Bis[4-(tert-butyl)benzoato-O]hydroxyaluminium

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:

2018-05-08 - 2018-06-05 (experimental phase)

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Report date:

2018

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

Version / remarks:

OECD Guideline for Testing of Chemicals No. 301 F: "Ready Biodegradability: Manometric Respirometry Test", adopted July 17, 1992

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)

Version / remarks:

Commission Regulation 440/2008/EC, Method C.4-D of May 30, 2008: Manometric Respirometry Test (EEC Publication No. L 142/496, May 2008)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Bis[4-(tert-butyl)benzoato-O]hydroxyaluminium

EC Number:

236-109-7

EC Name:

Bis[4-(tert-butyl)benzoato-O]hydroxyaluminium

Cas Number:

13170-05-3

Molecular formula:

C22H27AlO5

IUPAC Name:

aluminum hydroxide bis(4-tert-butylbenzoate)

Test material form:

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): sewage treatment plant Rossdorf, Germany
- Pretreatment: The aerobic activated sludge used for this study was deposited for 60 min, washed by centrifugation and the supernatant liquid phase was decanted. The solid material was re-suspended in test water and centrifuged again. This procedure was done three times. An aliquot of the final sludge suspension was weighed, dried and the ratio of wet sludge to its dry weight was determined. Based on this ratio, calculated aliquots of washed sludge suspension, corresponding to 3.5 g dry material per litre were mixed with test water and aerated overnight. This suspension was used for the experiment.
- Concentration of sludge: Stock suspension of 3.5 g/L on dry matter base (final sludge concentration in test flasks: 28.7 mg sludge/L)
- Water filtered: no

Duration of test (contact time):

28 d

Initial test substance concentration

Initial test substance concentration 1

Initial conc.:

102.5 mg/L

Based on:

test mat.

Initial test substance concentration 2

Initial conc.:

216 mg/L

Based on:

ThOD

Remarks:

NH4

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium:
Reconstituted test water:
Analytical grade salts were added to pure water to prepare the following stock solutions:
a) 8.5 g KH2PO4, 21.75 g K2HPO4, 33.4 g Na2HPO4 x 2 H2O, 0.5 g NH4Cl filled up with pure water to 1000 mL volume; The pH-value was 7.4.
b) 11.25 g MgSO4 x 7 H2O filled up with pure water to 500 mL volume
c) 18.2 g CaCl2 x 2 H2O filled up with pure water to 500 mL volume
d) 0.125 g FeCl3 x 6 H2O filled up with pure water to 500 mL volume
In order to avoid precipitation of iron hydroxide in the stock solution d), one drop of concentrated HCl per litre was added before storage.
50 mL of stock solution a) and 5 mL of the stock solutions b) to d) were combined and filled up to a final volume of 5000 mL with pure water.
The pH was adjusted to pH 7.4 with NaOH solution.
- Test temperature: 22°C ± 1°C
- pH: 7.5 (measured at the start of the test), 7.2 to 7.6 (measured at the end of the test)
- pH adjusted: yes
- Suspended solids concentration: 28.7 mg sludge/L (final sludge concentration)
- Continuous darkness: yes
- Other: surrounding type: climatised chamber

TEST SYSTEM
- Culturing apparatus: Manometric Test System with test flasks containing a volume of approximately 500 mL. The test flasks were closed gas-tight by a measuring head
- Number of culture flasks/concentration: 2 (test item + inoculumn + test water)
- Measuring equipment: The pressure decrease in the reaction vessels was measured daily over complete experimental phase of 28 days using the BSB/BOD-Sensor-System, Aqualytic Dortmund, Germany.
- Other:
Volume of test vessels: 500 mL
Final volume of test solution: 244 mL

CONTROL AND BLANK SYSTEM
- Inoculum blank: 2 (inoculumn + test water)
- Abiotic sterile control: 1 (test item + CuSO4 (5 mL of a 1 g/L stock solution) + test water)
- Toxicity control: 1 (test item + reference item sodium benzoate + inoculumn + test water)
- Other: Procedure control: 1 (reference item sodium benzoate + inoculumn + test water)

Reference substance

Reference substance:

benzoic acid, sodium salt

Results and discussion

Test performance:

No observations were made which might cause doubts concerning the validity of the study outcome.

