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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:
2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
The reliability rating is a 1 because the study followed an OECD standard guideline, which describes a procedure designed to evaluate this endpoint, and the results were reviewed for reliability and assessed as valid. The study was also conducted under GLP.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2017
Report Date:
2017

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
no
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
liquid: viscous

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
Fresh activated sludge was used as the inoculum. The activated sludge was obtained from a domestic wastewater treatment facility in New Jersey, USA. This treatment facility was selected because it deals predominantly with domestic sewage as specified in the guideline. There were no known contaminants in the fresh activated sludge believed to be present at levels high enough to interfere with this study. Fresh activated sludge was obtained on day -1 of the test. The activated sludge was homogenized in a blender for two minutes at medium speed. The homogenated sample was allowed to settle for approximately 30 minutes, after which the supernatant was decanted (avoiding carry-over of sludge solids). An aliquot of the supernatant was used to determine microbial activity. The microbial activity was determined using an Easicult®-TTC dip slide. The agar stick was removed from the culturing tube and the agar dipped into the supernatant aliquot. Excess supernatant was blotted off with a clean paper towel, and the agar stick was then placed back into the culture tube. The whole unit was placed into an environmental chamber for 24 hours at approximately 21 degrees C. The remaining decanted sludge supernatant was used for final preparation of the test medium on day -1.
Duration of test (contact time):
28 d
Initial test substance concentration
Initial conc.:
ca. 34 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
Biodegradation was based on oxygen consumption and the theoretical oxygen demand of the test substance as calculated using results of an elemental analysis of the test substance. The empirical formula and the theoretical oxygen demand (ThOD) of the test substance were calculated from elemental analysis data (assuming 100 gram test substance). Sodium benzoate ThOD was calculated using the empirical formula and was determined to be 1.66 mg O2/mg sodium benzoate. The ThOD calculation of the test and positive control substance was based on the OECD 301F guideline.The microbial count of the activated sludge was 10E4 CFU/mL. The sludge supernatant was added at a 1% loading volume to test medium. Test medium consisted of glass distilled water and mineral salts (phosphate buffer, ferric chloride, magnesium sulfate, calcium chloride). Test medium and activated sludge, which was aerated for 24 hours with carbon dioxide free air, was added to each respirometer flask.Test vessels were glass flasks placed in a water bath and electronically monitored for oxygen consumption. Triplicate test systems were run for the test substance; the positive control and the blanks.Test substance concentration was~50 mg/L. Test temperature was 21 – 23 deg C.All test vessels were stirred constantly for 28 days using magnetic stir bars.
Reference substance
Reference substance:
benzoic acid, sodium salt

Results and discussion

Test performance:
No deviations from the protocol were noted. By day 3, >60% biodegradation of positive control was observed, which meets the guideline requirement.
% Degradationopen allclose all
Parameter:
% degradation (O2 consumption)
Value:
23.7
St. dev.:
6.85
Sampling time:
10 d
Remarks on result:
other: Based on ThOD
Parameter:
% degradation (O2 consumption)
Value:
42.83
St. dev.:
4.73
Sampling time:
20 d
Remarks on result:
other: Based on ThOD
Parameter:
% degradation (O2 consumption)
Value:
47.58
St. dev.:
2.46
Sampling time:
28 d
Remarks on result:
other: Based on ThOD
Parameter:
% degradation (O2 consumption)
Value:
93.19
St. dev.:
1.43
Sampling time:
22 d
Remarks on result:
other: Based onThOD of dilithium glutarate
Parameter:
% degradation (O2 consumption)
Value:
93.85
St. dev.:
1.91
Sampling time:
28 d
Remarks on result:
other: Based on ThOD
Details on results:
Test material was not readily biodegradable. By day 28, 47.6% degradation of the test material was observed.

BOD5 / COD results

Results with reference substance:
Sodium benzoate biodegraded 67% after 4 days (range 60.8 to 63.0), and 89% in 28 days.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
The test substance is not readily biodegradable in an OECD 301F Manometric Respirometry test.
Executive summary:

The test substance is not readily biodegradable in an OECD 301F Manometric Respirometry test.