Aluminium tribenzoate

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

29 Mar 2017 - 28 Apr 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Version / remarks:

1992

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: ISO International Standard 10634. "Water Quality - Guidance for the preparation and treatment of poorly water-soluble organic compounds for the subsequent evaluation of their biodegradability in an aqueous medium"

Version / remarks:

1995

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

3 November 2015

Specific details on test material used for the study:

Since Aluminium tribenzoate was not sufficiently soluble to allow preparation of an aqueous solution at a concentration of 1 g/L, weighed amounts were added to the 2-litres test bottles containing medium with microbial organisms and mineral components (test item bottle A: 37.10 mg; test item bottle B: 37.07 mg and toxicity control bottle: 37.09 mg). To this end, 10 mL of Milli-RO water was added to each weighing bottle containing the test item. After vigorous mixing (vortex) the resulting suspension was added quantitatively to the test medium. The test solutions were continuously stirred during the test, to ensure optimal contact between the test item and the test organisms. Furthermore, the test medium was daily swirled around since the test item tended to float on the water surface.
No correction for purity was made.

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: Activated sludge was freshly obtained from a municipal sewage treatment plant: 'Waterschap Aa en Maas', 's-Hertogenbosch, The Netherlands, receiving predominantly domestic sewage.

- Preparation of inoculum for exposure: The freshly obtained sludge was used immediately. The concentration of suspended solids was determined to be 3.6 g/L in the concentrated sludge. Before use, the sludge was allowed to settle (31 minutes) and the supernatant liquid was used as inoculum at the amount of 10 mL/L of mineral medium.

- Pretreatment: The day before the start of the test (day -1) mineral components, Milli-RO water (ca. 80% of final volume) and inoculum (1% of final volume) were added to each bottle. This mixture was aerated with synthetic air overnight to purge the system of CO2.

Duration of test (contact time):

28 d

Initial conc.:

19 mg/L

Based on:

test mat.

Initial conc.:

12 mg/L

Based on:

TOC

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: According to OECD 301B
- Test temperature: 22.2-23.7 °C
- pH: at t=0h: 7.5, at t=14d: 7.8, at t=28d:7.4-7.5
- pH adjusted: no
- Continuous darkness: yes, the test media were excluded from light and the test vessels were brown coloured glass bottles.

TEST SYSTEM
- Number of culture flasks/concentration: 2 for test suspension, 2 for inoculum blank, 1 for positive control and 1 for toxicity control.
- Method used to create aerobic conditions: sparging with CO2-free synthetic air (CO2<1 ppm). A mixture of oxygen (ca. 20%) and nitrogen (ca. 80%) was passed through a bottle, containing 0.5 - 1 litre 0.0125 M Ba(OH)2 solution to trap CO2 which might be present in small amounts. The synthetic air was sparged through the scrubbing solutions at a rate of approximately 1-2 bubbles per second (ca. 30-100 mL/min).
- Details of trap for CO2 and volatile organics: Three CO2-absorbers (bottles filled with 100 mL 0.0125 M Ba(OH)2) were connected in series to the exit air line of each test bottle.

SAMPLING
- Sampling frequency: Titrations were made every second or third day during the first 10 days, and thereafter at least every fifth day until day 28, for the inoculum blank and test suspension. Titrations for the positive and toxicity control were made over a period of at least 14 days.
- Sampling method: Titration of Ba(OH)2 in the gas scrubbing bottles.


CONTROL AND BLANK SYSTEM
- Inoculum blank: Yes; contained only inoculum (2 bottles)
- Abiotic sterile control: No
- Toxicity control: Yes; contained test item, reference item, and inoculum (1 bottle)
- Other: positive control; contained reference item and inoculum.

