealed 52% and 58% biodegradation of the test substnace (based on ThCO2), for the duplicate vessels tested. Thus, the criterion for ready biodegradability (at least 60% biodegradation) was not met.
In the silica blank, slightly higher background CO2 production was observed. The test item bottles were compared with the silica blanks.
In the toxicity control, the test substance was found not to inhibit microbial activity.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
inherently biodegradable
Conclusions:
In conclusion, the test substance was not readily biodegradable under the conditions of the modified Sturm test presently performed. However, since the results of the present test indicate that the pass level criterion was almost fulfilled the results can be used to indicate inherent biodegradability.
Executive summary:

The objective of the study was to evaluate the test item test substance for its ready biodegradability in an aerobic aqueous medium with microbial activity introduced by inoculation with activated sludge.

The study procedures described in this report were in compliance with the OECD guideline No. 301 B, 1992. At the request of the Sponsor, the test item was coated on silica particles. Additional blanks were included to correct for the possible effects of using silica.

The test substance was a clear yellowish liquid (UVCB) and was not sufficiently soluble to allow preparation of an aqueous solution at a concentration of 1 g/L. The Total Organic Carbon (TOC) content of the test item was determined to be 78.61%. Based on the TOC content the ThCO2of the test item was calculated to be 2.88 mg CO2/mg. The test item was tested in duplicate at a target concentration of 15.3 mg/L, corresponding to 12 mg TOC/L.

The study consisted of eight bottles:

·        2 inoculum blanks (no test item),

·        2 silica blanks (silica, no test item),

·        2 test bottles (silica, test material),

·        1 procedure control (sodium acetate) and

·        1 toxicity control (silica, test material and sodium acetate).

Aliquots of 34.3 µL were pipetted directly onto weighed amounts of silica in clear glass weighing bottles. After careful mixing, the silica containing the test item was added directly to the 2 litre test bottles containing medium with microbial organisms and mineral components. Subsequently, Milli-RO water was added to each weighing bottle containing the silica in order to quantitatively add all silica to the test medium.The test solutions were continuously stirred during the test, to ensure optimal contact between the test item and the test organisms.Test duration was28 days for the inoculum blank, silica blank, and test item (last CO2measurement on day 29) and 14 days for the procedure and toxicity control (last CO2measurement on day 15).

The relative biodegradation values calculated from the measurements performed during the test period revealed 52% and 58% biodegradation of test material (based on ThCO2), for the duplicate vessels tested. Thus, the criterion for ready biodegradability (at least 60% biodegradation) was not met.

In the silica blank, slightly higher background CO2production was observed. The test item bottles were compared with the silica blanks.

In the toxicity control, the test material was found not to inhibit microbial activity.

Since all criteria for acceptability of the test were met, this study was considered to be valid.

In conclusion, the test material was not readily biodegradable under the conditions of the modified Sturm test presently performed. However, since the results of the present test indicate that the pass level criterion was almost fulfilled the results can be used to indicate inherent biodegradability.[1]


[1]OECD Guidelines For The Testing Of Chemicals. Revised Introduction To The OECD Guidelines For Testing Of Chemicals, Section 3, Part 1, Chapter 2.5, Paragraph 36. (adopted July 23 March 2006).