4-acetyl-2-methylbenzoic acid

Biodegradation in water: screening tests

Administrative data

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2020

Report date:

2020

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

1992

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

4-acetyl-2-methylbenzoic acid

EC Number:

856-079-4

Cas Number:

55860-35-0

Molecular formula:

C10H10O3

IUPAC Name:

4-acetyl-2-methylbenzoic acid

Test material form:

solid: particulate/powder

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

Fresh sample of activated sewage sludge taken on 24 April 2020 from STP Ruhrverband Kläranlage, 57392 Schmallenberg, Germany mainly treating domestic wastewater.
Sample was filtered (2 mm) to remove coarse particles and washed once with tap water. The sludge sample was kept aerobic after arrival in the laboratory until use. The sludge was left for settlement for circa one hour. The supernatant was discarded and the concentration of suspended solids was measured in the remaining sludge. The concentration was adjusted to 3.9 g/L in tap water, which was verified by dry mass measurement.
The concentration used in the test was 29.6 mg of sludge (dry mass) per litre, corresponding to 7.4 mg dry mass per 250 mL.

Duration of test (contact time):

28 d

Initial test substance concentration

Initial conc.:

28 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

Stock solutions for mineral medium were prepared by dissolving the following minerals (analytical grade) in deionised water:
Stock solution a) KH2PO4 at 8.51 g/L, K2HPO4 at 21.76 g/L, Na2HPO4 at 26.64 g/L, NH4Cl at 0.50 g/L
Stock solution b) CaCl2.2H2O at 36.40 g/L
Stock solution c) MgSO4.7H2O at 22.50 g/L
Stock solution d) FeCl3.6H2O at 0.25 g/L
The mineral medium used in the test was prepared with 10 mL/L of stock solution a) and 1 mL/L of the stock solutions b)-d), diluted with deionised water free from toxic substances (e.g. Cu2+ ions). Organic carbon content was checked at regular intervals by dissolved organic carbon analysis, which was found to be 0.16 mg/L in the last analysis before medium preparation. This corresponds to 0.9% of the organic carbon introduced by the test substance, which is clearly less than the value of 10% deemed acceptable according to the test guideline.
The test substance was tested at a concentration of 28 mg/L, corresponding to 53.3 mg O2/L theoretical oxygen demand. No emulsifier or solvent was used. The reference substance sodium benzoate was tested at a concentration of 100 mg/L. A toxicity control was run in parallel containing the test substance at 28 mg/L and the reference substance at 100 mg/L. Furthermore, inoculum controls and abiotic controls were run. All the tests were performed with two test replicates in parallel under the same conditions.
Before the start of the test, the pH values of all solutions were determined and adjusted to 7.4 ± 0.2 with H2SO4.

Reference substance

Reference substance:

benzoic acid, sodium salt

Results and discussion

% Degradation

Parameter:

% degradation (O2 consumption)

Value:

15.1

St. dev.:

3.9

Sampling time:

28 d

BOD5 / COD results

Results with reference substance:

The reference substance was degraded on average by 88% by day 14, confirming the suitability of the activated sewage sludge used in the system. At the end of the test, biodegradation of the test substance was 92%.

Any other information on results incl. tables

The pH values of all test solutions ranged 7.2 to 7.3 at the begin of the test. The pH values of the test solutions ranged from 7.2 to 7.6 at the end of the test.

The biodegradation in the toxicity control reached 72% within 14 days, showing that the test substance was not inhibitory at the test concentration of 28 mg/L. 

The average cumulative oxygen consumption in the inoculum blank was 26.5 mg O2/L after 28 days.

The manometric respirometry test met the validity criteria of the guidance, since 

- the difference of extremes of replicate values was 6%, which is less than 20%

- the reference substance degraded by more than 60% by day 14

- the cumulative oxygen uptake of the inoculum blank was <60 mg/L within 28 days

- the pH values measured in the test flasks were within the acceptable range from 6.0 to 8.5

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

An average biodegradation of the test substance of 15.1% was observed over a period of 28 days.

Executive summary:

The ready biodegradability of the substance was studied under GLP to OECD TG 301F in a manometric respiratory test using non-adapted aerobic activated sewage sludge from a public STP treating predominantly domestic wastewater. All test vessels were incubated at 22 °C under continuous stirring in the dark over a period of 28 days. All studies were performed with standard mineral medium prepared from stock solutions. The concentration of the sewage sludge was 29.6 mg dry mass/L. The concentration of the test substance was 28 mg/L, and the reference substance sodium benzoate was tested at 100 mg/L. A toxicity control containing the test substance at 28 mg/L and the reference substance at 100 mg/L was also tested. An inoculum control and an abiotic control was also run. All tests were conducted with two replicates in parallel under the same conditions. The test met all the validity criteria of the guidance, demonstrating the suitability of the sewage sludge used in the study. The average biodegradation of the test substance reached 15.1% after 28 days. The substance showed to be not readily biodegradable under the applied test conditions.