Acetic acid, C11-14-isoalkyl esters, C13-rich

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:

2016-05-31 to 2016-06-30

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:

yes

Remarks:

a) NH4Cl was omitted from medium to prevent oxygen consumption due to nitrification (omission does not result in nitrogen limitation as shown by the biodegradation of acetic acid b) river water instead of an effluent/extract/mixture was used as inoculum

GLP compliance:

yes (incl. QA statement)

Remarks:

Date of inspection: 12-14/08/2014; Date of issue: 06/10/2014

Oxygen conditions:

aerobic

Inoculum or test system:

other: River water

Details on inoculum:

River water was sampled from the Rhine near Heveadorp, The Netherlands (26-05-2016). The nearest sewage treatment plant (Arnhem-Zuid) treating domestic wastewater biologically was 3 km upstream.

The river water was aerated for 7 days before use to reduce the endogenous respiration (van Ginkel and Stroo, 1992). River water without particles was used as inoculum. The particles were removed by sedimentation after 1 day while moderately aerating.

Duration of test (contact time):

28 d

Initial conc.:

2 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

DOC removal

Details on study design:

The Closed Bottle test was performed according to the study plan. The study plan was developed from ISO Test Guidelines (1994). Use was made of 10 bottles containing only river water, 10 bottles containing river water and silica gel, 10 bottles containing river water and silica gel with test substance, 6 bottles with river water and sodium acetate. The concentrations of the test substance, and sodium acetate in the bottles were 2.0 and 6.7 mg/L, respectively. Each of the prepared solutions was dispensed into the respective group of BOD bottles so that all bottles were completely filled without air bubbles. The zero time bottles were immediately analysed for dissolved oxygen using an oxygen electrode. The remaining bottles were closed and incubated in the dark. Two duplicate bottles of all series were withdrawn for analyses of the dissolved oxygen concentration at day 7, 14, 21, and 28.

Nutrients, and stocks
The river water used in the Closed Bottle test was spiked per liter of water with 8.5 mg KH2PO4, 21.75 mg K2HPO4, 33.4 mg Na2HPO4·2H2O, 22.5 mg MgSO4·7H2O, 27.5 mg CaCl2, 0.25 mg FeCl3·6H2O. Ammonium chloride was not added to the river water to prevent nitrification.

The test substance is poorly water soluble and volatile, and the test substance was therefore administered with the help of silica gel. Accurate administering of the test
substance was accomplished by preparing a solid stock of 3.0 mg of the test substance per g of silica gel in a 50-mL serum flask. Only part of the top layer of the silica gel was brought into contact with the test substance. The serum flask was closed with a screw top with aluminium foil and the content was mixed vigorously. Subsequently 0.2 g of silica gel with the test substance was added to the test bottles. The resulting concentration of test substance in the bottles was 2.0 mg/L. Next the bottles were filled with nutrient medium with inoculum and closed. Sodium acetate was added to the bottles using a stock solution of 1.0 g/L

Reference substance:

acetic acid, sodium salt

Preliminary study:

Preliminary study was not performed

Test performance:

The validity of the test is demonstrated by an endogenous respiration of 1.1 mg/L at day 28 (Table I). Furthermore, the differences of the replicate values at day 28 were less than 20%. The reference substance, sodium acetate, attained 89% biodegradation by day 14 (Table II). Finally, the validity of the test is shown by oxygen concentrations >0.5 mg/L in all bottles during the test period

Key result

Parameter:

% degradation (DOC removal)

Value:

75

Sampling time:

28 d

Details on results:

Acetic acid, C11-14-isoalkyl esters, C13-rich was biodegraded by 75% at day 28 in the Closed Bottle test (Table II). Over 60% biodegradation was achieved in a period of approximately 13 days immediately following the attainment of 10% biodegradation (Figure). Acetic acid, C11-14-isoalkyl esters, C13-rich should therefore be classified as readily biodegradable

Results with reference substance:

The reference substance, sodium acetate, attained 89% biodegradation by day 14

Theoretical oxygen demand (ThOD)

The theoretical oxygen demand (ThOD) of acetic acid, C11-14-isoalkyl esters, C13-rich was calculated with the C14 constituent and C15 constituent. The ThOD of the C14 constituent and C15 constituent are 2.80 and 2.84 mg/mg, respectively. The biodegradation percentages were calculated with the mean of ThOD of 2.8 mg/mg (rounded). The ThOD of sodium acetate is 0.8 mg/mg.

Toxicity

Inhibition of the test substance to microorganisms was not determined as part of the study.

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

Test conditions

The pH of the media was 8.0 at the start of the test. The pH of the media at day 28 was 8.0 (test and controls). Temperatures were within the prescribed temperature range of 22 to 24°C.

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

Time (days)	Oxygen concentration (mg/L)
	Ocs	Ot	Oc	Oa
0	8.7	8.7	8.7	8.7
	8.7	8.7	8.7	8.7
Mean (M)	8.7	8.7	8.7	8.7
7	7.9	7.1	8.1	3.9
	8.0	7.3	8.1	3.7
Mean (M)	8.0	7.2	8.1	3.8
14	7.9	5.6	7.9	3.1
	7.9	5.5	7.9	3.0
Mean (M)	7.9	5.6	7.9	3.1
21	7.5	3.4	7.6
	7.6	3.6	7.7
Mean (M)	7.6	3.5	7.7
28	7.4	3.1	7.5
	7.5	3.4	7.6
Mean (M)	7.5	3.3	7.6

 

O_cs River water with nutrients and silica gel.

O_t River water with nutrients, test material (2.0 mg/L) and silica gel.

O_c River water with nutrients.

O_a River water with nutrients and sodium acetate (6.7 mg/L).

 

Table II Oxygen consumption (mg/L) and the percentages biodegradation of the test substance (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	0.8	4.3	14	80
14	2.3	4.8	41	89
21	4.1		73
28	4.2		75

 

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

The substance attained 75% biodegradation in 28 days in a ready biodegradation study using a relevant test method (Closed Bottle Test) and in compliance with GLP. The result is considered to be reliable.

Executive summary:

In order to assess the biotic degradation of acetic acid, C11-14-isoalkyl esters, C13-rich, 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 slightly modified OECD, EU and ISO Test Guidelines, and in compliance with the OECD principles of Good Laboratory Practice.

Acetic acid, C11-14-isoalkyl esters, C13-rich did not cause a reduction in the endogenous respiration at day 7. The test substance is therefore considered to be non-inhibitory to the inoculum. Acetic acid, C11-14-isoalkyl esters, C13-rich was biodegraded by 75% at day 28 in the OECD 301 Closed Bottle test. Over 60% biodegradation was achieved in a period of approximately 13 days immediately following the attainment of 10% biodegradation. The substance fulfilled the 14-day time window criterion for ready biodegradable substances according to

OECD Test Guideline 301; Closed Bottle test. The substance should therefore be considered as readily biodegradable.

The test is valid as shown by an endogenous respiration of 1.1 mg/L and by the total mineralisation of the reference compound, sodium acetate. Sodium acetate was degraded by 89% of its theoretical oxygen demand after 14 days. Finally, the most important criterion was met by oxygen concentrations >0.5 mg/L in all bottles during the test period.

Description of key information

Biodegradation in water: readily biodegradable

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

The substance attained attained 75% biodegradation at day 28 in a closed-bottle study conducted in accordance with OECD Test Guideline 301D and in compliance with GLP. The result is considered to be reliable.