Propyl oleate

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:

2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Deviations:

no

Qualifier:

equivalent or similar to guideline

Guideline:

EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Name: 9-Octadecenoic acid (9Z)-, propyl ester
Product Description: Propyl oleate
CAS No.: 111-59-1
Physical state: pale yellow to yellow liquid at 20 °C
Batch No.: 37584
Re-certification date of batch: 08 March 2018
Purity: > 99 % (fatty acid propyl esters, max water content 0.3 % (w/w))
Free Fatty Acid, % Oleic: 0.1
Color, Gardner: 3
Iodine Value, cg I2/g 75
Cloud Point, degrees C 0
Saponification Number, mg KOH/g 177
Moisture, % 0,07
Stability: stable under test conditions
Storage condition of test material: Room temperature, protected from light

Oxygen conditions:

aerobic

Inoculum or test system:

sewage, predominantly domestic, non-adapted

Details on inoculum:

Activated sludge from the municipal wastewater treatment plant Breisgauer Bucht was used as inoculum with a concentration corresponding to 30 mg dry solids per litre. The treatment plant clarifies predominantly domestic wastewater and has a capacity of 600.000 inhabitant equivalents. Sampling date of activated sludge was on 4 July 2017. The dry solid content of the activated sludge was 3.9 g/L. It was determined by weight measurements after drying at 105°C for 5 hours (mean of triplicate measurements). The activated sludge was washed twice with tap water by settling the sludge, decanting the supernatant and re-suspending the sludge.

Duration of test (contact time):

28 d

Initial conc.:

20 mg/L

Based on:

TOC

Parameter followed for biodegradation estimation:

CO2 evolution

Reference substance:

benzoic acid, sodium salt

Test performance:

Toxicity control: The degradation extent in the toxicity control was 73.5% within 14 days. According to the criterion of the guideline, the test substance had no inhibitory effect on the inoculum.

Reference item: The reference compound sodium benzoate reached the pass levels for ready biodegradability within 4 days (see table 1).

Blank: The mean CO2-evolution of the blank flasks was 31.6 mg/L on day 28 after acidification.

Test parameters:
- Before adding the test item, the IC in the reactor was determined, but only insignificant amounts of IC (0.39 mg/L) were found.
- The IC-concentration of the NaOH in the second CO2-absorber flasks in line, used as protective flasks, was below 7 ppm and was not considered in the data processing, because CO2 absorption from room air was its source.
- The temperature was 19.2 – 22.3°C throughout the whole study and therefore temporarily below the required range of 22 ± 2°C. Since the CO2 evolution in the blank flasks was in the tolerated range and the biodegradation of the reference compound reached 60% within 4 days, it is concluded that the deviation had no effect on the validity of the test.
- The aeration rate was in the tolerated range of 1.6 – 5.5 bubbles/second (counted bubbles: 2.8 – 5.4 bubbles/second).

Criteria of validity
- The IC content in the test vessel was less than 5% of the TOC introduced with the test item.
- The CO2 evolution in the inoculum blank at the end of the test was below 40 mg/L.
- The difference of extremes of replicate values of the test item at the end of the test was less than 20%.
- The biodegradation of the reference compound reached the pass level of 60% ThCO2 by day 4.
- The degradation extent in the toxicity control was above 25% in 14 days based on ThCO2.

The test is valid according to OECD Test Guideline 301 B (July 1992).

Key result

Parameter:

% degradation (CO2 evolution)

Value:

88

Sampling time:

28 d

Remarks on result:

other: mean of three replicate values

Parameter:

% degradation (CO2 evolution)

Value:

72.9

Sampling time:

7 d

Remarks on result:

other: mean of three replicate values

Details on results:

The degradation of the test item at the end of the test was 88.0% (28 d after acidification, mean of three replicates). The test item reached the criteria for ready biodegradability (60% of ThCO2 within a 10-d window).
The degradation of the toxicity control after 14 days was 73.5%. The test item had no inhibitory effect on the inoculum according to the criterion of the guideline.

Results with reference substance:

The biodegradation of the reference compound reached the pass level of 60% ThCO2 by day 4.

Results

Table 1: Ultimate biodegradation after x days [% of ThCO2]

reactor	day	0	4	7	11	14	21	28	29
19	Test flasks	0	19.6	65.5	77.9	76.0	80.1	81.7	80.3
20		0	58.7	75.9	88.4	84.8	90.2	94.2	91.1
21		0	55.6	77.0	89.6	88.3	90.0	95.9	92.5
4	Reference flasks	0	75.4	86.3	88.4	89.5	90.6	93.1	96.8
5		0	77.7	82.7	84.7	87.1	86.0	90.4	94.6
6		0	72.8	80 .7	86.7	87.8	87.6	88.9	91.8
22	Toxicity control - test item & reference item	0	41.1	58.9	72.6	73.5	78.4	83.5	81.1

Table 2: Mean CO2 evolution of blanks after x days

Day	0	4	7	11	14	21	28	29
CO2 -evolution [mg/l]	0	9.6	14.2	18.5	21.7	25.6	30.5	31.6

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

In a Klimisch 1 OECD 301 B study the degradation of the test item at the end of the test was 88.9 % (28 d after acidification, mean of three replicates). The test item reached the criteria for ready biodegradability (60% of ThCO2 within a 10-d window).

Executive summary:

In a Klimisch 1 OECD 301 B study the degradation of the test item at the end of the test was 88.9 % (28 d after acidification, mean of three replicates). The test item reached the criteria for ready biodegradability (60% of ThCO2 within a 10-d window). The degradation of the toxicity control after 14 days was 73.5%. The test item had no inhibitory effect on the inoculum according to the criterion of the guideline. The test is valid according to OECD 301 B (July 1992).

Description of key information

In a Klimisch 1 OECD 301 B study the degradation of the test item at the end of the test was 88.9 % (28 d after acidification, mean of three replicates). The test item reached the criteria for ready biodegradability (60% of ThCO2 within a 10-d window).

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable