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Environmental fate & pathways

Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Study initiation date - 27 May 2003; Experiment start date - 02 June 2003; Experiment end date - 01 July 2003; Study completion date - 09 July 2003.
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 A (Ready Biodegradability: DOC Die Away Test)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method C.4-A (Determination of the "Ready" Biodegradability - Dissolved Organic Carbon (DOC) Die-Away Test)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Specific details on test material used for the study:
Identity: FAT 40812/A
Batch: WP 8/03
Purity: approx 75 %
Appearance: Solid, dark red-brownish powder
Expiration date: 23 April 2010
Storage: At room temperature at about 20 °C
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, non-adapted
Details on inoculum:
Mixture of polyvalent bacteria (activated sludge) collected on June 02, 2003 from the aeration tank of a domestic sewage treatment plant, ARA Pro Rheno Basel communal. The activated sludge was washed 4 times with tap water and the last time with test medium. A sample of the activated sludge was taken to determine the dry weight of the Suspended Solids (SS). An amount corresponding to 2 - 3 g per liter of suspended solids was mixed with test medium. The pre-treated sludge was aerated until use. The pH value of the activated sludge was 6.8. A bacteria concentration of 26 mg/L suspended solids was obtained by adding 5 mL of the pre-treated sludge (2.6 g/L SS) per 500 mL test medium.
Duration of test (contact time):
28 d
Initial conc.:
36.6 mg/L
Based on:
DOC
Parameter followed for biodegradation estimation:
DOC removal
Details on study design:
For each test series the following number of test vessels was set up:
- Test item: 2 vessels with inoculum + test medium + test item
- Inoculum control: 2 vessels with inoculum + test medium
- Procedure control: 2 vessels with inoculum + test medium + a readily biodegradable reference compound
- Abiotic sterile control: 1 vessel with test medium + test item without inoculum, sterilised by ultra-filtration (Gemlam Vacucap 0.2 µm, sterilised)
- Inhibition control: 1 vessel with inoculum + test medium + test item + reference compound

A measured volume of inoculated mineral medium, containing a known concentration of the test item as the nominal source of organic carbon, was aerated in the dark or diffuse light at 22 ± 2 °C nominal in 500 mL conical vessels containing 200 mL test medium. The degradation was followed by DOC analysis at frequent intervals over a period of 28 days. The degree of biodegradation was calculated by expressing the concentration of DOC removed (corrected by the blank inoculum control) as a percentage of the concentration initially added.
Reference substance:
other: D(+)-Glucose anhydrous
Parameter:
% degradation (DOC removal)
Value:
2
Sampling time:
28 d
Results with reference substance:
Procedure control Biodegradation after 14 days was found to be 95 %

- Inhibition control: 50 % biodegradation after 14 days (and hence not inhibitory on substrate biodegradation).


- Abiotic control: 8 % biodegradation after 28 days.

Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
The test substance was not biodegradable after 28 days of incubation.
Executive summary:

In a GLP-compliant readily biodegradability test, performed according to OECD Guideline 301A, a mixture of polyvalent bacteria (activated sludge obtained from a communal wastewater treatment plant) was exposed to the test substance (36.6 mg/L DOC) for 28 days. The design was a static test at 19.0 - 22.0 °C, test volume 200 mL, continuously shaken, in darkness. 2 % biodegradation was observed for the test substance. 95 % biodegradation was observed with the reference substance D(+)-glucose) after 28 days of incubation. In conclusion, the test substance is not ready biodegradable.