% Degradation

Key result

Parameter:

% degradation (O2 consumption)

Value:

73

Sampling time:

28 d

BOD5 / COD results

Results with reference substance:

The percentage degradation of the reference item should reach the level for ready biodegradability (>60%) within 14 days as required by the test guideline.
The reference item sodium benzoate was degraded to more than 60% after 6 days of incubation.
The reference item sodium benzoate was sufficiently degraded to 78% after 14 days and to 81% after 28 days of incubation.
The percentage biodegradation of the reference item confirms the suitability of the used aerobic activated sludge inoculum.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

The study was conducted under GLP according to OECD TG301F and EU method C.4E on the registered substance itself without deviations from the guideline or deficiencies in documentation. The method is considered reasonable, the reference substance produced the appropriate response and the validity criteria are met. Hence, the results can be considered as reliable to assess the ready biodegradability of bis[4-(tert-butyl)benzoato-O]hydroxyaluminium with highest quality (Klimish 1).
The degradation rate of bis[4-(tert-butyl)benzoato-O]hydroxyaluminium did not reach 60% within the 10-day window, but after 28 days. Accordingly, bis[4-(tert-butyl)benzoato-O]hydroxyaluminium is considered to be readily biodegradable, but failing 10-day window. However, as the degradation rate was determined to be 58% (57% Flask 1 and 59% Flask 2) at the end of the 10-day window and was 61% (61% Flask 1 and 60% Flask 2) 24 hours later, the criteria of the 10-day window were regarded as fullfilled and bis[4-(tert-butyl)benzoato-O]hydroxyaluminium was considered readily biodegradable for further assessments.

Executive summary:

The biodegradability of the test substance was investigated under GLP according to EU method C.4 -D and OECD guideline 301 F in a manometric respirometry test over a period of 28 days. The biodegradation was followed by the oxygen uptake of the microorganisms during exposure. As a reference item sodium benzoate was tested simultaneously under the same conditions as the test item, and functioned as a procedure control. A measured volume of inoculated mineral medium, containing the test item in a concentration of 102.5 mg/L (corresponding to a ThOD_NH4of 216.0 mg/L), was stirred in a closed flask at a constant temperature for up to 28 days. Aerobic activated sludge from a domestic wastewater treatment plant was used as inoculum. Analytical grade salts were added to deionised water to prepare the stock solutions. Sodium benzoate was used as reference item (positive control). Also a toxicity control (test item and reference item mixed) was run in parallel, to ensure, that the chosen test concentration was not inhibitory to the aerobic activated sludge microorganisms. The degradation rate of the test item was calculated by the oxygen consumption of the aerobic activated sludge microorganisms after 28 days of incubation.

 

The criterion for ready biodegradability under the conditions of a manometric respirometry test is the degradation of the test item of at least 60%, reached within a 10-day window; the 10-day window starts when the degradation of the test item reaches at least 10% degradation.

The mean biodegradation of 10% or higher of bis[4-(tert-butyl)benzoato-O]hydroxyaluminium was reached at day 7 (ThOD_NH4), when the degradation was 15%. At the end of the 10-day window at day 17, the mean degradation of bis[4-(tert-butyl)benzoato-O]hydroxyaluminium was 58% (ThOD_NH4) and therefore the 10 day window criterion was not passed. The mean biodegradation at test end after 28 days was 73% (ThOD_NH4).

Therefore, bis[4-(tert-butyl)benzoato-O] hydroxyaluminium is considered to be readily biodegradable based on ThOD_NH4, but failing 10-day window.

 

The reference item sodium benzoate was sufficiently degraded to 78% after 14 days and to 81% after 28 days of incubation, thus confirming the suitability of the aerobic activated sludge inoculum used

 

In the toxicity control containing both, the test item and the reference item sodium benzoate, 44% (ThOD_NH4) biodegradation was noted within 14 days and 61% (ThOD_NH4) biodegradation after 28 days of incubation. According to the test guidelines, the test item can be assumed to be not inhibitory to the aerobic activated sludge microorganisms because degradation was >25% within 14 days

 

No observations were made which might cause doubts concerning the validity of the study outcome.

 

The result of the test can be considered valid.