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Environmental fate & pathways

Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2001-10-08 to 2002-03-12
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
no
Remarks:
The testing facility indicated that the protocol was followed without deviation
Qualifier:
according to
Guideline:
EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)
Deviations:
no
Remarks:
The testing facility indicated that the protocol was followed without deviation
GLP compliance:
yes
Remarks:
The Federal Office of Public Health, the Swiss Agency for the Environment, Forests and Landscape and the Intercantonal Office for the Control of Medicines with respect to the compliance with the Swiss legislation on Good Laboratory Practice.
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: activated sludge from a wastewater treatment plant (ARA Ergolz II, Fϋllinsdorf, Switzerland) treating predominantly domestic wastewater
- Laboratory culture: not applicable
- Method of cultivation: no data
- Storage conditions: at room temperature with aeration until use
- Storage length: no data
- Preparation of inoculum for exposure: The sludge was washed once with tap water by centrifugation and the supernatant liquid phase was decanted. A homogenized aliquot of the final sludge suspension was weighed, thereafter dried and the ratio of wet to dry weight was calculated. Based on this ratio, calculated amounts of wet sludge were suspended in test water to obtain a concentration equivalent to 4 g (±10%) dry material per liter. During holding, the sludge was aerated at room temperature until use. Prior to use, the sludge was diluted with test water to a concentration of 1 g per liter (dry weight basis). This diluted activated sludge was used as inoculum to give a final concentration of 30 mg dry material per liter
- Pretreatment: no data
- Concentration of sludge: 1 g per liter (dry weight basis)
- Initial cell/biomass concentration: no data
- Water filtered: no
- Type and size of filter used, if any: not applicable
Duration of test (contact time):
28 d
Initial conc.:
105 mg/L
Based on:
test mat.
Initial conc.:
103 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: the test medium was preapered according to the testing guidelines
- Additional substrate: no
- Solubilising agent: not applicable
- Test temperature: 22 deg C, maintained with a built-in thermostat and checked once per week
- pH: The pH was in the range of 7.3 - 7.4 prior to test start measured in each test flask after the addition of the activated sludge inoculum. At the end of incubation (28 days) the pH was measured again in each test flask and found to be in the range of 7.3 – 7.5.
- pH adjusted: no
- CEC (meq/100 g): no data
- Aeration of dilution water: no data
- Suspended solids concentration: 30 mg dry material per liter
- Continuous darkness: yes
- Other: The test water was prepared according to the testing guidelines. No emulsifiers or solvents were used but ultrasound dispersion was employed for fifteen minutes to dissolve the test item completely. The test flasks were incubated under continuous stirring. For the dosage of the reference item, a stock solution containing 250 mg sodium benzoate per 100 mL test water was prepared. From this 10 mL aliquots were added to the corresponding test flasks. To each flask (with the exception of the abiotic control) activated sludge was added and all flasks were made up to a volume of 250 mL with test water.


TEST SYSTEM
- Culturing apparatus: 500 mL Erlenmeyer flasks
- Number of culture flasks/concentration: 2 (105 and 103 mg/L)
- Method used to create aerobic conditions: The consumed oxygen is replaced by electrolytically generated oxygen from a copper sulfate solution.
- Method used to create anaerobic conditions: not applicable
- Measuring equipment: The biodegradation process consumes the dissolved oxygen in the liquid and generates CO2. The CO2 is adsorbed by soda lime and the total pressure decreases in the airtight test flasks. The pressure drop is detected and converted into an electrical signal by means of an electrode type manometer.
- Test performed in closed vessels due to significant volatility of test substance: no
- Test performed in open system: no
- Details of trap for CO2 and volatile organics if used: The CO2 is adsorbed by soda lime.
- Other: no data


SAMPLING
- Sampling frequency: continious measurement
- Sampling method: not applicable
- Sterility check if applicable: not applicable
- Sample storage before analysis: not applicable
- Other: not applicable


CONTROL AND BLANK SYSTEM
- Inoculum blank: flasks 1 and 2 without test substance or reference substance
- Abiotic sterile control: flask 5 containing 100 mg/L of the test substance poisoned with mercury dichloride at a concentrationof 10 mg/L
- Toxicity control: flask 7 containing 105 mg/L of test substance and 100 mg/L of the reference substance (sodium benzoate).
- Other: two procedure controls with 100 mg/L reference substance


STATISTICAL METHODS:
no data
Reference substance:
benzoic acid, sodium salt
Test performance:
No circumstances that may have affected the results occurred during the test
Parameter:
% degradation (O2 consumption)
Value:
-2
Sampling time:
28 d
Remarks on result:
other: The percent biodegradation of the test item was calculated based on the theoretical oxygen demand of 1.45 mg 02/mg test item without nitrification (ThOD NH4)
Parameter:
% degradation (O2 consumption)
Value:
-2
Sampling time:
28 d
Remarks on result:
other: The percent biodegradation of the test item was calculated based on the theoretical oxygen demand of 1.61 mg 02/mg test item with nitrification (ThOD NO3)
Details on results:
The biochemical oxygen demand of the test substance in the test media was within the range of the inoculum controls. T002102 was found to be not biodegradable under the test conditions within 28 days.
Results with reference substance:
The percent biodegradation of the reference item, sodium benzoate, was determined to be 89% based on theoretical oxygen demand after 28 days. The reference item was degraded by an average of 85% by exposure Day 14, thus confirming suitability of the activated sludge.
Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
T002102 was found to be not biodegradable under the test conditions within 28 days.

Description of key information

In the guideline study (Piether, 2002) the test substance, T002102, did not biodegrade under the test conditions within 28 days. Hence, it is concluded to be non biodegradable. Results of this study are reliable without restrictions.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed
Type of water:
freshwater

Additional information