Octanoic acid, monoester with glycerol

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:

27 Jul - 25 Aug 2022

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:

July 1992

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Landesamt für Umwelt Baden-Württemberg, Germany

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: municipal wastewater treatment plant AZV Breisgauer Bucht (predominantly domestic wastewater), sampling date of activated sludge: 26 July 2022,
- Preparation of inoculum for exposure: The activated sludge was washed twice with tap water by settling the sludge, decanting the supernatant and re-suspending the sludge. The sludge was aerated at ambient temperature until use.
- Concentration of sludge: 30 mg d.s./L
- Dry solids concentration: 4.27 g/L (drying at 105°C for 5 hours)
- Water filtered: no

Duration of test (contact time):

28 d

Initial conc.:

100 mg/L

Based on:

COD

Parameter followed for biodegradation estimation:

O2 consumption

Remarks:

BOD was determined and biodegradation in % chemical oxygen demand COD was calculated

Details on study design:

TEST CONDITIONS
- Composition of medium: according to the guideline
- Solubilising agent: none
- Test temperature: 21.3 – 21.5°C throughout the whole study and therefore within the required range of 22 ± 2°C
- pH: 7.5 (at the beginning and termination of test)
- pH adjusted: The pH of the mineral medium was 7.7 and was therefore adjusted to 7.5 with HCl. After preparation of test solutions, no pH adjustment was needed (pH: 7.5)
- Aeration of dilution water: yes, at least half an hour
- Susspended solids concentration: 30 mg d.s./L

TEST SYSTEM
- Culturing apparatus: OxiTop® (WTW / Xylem)
- Number of culture flasks/concentration: 3 replicates
- Method used to create aerobic conditions: inoculum was aerated until use (see details on inoculum and medium/test solutions were prepared under oxic conditions)
- Measuring equipment: Sensomat (AQUALYTIC®)
- Test performed in closed vessels: yes
- Test performed in open system: no
- Details of trap for CO2 if used: bottles were equiped with rubber quiver inserts for NaOH pellets, which absorb the carbon dioxide produced.

SAMPLING
- Sampling frequency and method: Every 112 minutes, the current pressure was measured and stored by each measuring head.
- Sterility check if applicable: not applicable
- Sample storage before analysis: no

CONTROL AND BLANK SYSTEM
- Inoculum blank: 3 replicates (only inoculum)
- Reference substance: 3 replicates (concentration corresponding to 99.8 mg COD/L)
- Toxicity control: 1 replicate (48.1 mg/L test item and 21 mg reference substance corresponding to a concentration of 200 mg/L COD)

Reference substance:

acetic acid, sodium salt

Parameter:

% degradation (O2 consumption)

Remarks:

COD (chemical oxygen demand)

Value:

85.3

Sampling time:

28 d

Details on results:

A degradation of >60% was reached on Day 6 and therefore within a 10-d window.
The degradation of the toxicity control after 14 days was >25%. Therefore, the test item had no inhibitory effect on the inoculum according to the criterion of the guideline.
The oxygen consumption of the blanks after 28 days was 20.6 mg/L.

Results with reference substance:

The reference compound sodium acetate reached the pass level of 60% COD within 5 days.

Table 1: Biodegradation in % of COD

	Test item			Tox control	Reference item
Test item* [mL/164 mL]	164			164
Reference item** [mL or mg/164 mL]				21	164	164	164
COD [mg/L]	100	100	100	199	99.8	99.8	99.8
Day	Degradation [%]
0	0	0	0	0	0	0	0
4	49.6	49.6	49.6	48.9	58.2	58.2	55.4
8	70.3	67.5	67.5	69.1	73.2	73.2	70.4
12	80.6	77.8	77.8	78.1	80.8	80.8	78.0
16	81.3	78.8	78.8	84.7	81.4	81.4	81.4
20	82.4	82.4	82.4	86.2	82.6	82.6	82.6
24	86.3	83.3	83.3	88.2	83.5	83.5	83.5
28	86.3	86.3	83.3	88.2	83.5	86.5	86.5

*stock solution of 128.0 mg/L

**reference vessels: stock solution of 128.0 mg/L, toxicity control: direct addition

Table 2: Validity criteria for OECD 301 F.

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%.	less than 20%	yes
Percentage degradation of the reference compound reached the pass level by day 14 (≥ 60%).	pass level of 60% COD reached within 5 days	yes
The toxicity control should degrade to at least 35% (based on DOC) or at least 25% (based on ThOD or ThCO2) within 14 d.	78.1 % on Day 12	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.	was within the range of 20 – 30 mg O2/L	yes

Validity criteria fulfilled:

yes

Remarks:

For details refer to field "any other information on results incl. tables"

Interpretation of results:

readily biodegradable

Description of key information

Readily biodegradable: 85.3% biodegradation after 28 d based on COD (OECD 301 F)

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater

Additional information

One GLP study according to the OECD guideline 301 F is available testing the ready biodegradability of the substance Octanoic acid, monoester with glycerol (CAS 26402-26-6). The study was conducted using as inoculum activated sludge from a wastewater treatment plant treating predominantly domestic wastewater. A toxicity control (with 48.1 mg test item/L and 21 mg/L reference item, corresponding to 199 mg/L COD) and a reference control were run in parallel. The substance was found to be readily biodegradable with a biodegradation of 85.3% based on chemical oxygen demand (COD) after 28 d. A degradation of > 60% was reached on Day 6 and therefore within a 10-d window. Based on the results from the toxicity control (>25% degradation already on Day 4) the test item had no inhibitory effect on the inoculum. The reference compound sodium acetate reached the pass level of 60% COD within 5 days. All validity criteria set out in the guideline were fulfilled and therefore the study is reliable.