Ethyl enantate

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:

11.03.1998 - 14.04.1998

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)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

- Source of inoculum/activated sludge: fresh activated sludge from a biological waste water treatment plant treating predominantly domestic sewage (City of Geneva, Aïre)
- Preparation of inoculum for exposure: sludge is washed 3 times in the mineral medium and kept aerobic until being used on the same day
- Concentration of sludge (nominal): 100 mg/mL

Duration of test (contact time):

ca. 34 d

Initial conc.:

ca. 100 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Test temperature: 22°C
- pH:7.4
- pH adjusted: no
- Suspended solids concentration: dry sludge suspended solids: 2.260g/L. To obtain a concentration of 30 mg/L in a 250 mL flask, 3.32 mL of sludge is needed.
- Test duration: 34 days

TEST SYSTEM
- Number of culture flasks/concentration: 4
- Measuring equipment: Respirometer SAPROMAT D 12, made by J.M. VOITH GmbH, D-7920 Heidenheim

CONTROL AND BLANK SYSTEM
- Toxicity control: yes

Reference substance:

benzoic acid, sodium salt

Parameter:

% degradation (O2 consumption)

Value:

74

Sampling time:

34 d

Key result

Parameter:

% degradation (O2 consumption)

Value:

73

Sampling time:

28 d

Parameter:

% degradation (O2 consumption)

Value:

63

Sampling time:

10 d

Results with reference substance:

Degradation of reference substance > 40% after 7 days and 65% after 14 days: the activity of the sludge is verified and the test is considered as valid.

Biological Oxygen Demand (BOD, mg O₂/L, adjusted to nominal concentrations):

	Day	1	5	11	14	28	34
BOD sludge	1st flask	8.0	18.0	22.0	22.0	28.0	28.0
	2nd flask	0.0	14.0	16.0	18.0	23.0	25.0
	mean	4.0	16.0	19.0	20.0	25.5	26.5
BOD test substance	1st flask	57.8	147.1	186.3	199.0	216.7	219.7
	2n flask	60.8	144.4	169.9	182.7	204.4	206.3
	1st fl. Corr	53.8	131.1	167.3	179.0	191.2	193.2
	2nd fl. Corr	56.8	128.4	150.9	162.7	178.9	179.8
% degr.	1st flask	21	52	66	71	76	76
	2nd flask	22	51	60	64	71	71
	mean	22	51	63	68	73	74

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

The test substance is considered as readily biodegradable.

Executive summary:

In the current study the ready biodegradability of the test substance was determined by the Manometric Respirometry according to OECD 301 F guideline without significant deviation.

The measured volume of inoculated mineral medium, containing a known concentration of test substance (100mg/L) is stirred in a closed flask at a constant temperature (22°C) for up to 28 days. The consumption of oxygen was determind by measuring the quantity of oxygen required to maintain constant the gas volume in the respirometer flask.

The amount of oxygen taken up by the microorganisms population during biodegradation of the test chemical is expressed as a percentage of ThOD (Theoretical Oxygen Demand).

The test substance undergoes 74% biodegradation after 34 days (73% after 28 days) in the test conditions. Biodegradation starts on day 1 and reaches 63% at the end of the 10-day window.

The test substance is considered to be readily biodegradable according to this test.

Description of key information

The test substance is considered to be readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

There are 2 studies available assessing the ready biodegradability of the test item.

In the key study the ready biodegradabilitywas determined by the Manometric Respirometry according to OECD 301 F guideline. The test substance (100 mg/L) was evaluated up to 28 days. The consumption of oxygen was determind by measuring the quantity of oxygen required to maintain constant the gas volume in the respirometer flask. The amount of oxygen taken up by the microorganisms population during biodegradation of the test chemical is expressed as a percentage of ThOD (Theoretical Oxygen Demand).

The test substance undergoes 74% biodegradation after 34 days (73% after 28 days) in the test conditions and reaches 63% at the end of the 10-day window, thus the test substance is considered to be readily biodegradable.

In the supporting study the biodegradability of the test substance was assessed in a closed bottle test (OECD 301D). The test substance was incubated with a mixed population of aquatic microorganisms for 28 days under aerobic conditions in the dark at 20 ± 1°C. Biodegradation of the test substance is determined based on the reduction of dissolved oxygen. The test concentration was 2.8 mg/L.

The pass level 60 % removal of ThOD has been reached within the test period. However, this pass value was not reached in a 14 -day window within the 28 day period. In parallel preparations with the reference substance sodium benzoate a degradation of 79 % was achieved within 14 days.

The test item has to be considered as not readily biodegradable.

Taken together, the test item should be considered as readily biodegradable.