Disodium 2-oxoglutarate

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:

29 March - 27 April 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2017

Report date:

2017

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

2006

Deviations:

yes

Remarks:

pH values of the test units and toxicity control were not in the required range at the end of the test. Since biodegradation was calculated to be >60% after 28 days and since the test item proved to be readily biodegradable, the test was considered valid.

Test guideline 2

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

Regulation (EC) No 440/2008

Deviations:

yes

Remarks:

pH values of the test units and toxicity control were not in the required range at the end of the test. Since biodegradation was calculated to be >60% after 28 days and since the test item proved to be readily biodegradable, the test was considered valid.

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Disodium 2-oxoglutarate

EC Number:

206-167-8

EC Name:

Disodium 2-oxoglutarate

Cas Number:

305-72-6

Molecular formula:

C5H6O5.2Na

IUPAC Name:

disodium 2-oxopentanedioate

impurity 1

Reference substance name:

Water

EC Number:

231-791-2

EC Name:

Water

Cas Number:

7732-18-5

Molecular formula:

H2O

IUPAC Name:

Oxidane

Test material form:

solid: crystalline

Remarks:

Crystalline powder

Details on test material:

Batch No: 14152300
Storage: 15 – 25 °C

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source: Sludge from the aeration tank of the ARA Werdhölzli (CH-8048 Zürich), a municipal biological waste water treatment plant.
- Preparation of inoculum for exposure: The sludge was pre-conditioned for 6 days (aerated but not fed) to reduce the amount of O2 consumed by the blank controls. Therefore, the sludge was washed twice with tap water and once with test medium.
- Pretreatment: The activated sludge was used after sampling from the treatment plant without adaptation.
- Concentration of sludge: 30 mg/L dry matter in the final mixture.

Duration of test (contact time):

28 d

Initial test substance concentration

Initial conc.:

151 mg/L

Based on:

other: nominal test item concentration based on 101 mg ThOD/L

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of test medium: Aerobic mineral salts medium prepared with ultrapure water (conductivity: <1.5 µS/cm; DOC: <0.5 mg/L)
* mineral stock solution A (10mL/L): 8.5 g/L KH2PO4, 28.49 g/L K2HPO4.3H2O, 33.4 g/L Na2HPO4.2H2O, 0.5 g/L NH4Cl, pH 7.4
* mineral stock solution B (1 mL/L): 36.4 g/L CaCl2.2H2O
* mineral stock solution C (1 mL/L): 22.5 g/L MgSO4.7H2O
* mineral stock solution D (1 mL/L): 0.25 g/L FeCl3.6H2O
* Final test medium: 10 mL of solution A and 1 mL of solutions B, C and D per L of test medium

- Test temperature: 22±2°C, controlled at ± 1°C, in a thermostat cabinet in the dark
- pH: 7.4±0.2°C (measured prior to testing and if necessary adjusted with NaOH or HCl (except in flask C).
- Continuous darkness: yes, test bottles were in a thermostat cabinet.

TEST SYSTEM
- Test flasks: 510 mL glass bottles (tightly closed with manometric BOD measuring devices) containing a total volume of test solution of 200 mL. The bottles were equipped with stirring rods and butyl rubber quivers which contain 2 pellets of sodium hydroxide each to absorb the produced CO2 from the head space.
- Test performed in duplicate (two test flasks)

After centrifugation, the sludge was suspended in test medium, at about 2 g/L dry matter. Before the test, this suspension was diluted down to 60 mg/L dry matter, i.e. twice the final concentration, since this suspension was diluted 1:1 (v:v) afterwards. The test item was dissolved in the test medium at a concentration twice of the final concentration to be achieved for the test. This stock solution was diluted with the sludge suspension 1:1 (v:v) to give a final test concentration of about 100 mg ThOD/l.

CONTROL AND BLANK SYSTEM
B: Inoculum blank (two replicates)
R: Procedure control (two replicates): 60.1 mg/L Sodium benzoate (100 mg ThOD/L)
C: Abiotic sterile control (one replicate): 153.0 mg/L test item (103 mg ThOD/L)
X: Toxicity control (one replicate): 149 mg/L test item and 60.1 mg/L Sodium benzoate (total 200 mg oxygen demand/L)

SAMPLING
The test vessels were stirred by an inductive stirring system for a maximum test period of 28 days. During the test the O2 uptake was continuously measured with a manometric BOD measuring device. Temperature was recorded with a data logger.
At the end of the test, the pH was measured in all flasks except the abiotic sterile control (C).
Total elimination was determined in each test vessel (test suspension, blank and procedure control) based on the theoretical carbon content and the analysis of the dissolved organic carbon (DOC) concentrations at the end of the test.

STATISTICAL METHODS:
Values of % degradation were calculated for each test flask and day. The arithmetic mean of % degradation in each test flask on each day was calculated.

Reference substance

Reference substance:

other: Sodium benzoate

Remarks:

CAS 532-32-1

Results and discussion

% Degradation

Key result

Parameter:

% degradation (O2 consumption)

Value:

84

Sampling time:

28 d

Remarks on result:

other: test flask 1 after 28 d: 88.9% test flask 2 after 28 d: 78.0%

Details on results:

The biodegradability of alpha-Ketoglutarate disodium salt based on O2 consumption was calculated to be 84% after 28 days as compared to the theoretical oxygen demand (ThOD).
The biodegradation reached 75% at the end of the 10-d window.
Biodegradation of the test item was observed after a lag-phase of about 1 day.
The procedure control sodium benzoate reached 83% biodegradation after 14 days, thus confirming suitability of inoculum and test conditions.

The respective concentrations of organic carbon at the beginning (theoretical value based on the test item’s carbon content and the test concentration, as mg TOC/L) and at the end of the test (mean measured value of the two replicates, as mg DOC/L) were, respectively:
- test units: 47.6 (theoretical value calculated based on the carbon content and the test concentration) and 1.35 (mean of two replicates)
- blank control: <0.5 and 1.61 (mean of two replicates)
- procedure control: 35.0 (theoretical value calculated based on the carbon content and the test concentration) and 1.65 (mean of two replicates)

The total elimination calculated based on dissolved organic carbon (DOC) measurements reached 101% for a -Ketoglutarate disodium salt and 100% for sodium benzoate, respectively. These data confirm the high biodegradability of the test item.

Any other information on results incl. tables

Procedure control:

The procedure control sodium benzoate reached 83% biodegradation after 14 days, thus confirming suitability of inoculum and test conditions.

Toxicity control:

At the applied initial test concentration of 149 mg/L the test item was not judged to have any inhibitory effect on the microbial population, since the biodegradation of the mixture (test item + reference item sodium benzoate) exceeded 25% within 14 days.

Abiotic steril control:

alpha-Ketoglutarate disodium salt was not abiotically degraded (by processes using O2) during the whole test period of 28 days in the absence of microorganisms as confirmed by the lack of significant oxygen consumption.

Remark on pH values:

At the end of the test the pH values of the two blank controls were 7.6 and 7.5, respectively, and the procedure control was 7.6. The pH values of the test units and the toxicity control were 9.0, 9.1 and 8.9, respectively.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Remarks:

pH values of the test units and toxicity control were not in the required range at the end of the test. Since biodegradation was calculated to be >60% after 28 days and since the test item proved to be readily biodegradable, the test was considered valid.

Interpretation of results:

readily biodegradable

Conclusions:

A 28-d ready biodegradability test (OECD 301F, Manometric Respirometry Test) using activated sludge of a municipal sewage treatment plant indicated that alpha-Ketoglutarate disodium salt (CAS no. 305-72-6) reached the pass level of 60% for ready biodegradability in the Manometric Respirometry Test within the 10-d window and, therefore, can be termed as readily biodegradable.

Executive summary:

The biodegradability of alpha-Ketoglutarate disodium salt (CAS no. 305-72-6) exposed to microorganisms derived from activated sludge of a municipal sewage treatment plant was investigated under aerobic static exposure conditions, following the test guideline OECD 301 F.

The biodegradability of alpha-Ketoglutarate disodium salt based on O2 consumption was calculated to be 84% after 28 days as compared to the theoretical oxygen demand (ThOD).

The biodegradation reached 75% at the end of the 10-d window (i.e. within 10 days after attainment of 10% degradation).

Biodegradation of the test item was observed after a lag-phase of about 1 day.

The procedure control sodium benzoate reached 83% biodegradation after 14 days, thusconfirming suitability of inoculum and test conditions.

The total elimination calculated based on dissolved organic carbon (DOC) measurements reached 101% for alpha-Ketoglutarate disodium salt and 100% for sodium benzoate, respectively. This data is in line with the data of oxygen consumption.

alpha-Ketoglutarate disodium salt (CAS no. 305-72-6) reached the pass level of 60% for ready biodegradability in the Manometric Respirometry Test within the 10-d window and, therefore, can be termed as readily biodegradable.

All validity criteria, apart from the pH criterion, were fulfilled. The test was considered valid.