Fatty acids, tall-oil, reaction products with acrylic acid

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:

20-6-2012 to 19-07-2012

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

12 september 2012

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
not relevant

Oxygen conditions:

aerobic

Inoculum or test system:

natural water

Details on inoculum:

River water was sampled from the river Rhine near Heveadorp, The Netherlands (14-06-2012). The nearest plant (Arnhem-Zuid) treating domestic waste water biologically was 3 km upstream. The river water was aerated for 7 days before use to reduce the endogenous respiration. River water without particles was used as inoculum. The particles were removed by sedimentation after 1 day while moderately aerating. The dry weight of suspended solids after removal of sediment particles is <2.0 mg/L.

Duration of test (contact time):

28 d

Initial conc.:

2 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

In the preliminary study (van Ginkel en Meussen, 2012) the appropriate conditions for the performance of the closed bottle test were investigated. The focus was on the method of introduction of the poorly water soluble test substance into the test solution and optimising the bioavailability. The results were used for optimalisation of the setup of the definitive study.

For the definitive test (van Ginkel, 2012) use was made of 10 bottles containing only inoculum, 10 bottles containing inoculum and test substance, and 6 bottles containing inoculum and sodium acetate. The zero time bottles were immediately analysed for dissolved oxygen. The remaining bottles were incubated in the dark. Dissolved oxygen concentration was analysed in two replicate bottles at days 7, 14, 21, and 28.


TEST CONDITIONS
- Composition of medium: The river water used in the Closed Bottle test was spiked per liter of water with 8.5 mg KH2PO4, 21.75 mg K2HPO4, 33.3 mg Na2HPO4•2H2O, 22.5 mg MgSO4•7H2O, 27.5 mg Ca¬Cl2, 0.25 mg FeCl3•6H2O. Ammoniumchloride was omitted from the medium to prevent nitrification.
- Test temperature: 22-24 °C
- pH: 8.2 at start of test, pH 8.1 and 8.0 at day 28.
- Suspended solids concentration: < 2.0 mg/L (dryweight)
- Continuous darkness: yes

SAMPLING
- Sampling frequency: day 0, 7, 14, 21 and 28


CONTROL AND BLANK SYSTEM
- Inoculum blank: 10 bottles

Reference substance:

acetic acid, sodium salt

Remarks:

initial test concentration 6.7 mg/L, ThOD is 0.78 mg/mg

Preliminary study:

The optimum conditions were the use of alkaline test solution and riverwater as inoculum. These have been selected for the definitive test.

Test performance:

The validity of the test is demonstrated by an endogenous respiration of 1.2 mg/L at day 28 (Table I). According to the criteria, it should be below 1.5
mg/L. Furthermore, the differences of the replicate values at day 28 were less than 20%. The biodegradation percentage of the reference compound, sodium acetate, at day 14 was 92. Finally, the validity of the test is shown by oxygen concentrations >0.5 mg/L in all bottles during the test period.

Parameter:

% degradation (O2 consumption)

Value:

63

Sampling time:

28 d

Details on results:

Inhibition of the endogenous respiration of the inoculum by the test substance at day 7 was not detected. Therefore, no inhibition of the biodegradation due to the initial test substance concentration is expected.

Results with reference substance:

The biodegradation of the reference compound, sodium actetate, at day 14 was 92%.

Dissolved oxygen concentrations (mg/L) in the closed bottles.

Time (days)	Oxygen concentration (mg/L)
	Oc	Ot	Oa
0	8.9	8.9	8.9
	8.9	8.9	8.9
Mean (M)	8.9	8.9	8.9
7	8.3	6.5	3.7
	8.2	6.2	3.5
Mean (M)	8.3	6.4	3.6
14	8.1	6.1	3.3
	7.9	5.7	3.1
Mean (M)	8.0	5.9	3.2
21	7.9	5.1
	7.9	4.9
Mean (M)	7.9	5.0
28	7.8	4.4
	7.6	4.5
Mean (M)	7.7	4.5

O_c       Mineral nutrient solution with only inoculum.

O_t       Mineral nutrient solution with test material (2.0 mg/L), and inoculum.

O_a       Mineral nutrient solution with sodium acetate (6.7 mg/L) and with inoculum.

 

 

 

Oxygen consumption (mg/L) and the percentages biodegradation of the test substance, 2-cyclohexene-1-octanoic acid, 5(or 6)-carboxy-4-hexyl- (BOD/ThOD) and sodium acetate (BOD/ThOD) in the Closed Bottle test.

Time (days)	Oxygen consumption (mg/L)		Biodegradation (%)
	Test substance	Acetate	Test substance	Acetate
0	0.0	0.0	0	0
7	1.9	4.7	37	90
14	2.1	4.8	41	92
21	2.9		57
28	3.2		63

 

 

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

Diacid 1550 was degraded by 63% after 28 days in the Closed Bottle Test. Diacid 1550 consists of alkyl chains and an aromatic moiety. The two phase degradation curve shows that the two moieties of Diacid 1550 are probably degradaded sequentially. The biodegradation of the seperate moieties is probably in line with the time window criterion. Therefore it is concluded that the substance is readily biodegradable.

Executive summary:

In order to assess the biotic degradation, a ready biodegradability test was performed which allows the biodegradability to be measured in an aerobic aqueous medium. The ready biodegradability was determined in the Closed Bottle test performed according to OECD (TG 301 D), EU (Method C.4.) and ISO (TG 10107), and in compliance with GLP. Diacid 1550 did not cause a reduction in the endogenous respiration. The test substance is therefore considered to be non-inhibitory to the inoculum. Diacid 1550 was biodegraded by 63% at day 28. Hence, this substance is classified as readily biodegradable. The test is valid as shown by an endogenous respiration of 1.2 mg/L. The oxygen concentration was always >0.5 mg/L in all bottles during the test period. Sodium acetate was degraded by 92% of its theoretical oxygen demand after 14 days.

Description of key information

In the Closed Bottle test according to OECD (TG 301 D) and under GLP, Diacid 1550 was biodegraded by 63% at day 28. Hence, this substance is classified as readily biodegradable (reliability 1).

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

The ready biodegradability was measured in three studies.

Two studies were performed according to the Modified OECD screening test (OECD TG 301E). This method is not appropriate for very lipophilic substances (Reliability 3). The disappearance of the test substance was below the pass level of 70% DOC removal in 28 days.

The key study was the Closed Bottle test according to OECD (TG 301D), EU (Method C.4.) and ISO (TG 10107). Diacid 1550 is non-inhibitory to the inoculum. Diacid 1550 was biodegraded by 63% (oxygen consumption) at day 28. Hence, this substance is classified as readily biodegradable.

Diacid 1550 consists of alkyl chains and an aromatic moiety. The two phase degradation curve shows that the two moieties of Diacid 1550 are probably degraded sequentially. The biodegradation of the separate moieties is probably in line with the time window criterion. Therefore it is concluded that the substance is readily biodegradable.

In view of the ready biodegradability, further studies on the biodegradability and the degradation products have not been carried out.