Fatty acids, coco, esters with 3,3'-oxybis[1,2-propanediol]

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:

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

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

Species/Origin: Aerobic activated sludge, microorganisms from a domestic waste water treatment plant was supplied by the sewage treatment plant Rossdorf, Germany.
Conditioning: The aerobic activated sludge used for this study was washed by centrifugation and the supernatant liquid phase was decanted. The solid material was re-suspended in tap water and centrifuged again. This procedure was done three times. An aliquot of the final sludge suspension was weighed, dried and the ratio of wet sludge to its dry weight was determined. Based on this ratio, calculated aliquots of washed sludge suspension, corresponding to 3.5 g dry material per litre were mixed with test water and aerated overnight. This suspension was used for the experiment.

Duration of test (contact time):

28 d

Initial conc.:

102.5 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

The purpose of this study was to determine the ready biodegradability of the test item. The test item was exposed to aerobic activated sludge from the aeration tank of a domestic waste water treatment plant for 28 days. The biodegradation was followed by the oxygen uptake of the microorganisms during exposure. As a reference item sodium benzoate was tested simultaneously under the same conditions as the test item, and functioned as a procedure control.
This type of study is recognized by the international test guidelines and should provide a rational basis to assess the ready biodegradation properties of the test item when incubated with aerobic activated sludge.

The test flasks were incubated at 22°C. The pressure decrease in the reaction vessels was measured over complete experimental phase of 28 days using the BSB/BOD-Sensor-System, Aqualytic Dortmund, Germany. The test flasks were closed gas-tight by a measuring head. Potassium hydroxide solution (45%) was used for trapping the produced carbon dioxide. The amount of O2 consumed by the activated sludge was calculated from the decrease of pressure in the reaction vessel.

Preparation of Test Flasks: The amounts of test item and reference item were directly weighed into the test flasks. No emulsifiers or solvents were used.
Incubation: The closed test flasks were incubated in a climatised chamber under continuous stirring. The consumption of oxygen was determined by measuring the change of pressure in the flasks. Evolved carbon dioxide was absorbed in an aqueous solution (45%) of potassium hydroxide.

Test Duration: 28 days

Measurement of Oxygen: The change of pressure in the test flasks was meas-ured by means of a manometric method (BSB/BOD-Sensor-System, Aqualytic Dortmund, Germany) each day.
Temperature: The temperature was recorded by means of the automated software AMR Wincontrol©.
pH-Value: pH-values were measured in procedure control, a separately prepared test flask with test item (to prevent loss of test item in the test flasks) and a separately prepared test flask without test item (control) at test start and in all flasks at the end of the test, except in the abiotic and toxicity control, using a pH-electrode WTW pH 340i.

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (O2 consumption)

Value:

76.5

St. dev.:

1.5

Sampling time:

28 d

Parameter:

COD

Value:

2.323 other: mg O2/mg test item

Results with reference substance:

Percentage Biodegradation: The reference item sodium benzoate was sufficiently degraded to 83% after 14 days and to 89% after 28 days of incubation.
Conclusion: The percentage biodegradation of the reference item confirms the suitability of the used aerobic activated sludge inoculum.

Percentage Biodegradation of Test Item, of Sodium Benzoate and of the Toxicity Control based on ThOD_NH4

Time	Percentage Biodegradation^1
(Days)	^Test item1		Sodium Benzoate^2	Toxicity control^1, 2
	Flask 1 [%]	Flask 2 [%]	Flask 5 [%]	Flask 7 [%]
1	13	12	32	11
2	17	17	46	16
3	22	22	54	21
4	29	26	68	43
5	32	29	70	45
6	34	31	76	48
7	37	32	74	50
8	39	36	77	54
9	42	38	80	56
10	43	39	78	57
11	47	43	81	59
12	48	44	80	61
13	50	49	83	62
14	52	51	83	64
15	57	57	86	64
16	59	59	86	64
17	63	61	86	64
18	65	63	86	64
19	68	66	87	64
20	70	68	87	64
21	69	69	86	64
22	72	71	86	64
23	72	71	86	64
24	74	73	86	64
25	74	73	89	64
26	76	73	89	64
27	76	75	89	64
28	78	75	89	64

            ¹ThOD_NH4of Test item: 2.323 mg O₂/mg test item
            ²ThOD_NH4of sodium benzoate: 1.666 mg O₂/mg reference item

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

The degradation rate of the test substance did not reach 60% within the 10-day window, but after 28 days, i.e. 76.5% biodegradation.
However, according to ECHA guidance document R.7b (section R.7.9.4.1 - Ready biodegradability; with reference to OECD), the 10-day window criterion does not apply to substances comprising a mixture of similar constituents, for which a sequential biodegradation may be assumed. This is the case for the submission substance.
Therefore, based on a biodegradation of 76.5% (based on BOD/ThOD_NH4; single replicates: 77% and 75%) within 28 days, the substance is considered to be readily biodegradable.

