4,8-Dimethyl-2,5,7,10-tetraoxaundecane

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:

From 10 January 2022 to 17 February 2022

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)

Version / remarks:

July 17, 1992

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch number of test material: Lambiotte & Cie - 2101081010R

- Purity, including information on contaminants, isomers, etc.: purity 99.96% - water content 0.0019%


STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: At room temperature protected from light container flushed with nitrogen
- Solubility and stability of the test material in water: 26.0-27.9% at 20°C

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge (adaptation not specified)

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): 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.
- Freshly obtained sludge was kept under continuous aeration until further treatment. Before use, sludge was coarsely sieved (1 mm2 mesh) and homogenized using a blender on medium speed for approximately 1 minute. After treatment, concentration of suspended solids (SS) was determined to be 5.02 g/L in concentrated sludge as used for the test.
Magnetically stirred sludge was used as inoculum at an amount of 1.99 mL per liter of mineral medium, leading to a SS concentration of 10 mg/L.

Duration of test (contact time):

28 d

Initial conc.:

21.5 mg/L

Based on:

test mat.

Remarks:

corresponding to 12 mg TOC/L

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium:
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- RO water and made up to 1 liter, pH 7.4 ± 0.2
B) 22.50 g MgSO4.7H2O dissolved in Milli- RO water and made up to 1 liter.
C) 36.40 g CaCl2.2H2O dissolved in Milli- RO water and made up to 1 liter.
D) 0.25 g FeCl3.6H2O dissolved in Milli- RO water and made up to 1 liter.
Mineral medium: 1 L mineral medium contains: 10 mL of solution (A), 1 mL of solutions (B), (C), (D), and Milli- RO water.
- Synthetic air (CO2 < 1 ppm): A mixture of oxygen (ca. 20 %) and nitrogen (ca. 80 %) was passed through a vessel, containing 0.5 - 1 liter 0.0125 M Ba(OH)2 solution to trap CO2 which might be present in small amounts. Synthetic air was passed through the scrubbing solutions at a rate of approximately 1-2 bubbles per second (ca. 30-100 mL/min).
- Test temperature: 20-24°C
- pH: 7.2-7.6
- Suspended solids concentration: 10 mg/L
- Continuous darkness: yes


TEST SYSTEM
- Culturing apparatus: tests vessels - 2-liter amber glass bottles
- Number of culture flasks/concentration: Test suspension: containing test item and inoculum (2 vessels). Inoculum blank: containing only inoculum (2 vessels) Procedural control: containing
procedural control item, and inoculum (1 vessel). Toxicity control: containing test item, procedural control item, and inoculum (1 vessel).
- Preparation of vessels: At the start of the test (Day 0), test and procedural control item were added to vessels containing microbial organisms and mineral components. Volumes were made up to 2 L with Milli- RO water, resulting in the mineral medium described before. Three CO2-absorbers (vessels filled with 100 mL 0.0125 M Ba(OH)2) were connected in series to the exit aeration line of each test vessel.
- Method used to create aerobic conditions: Synthetic air (CO2 < 1 ppm)
- Measuring equipment: CO2 produced in each test vessel reacted with barium hydroxide in the gas scrubbing vessel and precipitated out as barium carbonate. The amount of CO2 produced was determined by titrating remaining Ba(OH)2 with 0.05 M standardized HCl (1:20 dilution from 1 M HCl (Titrisol® ampoule), Merck, Darmstadt, Germany).Titrations were made every second or third day during the first 10 days, and thereafter at least every fifth day until Day 29, for inoculum blank and test item. Titrations for procedural and toxicity control were made over a period of at least 14 days. Phenolphthalein (1 % solution in ethanol, Merck) was used as pH-indicator. Each time the CO2-absorber nearest to the test vessel was removed for titration; each of the remaining two absorbers were moved one position in the direction of the test vessel. A new CO2-absorber was placed at the far end of the series. On the penultimate day, pH of respective test suspensions was measured and 1 mL of concentrated HCl (37 %, Merck) was added to the inoculum blank and test suspension.
Vessels were aerated overnight to drive off CO2. Final titration was made on Day 15 (procedural and toxicity control) and on Day 29 (remaining vessels).

