Trimethylacetic anhydride

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:

2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Qualifier:

equivalent or similar to guideline

Guideline:

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

Deviations:

not applicable

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

TEST ORGANISM:
- mixed population of aquatic microorganisms, origin from an aeration tank of a waste water plant treating predominantly domestic sewage (Wupper area water authority, WWTP Odenthal, Germany)
- concentration: 30 mg/L suspendid solids

PRETREATMENT OF THE INOCULUM:
- Before use, the inoculum was stored for two days at room temperature under continuous stirring with aeration
- The sludge was washed twice by adding mineral medium and centrifuging for 10 min at 2000 rpm and 20 °C and decanting off the supernatant
- An aliquot of the wet sludge was dried in order to determine the wet weight/dry weight ratio of the sludge and to prepare a stock suspension (activated sludge) of 3 g dw/L
- The calculated amount of sludge, needed to achieve 300 mL of this stock suspension, was dissolved in mineral medium and then filled up to a defined end volume

Duration of test (contact time):

28 d

Initial conc.:

100 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

PRETREATMENT OF THE TEST ITEM/REFERENCE SUBSTANCE:
- 25 mg of the test item were weighed out and added to the test flasks, filled with 200 mL of mineral medium
- the volume was made up to 250 mL with mineral medium containing the inoculum to give a test concentration of 100 mg reference compound /L

PRETREATMENT OF THE TOXICITY CONTROL:
- 25 mg of the test item and 25 mg of the reference compound were weighed out and added to the test flasks, filled with 200 mL of mineral medium
- Afterwards the flask volume was made up to 250 mL with mineral medium containing the inoculum to give a test concentration of 100 mg test item and reference compound/L

EXPOSURE CONDITION:
- Test volume: 250 ml
- Incubation temperature: 22 +/- 1 °C
- Performed in the dark
- Mixing: 1 magnetic stirrer per test vessel
- Test apparatus: OxiTopControl System (WTW)

Reference substance:

benzoic acid, sodium salt

Remarks:

Acros Organics (Purity: 99.9 %; Batch number: A0357641)

Parameter:

% degradation (O2 consumption)

Value:

0

Sampling time:

7 d

Parameter:

% degradation (O2 consumption)

Value:

18

Sampling time:

14 d

Parameter:

% degradation (O2 consumption)

Value:

53

Sampling time:

21 d

Key result

Parameter:

% degradation (O2 consumption)

Value:

64

Sampling time:

28 d

Parameter:

% degradation (O2 consumption)

Value:

1

Sampling time:

9 d

Results with reference substance:

The reference compound showed 86% degradation after 14 days and the theoretical oxygen demand was 1.665 mg O2/mg

Valdity criteria:

- The reference compound has reached the level of higher than 60 % for ready biodegradability within 14 days

- The toxicity control exhibited degradation rates > 25 % within 14 days

- At the end of the test, at the plateau, or the end of the 10-d window, biodegradation in parallels with test item did not differ by more than 20 percentage points

- The oxygen uptake of the inoculum blank was < 60 mg/L

- In cases where the degradation was < 60 %, the pH values were in between 6.0 and 8.5 at the end of the test

Validity criteria fulfilled:

yes

Remarks:

(see "Any other information on results incl. tables")

Interpretation of results:

readily biodegradable, but failing 10-day window

Conclusions:

In the study on ready biodegradability a degradation rate of 64 % was determined within 28 days for the substance. Nevertheless, 10 days after the start of degradation at day 9 only 43 % of the test substance were degraded at day 19. Therefore the substance is readily biodegradable, but failing the 10-day window.

Executive summary:

The study was conducted in accordance with the Council Directive 92/69/EEC Method C.4-D "Manometrie Respirometry Test". This test method is in assential parts identical with OECD Guideline 301 F. A solution of the substance in a mineral medium was inoculated and incubated for 28 d under aerobic conditions. During this period the ready biodegradability was determined. The substance showed 64 % degradation after 28 days. 10 days after the start of degradation at day 9 43 % degradation were observed at day 19. The reference compound showed 86% degradation after 14 days.

Description of key information

In the study on ready biodegradability a degradation rate of 64 % was determined within 28 days for the substance. After 10 days only 3 % degradation was observed.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable but failing 10-day window

Additional information

The substance showed 64 % biodegradation after 28 days, but only 43 % at day 19, 10 days after the start of the degradation process at day 9. Therefore the substance is readily biodegradable, but failing the 10-day window.