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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:
2009-11-13 to 2009-12-14
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Study conducted in compliance with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results. The study report was conclusive and done to a valid guideline.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2010
Report date:
2010

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)
Deviations:
no
GLP compliance:
yes (incl. QA statement)

Test material

Constituent 1
Chemical structure
Reference substance name:
5-Bromo-1H-pyrrolo[2,3-b]pyridine
EC Number:
629-247-8
Cas Number:
183208-35-7
Molecular formula:
C7H5BrN2
IUPAC Name:
5-Bromo-1H-pyrrolo[2,3-b]pyridine
Test material form:
other: solid
Details on test material:
Purity >99%

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
Not adapted activated sludge from the aeration tank of the ARA Werdhölzli (CH-8048 Zürich), a municipal biological waste water treatment plant. 30 mg/l dry matter in the final mixture.
Duration of test (contact time):
28 d
Initial test substance concentration
Initial conc.:
58.5 mg/L
Based on:
ThOD/L
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
other: DOC concentration
Details on study design:
The activated sludge was used after sampling from the treatment plant without adaptation. However, the sludge was pre-conditioned for 3 days (aerated but not fed) to reduce the amount of O2 consumed by the blank controls.
Prior to the test the sludge was washed twice with tap water. After centrifugation the sludge, at a concentration twice of the final concentration to be achieved for the test, was suspended in test medium. The test material was applied by direct addition to give the final test concentration of about 58.7 mg/L. This refers to a ThOD value of about 100 mg O2/L.
The reference material was dissolved in the test medium at a concentration twice of the final concentration to be achieved for the test. An appropriate amount of this stock solution was diluted with the sludge suspension to give a final test concentration as ThOD of about 80-100 mg O2/L (i.e. about 50 mg/L reference substance).
In the toxicity control about 53.7 mg/L test substance and about 50 mg/l reference substance were tested as a mixture.
For each test series the following number of test flasks was set up:
T: Test suspension containing inoculum, test medium and test substance (two replicates)
B: Inoculum blank containing inoculum and test medium (two replicates)
R: Procedure control containing inoculum, test medium and sodium benzoate as ready biodegradable reference compound (two replicates)
C: Abiotic sterile control: containing test substance, ultra pure water and 0.2 mM HgCl2 as sterilizing agent to prevent microbial decomposition
X: Toxicity control: containing inoculum + test medium + test substance + sodium benzoate as ready biodegradable reference compound

The test vessels were stirred by an inductive stirring system for a maximum test period of 28 days. During the test the O2 uptake was continuously measured with a manometric BOD measuring device. The pH-value was checked at the beginning and at the end of the test. The value at the beginning was adjusted to pH 7.2 (± 0.2) with NaOH or HCl, respectively.
The biodegradation of the test material was followed by daily measurements. Additionally, ultimate biodegradation was determined based on theoretical carbon content and the analyses of dissolved organic carbon (DOC) concentrations at the end of the test.
Reference substance
Reference substance:
benzoic acid, sodium salt

Results and discussion

Details on results:
Based on the data of the individual O2 determinations, no biodegradability in the Manometric Respirometry Test of the test item was observed after 28 days. The respective DOC concentrations at the beginning and at the end of the test after 28 days were (in mg/l):
25.0 and 23.4 for the test units (mean of two replicates)
<0.5 and <0.5 for the inoculum blank (mean of two replicates)
29.2 and 0.51 for the procedure control (mean of two replicates)
1) theoretical concentration based on molecular formula
The calculated elimination based on DOC measurement reached 7% for the Test Substance and 100% for sodium benzoate. The data show that the test substance will not be retained in sewage treatment plants.
The test substance did not reach the pass level of 60% for ready biodegradability in the Manometric Respirometry Test within the 10-d window as well as after 28 days and, therefore, cannot be termed as readily biodegradable in the sense of the OECD guideline 301

BOD5 / COD results

Results with reference substance:
The positive control, sodium benzoate, reached 86% biodegradation after 14 days, thus confirming suitability of inoculum and test conditions.

Any other information on results incl. tables

At the applied initial test concentration of 58.0 mg/L the test substance showed no significant toxic effect on the microbial population, since the biodegradation of the mixture (test substance + reference compound sodium benzoate) was within the expected theoretical value during the whole test period. The test was considered valid, since more than 25% degradation occurred within 14 days.

The test substance was not abiotically degraded (by processes using O2) during the whole test period of 28 days in the absence of microorganisms as confirmed by the lack of oxygen consumption.

At the end of the test the pH value of both inoculum blanks and the procedure control was 7.2 and 7.3, respectively. The pH values of the test units and both controls were 7.3, 7.5 and 7.1, respectively.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
The test substance was not biodegradable in the Manometric Respirometry Test.
Executive summary:

Method: The biodegradability of the test substance exposed to microorganisms derived from activated sludge of a municipal sewage treatment plant was investigated under aerobic static exposure conditions. The activated sludge was used after sampling from the treatment plant without adaptation. The test vessels were stirred by an inductive stirring system for a maximum test period of 28 days. During the test the O2 uptake was continuously measured with a manometric BOD measuring device.

Results: No biodegradability of the test substance based on O2 consumption was observed during 28 days as compared to the theoretical oxygen demand (ThOD). The procedure control sodium benzoate reached 86% biodegradation after 14 days, thus confirming suitability of inoculum and test conditions. At the applied initial test concentration of 58.0 mg/L the test substance showed no significant toxic effect on the microbial population, since the biodegradation of the mixture (test substance + reference compound sodium benzoate) was within the expected theoretical value during the whole test period. The test was considered valid, since more than 25% degradation of the reference substance still occurred within 14 days. The test substance was not abiotically degraded (by processes using O2) during the whole test period of 28 days in the absence of microorganisms as confirmed by the lack of oxygen consumption. The calculated elimination based on DOC measurement reached 7% for the test substance and 100% for sodium benzoate. The data show that the test substance will not be retained in sewage treatment plants.

Conclusion: The test substance did not reach the pass level of 60% for ready biodegradability in the Manometric Respirometry Test within the 10-d window as well as after 28 days and, therefore, cannot be termed as readily biodegradable in the sense of the OECD guideline 301.

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