Imidazolium compounds, 2-C4-8-alkyl-1-(2-carboxyethyl)-4,5-dihydro-3-(hydroxyethyl), hydroxides, sodium salts

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 June - 27 July

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

2006

Deviations:

yes

Remarks:

see remark in "principles of method if other than guideline"

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:

see remark in "principles of method if other than guideline"

Principles of method if other than guideline:

Deviations from the study plan and/or the guideline:
The temperature deviated from the recommended range (in °C: Maximum: 24.8; Minimum: 22.7; Mean: 23.6; Delta Mean - Max.: 1.2; Delta Mean - Min.: 0.9).
While the slight deviation on the temperature regulation (± 1.2°C instead of ± 1°C) is potentially relevant since it directly influences the measured BOD values, it does not have a significant influence on the calculated degradation, since all tests flasks were exposed to the same conditions (i.e. also the blanks, whose BODC values are subtracted from the test suspensions vessels for the calculation of the biodegradation rates).
The influence of the deviation from the required maximum temperature could have, if any, a positive influence on the biodegradation, since biological processes would have been enhanced. However, since the calculated biodegradation is far from the 60% pass level, this deviation also does not have any significant influence on the outcome of the test

GLP compliance:

yes (incl. QA statement)

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 7 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 conc.:

43.2 mg/L

Based on:

other: nominal test item concentration based on 100.2 mg COD/L

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, T and X).
- 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 COD/l.

CONTROL AND BLANK SYSTEM
B: Inoculum blank (two replicates)
R: Procedure control (two replicates): 60.0 mg/L Sodium benzoate (99.9 mg ThOD/L)
C: Abiotic sterile control (one replicate): 42.5 mg/L test item (98.6 mg COD/L)
X: Toxicity control (one replicate): 43.5 mg/L test item and 60.0 mg/L reference item (total 200.8 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:

other: Sodium benzoate

Remarks:

CAS 532-32-1

Key result

Parameter:

% degradation (O2 consumption)

Value:

20

Sampling time:

28 d

Remarks on result:

other: test flask 1 after 28 d: 18.5% test flask 2 after 28 d: 20.6%

Details on results:

The biodegradability Imidazolium compounds, 2-C4-8-alkyl-1-(2-carboxyethyl)-4,5-dihydro-3-(hydroxyethyl), hydroxides, sodium salts based on O2 consumption was calculated to be 20% after 28 days as compared to the chemical oxygen demand (COD).
The biodegradation reached 14% at the end of the 10-d window (i.e. within 10 days after attainment of 10% degradation). Biodegradation of the test item started without any significant lag-phase.

The respective concentrations of organic carbon at the beginning (as mg DOC/L ; measured in the stock solution) and at the end of the test (mean measured value of the two replicates) were, respectively:
26.3 and 20.4 for the test units (mean of two replicates);
<0.5 and 0.75 for the blank control (mean of two replicates);
35.9 and 0.86 for the procedure control (mean of two replicates).

The total elimination calculated based on dissolved organic carbon (DOC) measurements reached 24% for Imidazolium compounds, 2-C4-8-alkyl-1-(2-carboxyethyl)-4,5-dihydro-3-(hydroxyethyl), hydroxides, sodium salts and 100% for sodium benzoate, respectively. The data is in line with the degradation calculated based on O2 consumption.

Procedure control:

The procedure control sodium benzoate reached 85% biodegradation after 14 days, thus confirming suitability of inoculum and test conditions.

Toxicity control:

At the applied initial test concentration of 43.5 mg/L the test item was not judged to have any inhibitory effecton the microbial population, since the biodegradation of the mixture (test item + reference item sodium benzoate) exceeded 25% within 14 days.

Abiotic steril control:

Imidazolium compounds, 2-C4-8-alkyl-1-(2-carboxyethyl)-4,5-dihydro-3-(hydroxyethyl), hydroxides, sodium salts 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 oxygen consumption.

