Oligo

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

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:

17 Jul 1992

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Kurume central sewage treatment center (Kurume-shi, Fukuoka, Japan); obtained on 04 Oct 2017
- Method of cultivation: After collection, the activated sludge was aerated at the test temperature until it was used für the test.

Duration of test (contact time):

28 d

Initial conc.:

100 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: according to guideline
- Test temperature: 22 °C
- pH: 7.3
- Suspended solids concentration: 30 mg/L
- Continuous darkness: yes
- Other: Each test solution was stirred with a stirrer.

TEST SYSTEM
- Culturing apparatus: Closed system oxygen consumption measuring apparatus (glass vessels)
- Number of culture flasks/concentration: 2
- Measuring equipment: automated measuring system
- Test performed in closed vessels due to significant volatility of test substance: yes
- Test performed in open system: no
- Details of trap for CO2 and volatile organics if used: Soda lime was used for absorption of evolved CO2.

SAMPLING
- Sampling frequency: O2 consumption was measured continuously.
- Sampling method: Automated measuring method.
- Other: During the incubation period, the appearance of the test solutions was observed once a day.

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes, two vessels
- Toxicity control: yes, one vessel
- Reference substance: yes, one vessel

Reference substance:

benzoic acid, sodium salt

Parameter:

% degradation (O2 consumption)

Value:

4

Sampling time:

28 d

Details on results:

The toxicity control resulted in a degradation of 35% after 14 d.
Undissolved material was oberserved in the test vessels during exposure.

Results with reference substance:

The reference substance was degraded to 89% after 14 d.

Table 1: % degradation of the test item, reference item and toxicity control

	7 d		14 d		21 d		28 d		Average
	BOD [mg]	% degradation	BOD [mg]	% degradation	BOD [mg]	% degradation	BOD [mg]	% degradation	% degradation
Test item	4.8	2	6.9	3	8.2	3	9.4	4	4
Test item	4.7	2	6.5	2	7.5	3	8.3	3
Toxicity control	45.7	33	50.3	35	53.3	37	55.2	38	-
Blank	3.5	-	4.9	-	5.7	-	6.4	-	-
Blank	3.3	-	4.6	-	5.4	-	6.0	-	-
Reference item	44.6	82	49.5	89	52.3	93	54.0	95	-

Table 2: Validity criteria for OECD 301.

Criterion from the guideline	Outcome	Validity criterion fulfilled
Difference of extremes of replicate values of the removal of the test chemical at the plateau, at the end of the test or at the end of the 10-d window, as appropriate, is less than 20%.	1%	yes
Percentage degradation of the reference compound has reached the pass levels by day 14.	89%	yes
The oxygen uptake of the inoculum blank is normally 20-30 mg O2/L and should not be greater than 60 mg/L in 28 days.	21 mg/L	yes
The toxicity control should degrade to at least 25% (based on ThOD or ThCO2) within 14 d.	35% after 14 d	yes

Validity criteria fulfilled:

yes

Remarks:

For further details please refer to “Any other information on results incl. tables”.

Interpretation of results:

under test conditions no biodegradation observed

Description of key information

Not readily biodegradable: 4% (O2 consumption, OECD 301F)

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Type of water:

freshwater

Additional information

One experimental study is available investigating the biodegradability of Fatty acids C16-18 (even numbered), oligoesters with sucrose. The study was performed according to OECD 301 F (GLP) with activated sludge from a domestic sewage treatment plant as inoculum. 100 mg of the test item was incubated with the activated sludge and the O2 consumption was followed continuously. In addition to the culture flasks with the test item a toxicity control containing both, test item and reference substance, as well as a positive control were run in parallel. After 28 d, 4% degradation of the test item was recorded indicating that Fatty acids C16-18 (even numbered), oligoesters with sucrose is not readily biodegradable according to the OECD criteria. The toxicity control resulted in a degradation of 35% after 14 d. Since the trigger of 25% degradation after 14 d is passed the test item is not considered to be inhibitory to the inoculum.