Executive summary:

The ready biodegradability of the test item in a manometric respirometry test was determined based on the procedures indicated by the following internationally accepted methods: EU method C.4 -D / OECD method 301 F.

Test Species: Aerobic activated sludge, microorganisms from a domestic waste water treatment plant was supplied by the sewage treatment plant Rossdorf, Germany.

Test Design: The test item was investigated for its ready biodegradability in a manometric respirometry test over a period of 28 days. The biodegradation was followed by the oxygen uptake of the microorganisms during exposure. As a reference item sodium benzoate was tested simultaneously under the same conditions as the test item, and functioned as a procedure control.

Endpoints: Degradation rate of test item calculated by the oxygen consumption of the aerobic activated sludge microorganisms after 28 days of incubation.

Biodegradation of the Test item: The criterion for ready biodegradability under the conditions of a manometric respirometry test is the 10-day window, describing the period between reaching at least 10% degradation and 60% degradation. This period should not exceed 10 days. The mean biodegradation of 10% of the test item was reached at day 1 (ThOD_NH4). At the end of the 10-day window at day 11, the degradation of the test item was 45% (ThOD_NH4) and therefore the 10 day window criterion formally was not passed.

However, according to ECHA guidance document R.7b (section R.7.9.4.1 - Ready biodegradability; with reference to OECD), the 10-day window criterion does not apply to substances comprising a mixture of similar constituents for which a sequential biodegradation may be assumed. This is the case for the submission substance. Therefore, based on a biodegradation of 76.5% (based on BOD/ThOD_NH4; single replicates: 77% and 75%) within 28 days, the substance is considered to be readily biodegradable.

Biodegradation of Sodium Benzoate: The reference item sodium benzoate was sufficiently degraded to 83% after 14 days and to 89% after 28 days of incubation, thus confirming the suitability of the aerobic activated sludge inoculum used.

Biodegradation of the Toxicity Control: In the toxicity control containing both, the test item and the reference item sodium benzoate, 64% biodegradation was noted within 14 days and after 28 days of incubation. According to the test guidelines, the test item can be assumed to be not inhibitory to the aerobic activated sludge microorganisms, because degradation was >25% within 14 days.

 

In conclusion, this study was classified acceptable and satisfied the guideline requirements for ready biodegradability studies.

Description of key information

The submission substance is readily biodegradable, i.e. 76.5% within 28 days (OECD 301F, 2017).

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

A reliable key study is available on the ready biodegradability of the submission substance according to OECD 301F and in compliance with GLP (RL1).

Aerobic activated sludge microorganisms from a domestic waste water treatment plant was supplied by the sewage treatment plant Rossdorf, Germany. The test item was investigated for its ready biodegradability in a manometric respirometry test over a period of 28 days. The biodegradation was followed by the oxygen uptake of the microorganisms during exposure. As a reference item sodium benzoate was tested simultaneously under the same conditions as the test item, and functioned as a procedure control. Degradation rate of test item was calculated by the oxygen consumption of the aerobic activated sludge microorganisms after 28 days of incubation.

 A mean biodegradation of 10% of the test item was reached by day 1 (ThOD_NH4). At the end of the 10-day window at day 11, the degradation of the test item was 45% (ThOD_NH4) and therefore, the 10 day window criterion formally was not passed. The mean biodegradation at test end after 28 days was 76.5% (ThOD_NH4). However, according to ECHA guidance document R.7b (section R.7.9.4.1 - Ready biodegradability; with reference to OECD), the 10-day window criterion does not apply to substances comprising a mixture of similar constituents for which a sequential biodegradation may be assumed. This is the case for the submission substance. Therefore, based on a mean biodegradation of 76.5% (based on BOD/ThOD_NH4; single replicates: 77% and 75%) within 28 days, the substance is considered to be readily biodegradable.

The study was classified acceptable and satisfied the guideline requirements for ready biodegradability studies.

[Type of water: freshwater]