CONTROL AND BLANK SYSTEM
- Inoculum blank: contains only inoculum (2 vessels)
- Toxicity control: containing test item, procedural control item, and inoculum (1 vessel). Titrations for procedural and toxicity control were made over a period of at least 14 days.

Reference substance:

other: Sodium acetate

Key result

Parameter:

% degradation (CO2 evolution)

Value:

8

Sampling time:

29 d

Remarks on result:

other: first vessel; CO2 measured on Day 29 is actually part of CO2 production of Day 28, since microbial activity was ended on Day 28 by addition of concentrated HCl.

Key result

Parameter:

% degradation (CO2 evolution)

Value:

20

Sampling time:

8 d

Remarks on result:

other: second vessel

Details on results:

Relative biodegradation values calculated from measurements performed during the test period revealed 8 % and 20 % biodegradation of 4,8-Dimethyl-2,5,7,10-tetraoxaundecane for vessel A and B, respectively (based on ThCO2). Thus, the criterion for ready biodegradability (at least 60 % biodegradation within a 10-day window) was not met.
In the toxicity control, more than 25 % biodegradation occurred within 14 days (52 %, based on ThCO2). Therefore, the test item was considered not to inhibit microbial activity.
Functioning of the test system was checked by testing the procedural control item sodium acetate, which showed a normal biodegradation curve (75 % within 14 days)

Results with reference substance:

procedural control item sodium acetate showed a normal biodegradation curve of 75 % within 14 days

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

4,8-Dimethyl-2,5,7,10-tetraoxaundecane was not readily biodegradable under the conditions of the modified Sturm test.

Executive summary:

The objective of the study was to evaluate 4,8-Dimethyl-2,5,7,10-tetraoxaundecane for its ready biodegradability in an aerobic aqueous medium with microbial activity introduced by inoculation with activated sludge.

The study met the validity criteria prescribed by the Study Plan and was considered to be valid. Test conditions and results are presented in the table below:

Test Item:	4,8-Dimethyl-2,5,7,10-tetraoxaundecane
Appearance:	Clear colourless liquid
Purity:	99.96 %
Correction factor:	No correction factor required
Total Organic Carbon (TOC) content:	56 %
Theoretical CO2 production	2.06 mg CO2/mg
Preparation of test item solution(s):	1 g/L aqueous stock solution, dosed to test medium. Test media were continuously stirred throughout the test.
Experimental Set-up
Guideline(s)	OECD 301B
Test system:	Micro-organisms in activated sludge
Test concentration:	21.5 mg/L, corresponding to 12 mg TOC/L
Controls	Blank inoculum control, procedural control (procedural control item) and toxicity control (test item and procedural control item).
Number of replicates	2 replicates for the test item vessels and blank inoculum control, 1 replicate each for the procedural control and toxicity control.
Procedural control item	Sodium acetate
Test duration:	28 days for the test item treatment and inoculum blank, 14 days for the procedural control and toxicity control.
Measurements:	The amount of CO2 produced was determined by titration of Ba(OH)2 with HCl. Titrations were made every second or third day during the first 10 days, and thereafter at least every fifth day until Day 28. Titrations for procedural control and toxicity control were made over a period of at least 14 days.
Experimental conditions
pH and temperature	Within the ranges specified in OECD TG 301B
Light	Test media were incubated in the dark
Results
Biodegradation	8 % and 20 %
Toxicity	No inhibition of microbial activity.
Conclusion	4,8-Dimethyl-2,5,7,10-tetraoxaundecane was not readily biodegradable under the conditions of the modified Sturm test.

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Type of water:

other: activated sldge