Endpoint:
biodegradation in water: inherent biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Study initiation date - 27 May 2003; Experiment start date - 02 June 2003; Experiment end date - 02 July 2003; Study completion date - 15 July 2003.
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 302 B (Inherent biodegradability: Zahn-Wellens/EMPA Test)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method C.9 (Biodegradation: Zahn-Wellens Test)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Specific details on test material used for the study:
Identity: FAT 40812/A
Batch: WP 8/03
Purity: approx. 75 %
Appearance: Solid, dark red-brownish powder
Expiration date: 23 April 2010
Storage: At room temperature at about 20 °C
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, adapted
Details on inoculum:
Mixture of polyvalent bacteria (activated sludge) collected on June 02, 2003 from the aeration tank of a domestic sewage treatment plant, ARA Pro Rheno Basel communal. The activated sludge was washed twice with tap water one day before the test was started. A sample of the activated sludge was taken to determine the dry weight of the Suspended Solids (SS). The pre-treated sludge was aerated until use. Bacteria concentration was 0.52 g/L suspended solids. The bacteria concentration was obtained by adding 93 mL of the pre-treated sludge (10.8 g/L SS) per 2 liters test medium.
Duration of test (contact time):
28 d
Initial conc.:
153.6 mg/L
Based on:
DOC
Initial conc.:
154.5 mg/L
Based on:
DOC
Parameter followed for biodegradation estimation:
DOC removal
Details on study design:
A mixture of a total test volume of 2 liters each containing test item, mineral medium and activated sludge was agitated and aerated at 20 - 25 °C in two glass vessels in the dark for 28 days. A reference control running in duplicate containing activated sludge, mineral medium and the reference item, and a blank control containing activated sludge and mineral medium were run under the same test conditions. The biodegradation process was monitored by determination of the dissolved organic carbon concentrations (DOC). The ratio of eliminated DOC, corrected for the blank after each time interval, to the initial DOC value was expressed as the percentage biodegradation at each sampling time.
Reference substance:
diethylene glycol
Parameter:
% degradation (DOC removal)
Value:
10
Sampling time:
28 d
Details on results:
- Adsorption of FAT 40812/A after 3 hours: 1 %
- Biodegradation of FAT 40812/A after 28 days: 10 %
- Total elimination of FAT 40812/A after 28 days (regarding adsorption and biodegradation): 11 %
Results with reference substance:
Biodegradation of the reference item after 19 days was found to be 100 %.
Validity criteria fulfilled:
yes
Interpretation of results:
not inherently biodegradable
Conclusions:
Under the conditions of the test 10 % biodegradation was observed.
Executive summary:

In a GLP-compliant inherent biodegradability test (Zahn-Wellens Test / EMPA-Test), performed according to OECD Guideline 302 B, a mixture of polyvalent bacteria (activated sludge obtained from a communal wastewater treatment plant) was exposed for 28 days to the test substance at a test concentration of 153.6 and 154.5 mg/L DOC. Based on the findings of the study, 1 % absorption was observed after 3 hours and 10 % biodegradation was observed after 28 days. The reference item diethylene glycol was completely degraded within the first 19 days of exposure, thus confirming the suitability of the activated sludge.

Description of key information

Both the ready biodegradability test and inherently biodegradability test as well the BOD5/COD quotient indicate that the test substance is not biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
not biodegradable
Type of water:
freshwater

Additional information

Inherent biodegradation:


In a GLP-compliant inherent biodegradability test (Zahn-Wellens Test / EMPA-Test), performed according to OECD Guideline 302 B, a mixture of polyvalent bacteria (activated sludge obtained from a communal wastewater treatment plant) was exposed for 28 days to the test substance at a test concentration of 153.6 and 154.5 mg/L DOC. Based on the findings of the study, 1 % absorption was observed after 3 hours and 10 % biodegradation was observed after 28 days. The reference item diethylene glycol was completely degraded within the first 19 days of exposure, thus confirming the suitability of the activated sludge.


 


Readily biodegradable 301A:


In a GLP-compliant readily biodegradability test, performed according to OECD Guideline 301A, a mixture of polyvalent bacteria (activated sludge obtained from a communal wastewater treatment plant) was exposed to the test substance (36.6 mg/L DOC) for 28 days. The design was a static test at 19.0 - 22.0 °C, test volume 200 mL, continuously shaken, in darkness. 2 % biodegradation was observed for the test substance. 95 % biodegradation was found with reference substance D(+)-glucose) after 28 days of incubation. In conclusion, the test substance is not ready biodegradable.


 


BOD : COD ratio


The BOD5 of the test substance was 0 mg/g oxygen. In another study, the COD was calculated to 838 mg/g oxygen. The resultant BOD : COD ratio was found to be 0 indicating the test substance to be not biodegradable.