Reference substance:

acetic acid, sodium salt

Key result

Parameter:

% degradation (CO2 evolution)

Value:

90

Sampling time:

28 d

Remarks on result:

other: Mean of 2 test bottles

Details on results:

- Biodegradation: Biodegradation at the end of the experiment was 79% for Bottle A and 101% for Bottle B, giving a mean biodegradation of 90%. The difference between Bottle A and Bottle B was >20% at the end of the test, but <20% at the 10-day window, thereby meeting the acceptability criteria. Bottle B reached at least 60% biodegradation within a 10-day window. Since the titrations only started on day 4, it is not clear whether Bottle A also met this limit within the 10-day window. However, from the graph it is seen that Bottle A was meeting the 60% biodegradation around day 13, so it is considered acceptable that also bottle A met the 10-day window.
- Toxicity control: In the toxicity control, >25% biodegradation occurred within 14 days. Therefore, the test item was assumed not to inhibit microbial activity.
- ThCO2 production: The ThCO2 of Aluminium tribenzoate was calculated to be 2.07 mg CO2/mg. The ThCO2 of sodium acetate was calculated to be 1.07 mg CO2/mg.

For a short period (<1 day) there was no aeration, which was considered by the Test Facility to have no impact on the outcome and the overall integrity of the study, or the interpretation of the study results and conclusions.

Results with reference substance:

The positive control, sodium acetate, showed a normal biodegradation curve and reached 85% biodegradation after 14 days, which passes the validity criterium of at least 60% biodegradation within 14 days.

Validity criteria

1. The positive control item was biodegraded by at least 60% (85%) within 14 days.

2. The difference of duplicate values for %-degradation of the test item until attainment of 60% biodegradation within a 10-day window was less than 20 (≤ 11%).

3. The total CO2 release in the blank at the end of the test did not exceed 40 mg/L (47.8 mg CO2 per 2 litres of medium, corresponding to 23.9 mg CO2/L).

4. The Inorganic Carbon content (IC) of the test item (suspension) in the mineral medium at the beginning of the test was less than 5% of the Total Carbon content (TC). Since the test medium was prepared in tap-water purified by reverse osmosis (Milli-RO water (Millipore Corp., Bedford, Mass., USA, carbon levels < 500 ppb)), IC was less than 5% of TC (mainly coming from the test item, 12 mg TOC/L).

Since all criteria for acceptability of the test were met, this study was considered to be valid.

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

The relative biodegradation values calculated from the measurements performed during the test period revealed 79% and 101% biodegradation of Aluminium tribenzoate, for A and B, respectively (based on ThCO2).
The 60% biodegradation was obtained within the 10-day window for bottle B and in approximation also in bottle A. Aluminium tribenzoate was considered readily biodegradable under the conditions of the modified Sturm test presently performed.

Executive summary:

The 'ready' biodegradability of Aluminium tribenzoate was investigated in the Carbon Dioxide (CO2) Evolution Test (Modified Sturm Test), according to OECD Guideline 301 B and GLP principles. A test concentration of 19 mg/L test item, corresponding to 12 mg TOC/L. Based on the results, biodegradation of Aluminium tribenzoate was 79% and 101% in two replicates. The 60% biodegradation was obtained within the 10-day window for bottle B and in approximation also in bottle A. Therefore, aluminum tribenzoate is considered readily biodegradable.

The test met all criteria for acceptability, and thus is considered reliable without restrictions.

Description of key information

For Aluminium tribenzoate, the ready biodegradability was determined in a study according to OECD TG 301B (Ready Biodegradability: CO2 Evolution, Modified Sturm Test) and in compliance with GLP criteria. In this study 19 mg/L test substance (12 mg/L based on TOC) was inoculated with fresh activated sludge from a biological waste water treatment plant treating predominantly domestic sewage for 28 days. After 28 days, 79 -101% biodegradation was observed. The 60% biodegradation was obtained within the 10-day window for bottle B and in approximation also in bottle A. Thus, the substance is concluded to be readily biodegradable. The test met all validity criteria and is considered valid.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater