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Environmental fate & pathways

Biodegradation in water: screening tests

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Administrative data

Endpoint:
biodegradation in water: inherent biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2010-02-12 to 2010-05-19
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Guideline-conform study under GLP without deviations.

Data source

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

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 302 C (Inherent Biodegradability: Modified MITI Test (II))
Deviations:
no
Principles of method if other than guideline:
The following modifications were made: activated sludge from one source was used, the activated sludge was not fed during the holding period of maximum seven days, the test was run at 22 °C, the test water composition was slightly changed, and only the biological oxygen demand (BOD) was monitored, no test item specific analysis was performed.
GLP compliance:
yes (incl. certificate)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Tert-butyl-4-methoxy-4'-dibenzoylmethane
- Substance type: organic mono constituent
- Physical state: solid

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): aerobic activated sludge from a wastewater treatment plant (ARA Ergolz II, Füllinsdorf, Switzerland)
- Laboratory culture: not applicable
- Method of cultivation: not applicable
- Storage conditions: During the holding period the sludge was aerated at room temperature.
- Storage length: three days prior to use
- Preparation of inoculum for exposure: Prior to use, the sludge was first thoroughly mixed and then diluted with test water to a concentration of 1 g per liter (dry weight basis). Based on the determined dry weight of this diluted activated sludge, defined amounts were added to test water to obtain a final concentration of 100 mg dry material per liter.
- Pretreatment: not applicable
- Concentration of sludge: 100 mg dry material per liter
- Initial cell/biomass concentration: 100 mg dry material per liter
- Water filtered: no
Duration of test (contact time):
28 d
Initial test substance concentration
Initial conc.:
30 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: The test water was prepared according to the OECD Guideline for Testing of Chemicals No. 301 F, Ready Biodegradability: Manometric Respirometry Test, 1992. Analytical grade salts were dissolved in purified water (detailed compositions of stock solutions and final media described in the study report)
- Additional substrate: none
- Solubilising agent (type and concentration if used): none
- Test temperature: 22 °C
- pH: The pH measured in all flasks at the start of the test was 7.4. At the end of exposure (Day 28), pH values of 7.2 to 7.8 were measured.
- pH adjusted: yes
- CEC (meq/100 g): no data
- Aeration of dilution water: no data
- Suspended solids concentration: 100 mg dry material per liter
- Continuous darkness: yes
- Other:

TEST SYSTEM
- Culturing apparatus: SAPROMAT D12 (Voith GmbH, Heidenheim, Germany)
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: stirring
- Measuring equipment: The biodegradation process consumes the dissolved oxygen in the test medium and generates CO2. The CO2 is adsorbed by soda lime, which results in a decrease of the total pressure in the airtight test flasks. The pressure drop is detected and converted into an electrical signal by means of an electrode type manometer. The consumed oxygen is replaced by electrolytically generated oxygen from a copper sulfate solution.
- Test performed in closed vessels due to significant volatility of test substance: substance not volatile, still closed vessels used
- Test performed in open system: no
- Details of trap for CO2 and volatile organics if used: basket for soda lime particles inside the airspace of the reaction vessels
- Other:

SAMPLING
- Sampling frequency: Oxygen consumption was recorded by taking a daily reading at least on each working day.
- Sampling method: manually


CONTROL AND BLANK SYSTEM
- Inoculum blank: activated sludge, no test item, no reference item
- Abiotic sterile control: none performed
- Toxicity control: activated sludge, test item plus reference item
- Other: Procedure control: activated sludge, no test item, with reference item

STATISTICAL METHODS: no statistics applied
Reference substance
Reference substance:
benzoic acid, sodium salt

Results and discussion

Preliminary study:
In previous studies, the test item was not readily biodegradable nor anaerobically biodegradable.
Test performance:
In the procedure controls, the reference item was degraded by an average of 74% and 83% by Exposure Day 7 and 14, respectively, thus confirming suitability of the activated sludge. At the end of the test (Day 28), the reference item was degraded by an average of 95%.
% Degradation
Parameter:
% degradation (O2 consumption)
Value:
4
Sampling time:
28 d
Remarks on result:
other: average of two samples
Details on results:
The percent biodegradation of the test item was calculated based on the theoretical oxygen demand (ThOD) of 2.47 mg O2/mg test item. The biochemical oxygen demand (BOD) of the test item in the test media was in the normal range found for the inoculum controls throughout the study period of 28 days. Consequently, Tert-butyl-4-methoxy-4'-dibenzoylmethane was not biodegradable under the test conditions within 28 days.
In the toxicity control, containing both Tert-butyl-4-methoxy-4'-dibenzoylmethane and the reference item sodium benzoate, Tert-butyl-4-methoxy-4'-dibenzoylmethane had no inhibitory effect on the activity of activated sludge microorganisms at the tested concentration of 30 mg/L.

BOD5 / COD results

BOD5 / COD
Parameter:
BOD5
Value:
ca. 133 mg O2/g test mat.
Results with reference substance:
The percent biodegradation of the reference item sodium benzoate was calculated based on the theoretical oxygen demand of 1.67 mg O2/mg. In the procedure controls, the reference item was degraded by an average of 74% and 83% by Exposure Day 7 and 14, respectively, thus confirming suitability of the activated sludge. At the end of the test (Day 28), the reference item was degraded by an average of 95%.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Remarks:
Procedure controls and toxicity controls are valid.
Interpretation of results:
not inherently biodegradable
Conclusions:
Test item Tert-butyl-4-methoxy-4'-dibenzoylmethane was not inherently biodegradable under the test conditions within 28 days.
Executive summary:

The test item Tert-butyl-4-methoxy-4'-dibenzoylmethane was investigated for its inherent biodegradability in a manometric respirometry test over 28 days based on the OECD Guideline for Testing of Chemicals No 302 C (1981). The biochemical oxygen demand (BOD) of the test item in the test media was in the normal range found for the inoculum controls. Consequently, the test item Tert-butyl-4-methoxy-4'-dibenzoylmethane was not biodegradable under the test conditions within 28 days. In the toxicity control, containing both Tert-butyl-4-methoxy-4'-dibenzoylmethane and the reference item sodium benzoate, Tert-butyl-4-methoxy-4'-dibenzoylmethane had no inhibitory effect on the activity of activated sludge microorganisms at the tested concentration of 30 mg/L. In the procedure controls, the reference item (sodium benzoate) was degraded by an average of 74% and 83% by Exposure Days 7 and 14, respectively, thus confirming suitability of the activated sludge. At the end of the test (Day 28), the reference item was degraded by an average of 95%.