3-(heptyloxy)propane-1,2-diol

Biodegradation in water: screening tests

Administrative data

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

01-Oct-2019 - 31-Oct-2019

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2019

Report date:

2020

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

adopted July 17, 1992

Deviations:

yes

Remarks:

A technical issue might be the reason for the lack of biodegradation in the toxicity control. Disregarding the results of the toxicity control did not impact the validity or outcome of the study.

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

3-octoxypropane-1,2-diol

Cas Number:

10438-94-5

Molecular formula:

C11H24O3

IUPAC Name:

3-octoxypropane-1,2-diol

Test material form:

liquid

Details on test material:

Storage Conditions: At room temperature protected from light container flushed with nitrogen.

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

Source: The source of test organisms was activated sludge freshly obtained from a municipal sewage treatment plant: 'Waterschap Aa en Maas', 's-Hertogenbosch, The Netherlands, receiving predominantly domestic sewage.
Treatment: Freshly obtained sludge was kept under continuous aeration until further treatment. Before use, sludge was coarsely sieved (1 mm). After treatment concentration of suspended solids (SS) was determined to be 3.1 g/L in concentrated sludge as used for the test. Magnetically stirred sludge was used as inoculum at an amount of 3 mL per litre of mineral medium, leading to a SS concentration of 9.3 mg/L

Duration of test (contact time):

28 d

Initial test substance concentration

Initial test substance concentration 1

Initial conc.:

18.5 mg/L

Based on:

test mat.

Initial test substance concentration 2

Initial conc.:

12 mg/L

Based on:

TOC

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: 1 litre mineral medium contains: 10 ml of solution (A), 1 ml of solutions (B) to (D) and Milli-RO water
Stock solutions of mineral components
A) 8.50 g KH2PO4; 21.75 g K2HPO4; 67.20 g Na2HPO4.12H2O; 0.50 g NH4Cl; dissolved in Milli-Q water and made up to 1 litre, pH 7.4 ± 0.2
B) 22.50 g MgSO4.7H2O dissolved in Milli-Q water and made up to 1 litre.
C) 36.40 g CaCl2.2H2O dissolved in Milli-Q water and made up to 1 litre.
D) 0.25 g FeCl3.6H2O dissolved in Milli-Q water and made up to 1 litre.
- Test temperature: between 22 and 23°C
- pH: At t=0 d: 7.6; At t=14d (procedure and toxicity control) 7.7 - 7.8; At t=28 d: 7.5 – 7.6 (blank control and test solution).
- pH adjusted: no
- Aeration: Constant aeration with a mixture of oxygen (ca. 20%) and nitrogen (ca. 80%)
- Suspended solids concentration: suspended solids (SS) was determined to be 3.1 g/L in concentrated sludge as used for the test. Magnetically stirred sludge was used as inoculum at an amount of 3 mL per litre of mineral medium, leading to a SS concentration of 9.3 mg/L.
- Illumination: Test media were excluded from light.
- Pre-incubation medium: The day before the start of the test (day -1) mineral components, Milli- RO water (ca. 80% of final volume) and inoculum were added to each bottle. This mixture was aerated with synthetic air overnight to purge the system of CO2.

TEST SYSTEM
- Culturing apparatus: 2 litre brown coloured glass bottles.
- Type and number of bottles:
Test suspension: containing test item and inoculum (2 bottles).
Inoculum blank: containing only inoculum (2 bottles)
Procedural control: containing procedural control item and inoculum (1 bottle).
Toxicity control: containing test item, procedural control item and inoculum (1 bottle).
- Test performed in open system: yes
- Details of trap for CO2 and volatile organics if used: Three CO2-absorbers (bottles filled with 100 mL 0.0125 M Ba(OH)2) were connected in series to the exit air line of each test bottle.

SAMPLING
- Sampling frequency: Titration were made on day 2, 5, 8, 12, 15, 19, 23 and 29
- Sampling method: Each time the CO2-absorber nearest to the test bottle was removed for titration; each of the remaining two absorbers were moved one position in the direction of the test bottle. A new CO2-absorber was placed at the far end of the series.

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Abiotic sterile control: no
- Toxicity control: yes

PREPARATION OF TEST SOLUTION
Since Saskine™ 80 was easily soluble in water, test media were prepared using a stock solution of 1 g/L in Milli- RO water (tap water purified by reverse osmosis; Millipore Corp., Bedford, Mass., USA). A weighed amount of 501.25 mg of Saskine™ 80 was dissolved in Milli- RO water and made up to 500 mL. After mixing (vortex) and stirring for 20 minutes the final stock solution was clear and colourless (pH 5.6). Aliquots of 37 mL of the stock solution were added to test item bottles A and B and the toxicity control. These test bottles contained medium with microbial organisms (final volume: 2 litres). Test solutions were continuously stirred during the test, to ensure optimal contact between test item and test organisms.

Reference substance

Reference substance:

acetic acid, sodium salt

Results and discussion

% Degradation

% Degradation 1

Key result

Parameter:

% degradation (CO2 evolution)

Value:

89

Sampling time:

28 d

% Degradation 2

Key result

Parameter:

% degradation (CO2 evolution)

Value:

95

Sampling time:

28 d

Details on results:

- ThCO2 of Saskine™ 80 was calculated to be 2.37 mg CO2/mg.
- Relative biodegradation values calculated from measurements performed during the test period revealed 89 % and 95 % biodegradation of Saskine™ 80, for vessel A and B, respectively (based on ThCO2). Furthermore, average biodegradation of Saskine™ 80 in vessel A and B reached ≥60 % within a 10-day window.
- In the toxicity control no biodegradation occurred within 14 days (0% trouhout the test). Since both test and reference item reached ≥60 % within a 10-day window it is clear that microbial activity was not inhibited. Since the result of the toxicity control did not affect the conclusion of this study, disregarding the results of the toxicity control did not impact the validity or outcome of the study.
- Functioning of the test system was checked by testing the procedural control item sodium acetate, which showed a normal biodegradation curve.

BOD5 / COD results

Results with reference substance:

Procedural control item was biodegraded by at least 60% (actual result: 82%) within 14 days.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

Saskine™ 80 was readily biodegradable under the conditions of the modified Sturm test.

Executive summary:

In a CO₂ Evolution Test performed according to OECD guideline 301B and GLP principles, the substance was evaluated for its ready biodegradability. The test was performed in an aerobic aqueous medium containing activated sludge over a period of 28 days. The test item was tested in duplicate at a target concentration of 18.5 mg/L, corresponding to 12 mg TOC/L. Additionally two innoculum blanks, one procedure control and one toxicity control were tested. Relative biodegradation values calculated from measurements performed during the test period revealed 89 % and 95 % biodegradation of Saskine™ 80, for vessel A and B, respectively (based on ThCO₂). Furthermore, average biodegradation of Saskine™ 80 in vessel A and B reached≥60 % within a 10-day window. In the toxicity control no biodegradation occurred within 14 days (0% throughout the test). Since both test and reference item reached≥60 % within a 10-day window it is clear that microbial activity was not inhibited. Since the result of the toxicity control did not affect the conclusion of this study, disregarding the results of the toxicity control did not impact the validity or outcome of the study.

All criteria for acceptability of the test were met, this study was considered to be valid.

In conclusion,Saskine™ 80 was readily biodegradable under the conditions of the modified Sturm test presently performed.