Validity criteria fulfilled:

yes

Interpretation of results:

not 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 Imidazolium compounds, 2-C4-8-alkyl-1-(2-carboxyethyl)-4,5-dihydro-3-(hydroxyethyl), hydroxides, sodium salts (CAS no. 70983-43-6) reached a biodegradation of 20% based on O2 consumption. The substance did not reach the pass level of 60% for ready biodegradability in the Manometric Respirometry Test neither within the 10-d window nor after 28 days of incubation and, therefore, cannot be termed as readily biodegradable.

Executive summary:

The biodegradability of Imidazolium compounds, 2 -C4 -8 -alkyl-1 -(2 -carboxyethyl)-4,5 -dihydro-3 -(hydroxyethyl), hydroxides, sodium salts (CAS no. 70983 -43 -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 reference value for the biodegradability of the test item was the chemical oxygen demand (COD).

The biodegradability of Imidazolium compounds, 2 -C4 -8 -alkyl-1 -(2 -carboxyethyl)-4,5 -dihydro-3 -(hydroxyethyl), hydroxides, sodium salts based on O₂consumption was calculated to be 20% after 28 days as compared to the chemical oxygen demand (COD).

The biodegradation reached 14% at the end of the 10-d window (i.e. within 10 days after attainment of 10% degradation).

Biodegradation of the test item started without any significant lag-phase.

The procedure control sodium benzoate reached 85% biodegradation after 14 days, thus confirming suitability of inoculum and test conditions.

The total elimination calculated based on dissolved organic carbon (DOC) measurements reached 24% for Imidazolium compounds, 2 -C4 -8 -alkyl-1 -(2 -carboxyethyl)-4,5 -dihydro-3 -(hydroxyethyl), hydroxides, sodium salts and 100% for sodium benzoate, respectively. This data is in line with the degradation calculated based on O₂ consumption.

Imidazolium compounds, 2-C4-8-alkyl-1-(2-carboxyethyl)-4,5 -dihydro-3 -(hydroxyethyl), hydroxides, sodium salts (CAS no. 70983 -43 -6) did not reach the pass level of 60% for ready biodegradability in the Manometric Respirometry Test neither within the 10 -d window nor after 28 days of incubation and, therefore, cannot be termed as readily biodegradable.

All validity criteria were fulfilled.

Description of key information

The biodegradability of Imidazolium compounds, 2-C4-8-alkyl-1-(2-carboxyethyl)-4,5-dihydro-3-(hydroxyethyl), hydroxides, sodium salts (CAS no. 70983-43-6) 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 (Arcadis Schweiz LTD, 2018). The reference value for the biodegradability of the test item was the chemical oxygen demand (COD).

The biodegradability of the substance based on O₂ consumption was calculated to be 20% after 28 days as compared to the chemical oxygen demand (COD). The total elimination calculated based on dissolved organic carbon (DOC) measurements reached 24%.

Imidazolium compounds, 2-C4-8-alkyl-1-(2-carboxyethyl)-4,5-dihydro-3-(hydroxyethyl), hydroxides, sodium salts (CAS no. 70983-43-6) did not reach the pass level of 60% for ready biodegradability in the Manometric Respirometry Test neither within the 10-d window nor after 28 days of incubation and, therefore, cannot be termed as readily biodegradable. This guideline study was rated with Klimisch 1.

Evaluation:

Based on the “Revised introduction to the OECD guidelines for testing of chemicals, Section 3” * , paragraph 36, the DOC elimination of 24%, together with the mineralization of 20% may indicate that the test item is “inherently, ultimately biodegradable”. Although this pass level of 20% (measured as BOD, DOC removal or COD) applies to inherent biodegradation tests, the fact that this pass level was reached in the present case in a ready biodegradation test (i.e. more stringent), can indeed be used to indicate an “inherent, ultimate biodegradability".

(*OECD, Revised introduction to the OECD guidelines for testing of chemicals, Section 3; Adopted 23 March 2006)

Therefore the test item is judged to be inherently ultimately biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

inherently biodegradable

Type of water:

freshwater