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Environmental fate & pathways

Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
21 March - 19 April, 2007
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
Study has been performed according to OECD and/or EU guidelines and according to GLP principles.
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)
Deviations:
no
Qualifier:
according to
Guideline:
ISO DIS 9439 (Ultimate Aerobic Biodegradability - Method by Analysis of Released Carbon Dioxide)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source: municipal sewage treatment plant "Waterschap de Maaskant", 's-Hertogenbosch, The Netherlands, receiving predominnantly domestic sewage.
- Preparation of inoculum: before use, the sludge was allowed to settle (39 minutes) and the liquid was decanted for use at the amount of 10 ml/L of mineral medium.
- Pretreatment: none
- Concentration of sludge: 10 ml supernatant/L mineral medium
- Initial cell concentration: not determined
- water filtered: no
Duration of test (contact time):
29 d
Initial conc.:
33 other: mg/2L
Based on:
test mat.
Initial conc.:
12 mg/L
Based on:
TOC
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 21.5 and 23.0°C
- pH: Just before the start of the test: 7.5-7.6. On day 29: 7.6-7.9
- pH adjusted: no
- Aeration of dilution water: not before the test, the test is aerated continuously
- Suspended solids concentration: The concentration of suspended solids was 3.7 g/l in the concentrated sludge (information obtained from the municipal sewage treatment plant).
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: Test vessels: 2 litre all-glass brown coloured bottles
- Number of culture flasks/concentration: Test suspension: containing test substance and inoculum (2 bottles). Inoculum blank: containing only inoculum (2 bottles). Positive control: containing reference substance and inoculum (1 bottle). Toxicity control: containing test substance, reference substance and inoculum (1 bottle).
- Method used to create aerobic conditions: A mixture of oxygen (21%) and nitrogen (79%) was passed through a bottle, containing 0.5 - 1 litre 0.0125 M Ba(OH)2 solution to trap CO2 which might be present in small amounts. The synthetic air was sparged through the scrubbing solutions at a rate of approximately 1-2 bubbles per second (ca. 30-100 ml/min).
- Test performed in open system: yes
- Details of trap for CO2 and volatile organics if used: The CO2 produced in each test bottle reacted with the barium hydroxide in the gas scrubbing bottle and precipitated out as barium carbonate. The amount of CO2 produced was determined by titrating the remaining Ba(OH)2 with 0.05 M standardized HCl (1:20 dilution from 1 M HCl (Titrisol® ampul), Merck, Darmstadt, Germany). Titrations were made every second or third day during the first 10 days, and thereafter at least every fifth day until the 29th day. Each time the CO2-absorber nearest to the test bottle was removed for titration; each of the remaining two absorbers was moved one position in the direction of the test bottle. A new CO2-absorber was placed at the far end of the series. Phenolphthalein (1% solution in ethanol, Merck, Darmstadt, Germany) was used as pH-indicator. On the 28th day, the pH of the test suspensions was measured and 1 ml of concentrated HCl (37%, Merck, Darmstadt, Germany) was added to each bottle. The bottles were aerated overnight to drive off CO2 present in the test suspension. The final titration was made on day 29.

SAMPLING
- Sampling frequency: titrations were made on days: 2, 5, 7, 9, 14, 19, 23, 27 and 29.
- Sampling method: titration of whole volume of CO2-absorber

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Abiotic sterile control: no
- Toxicity control: yes
Reference substance:
acetic acid, sodium salt
Key result
Parameter:
% degradation (CO2 evolution)
Value:
11
Sampling time:
29 d
Details on results:
In the toxicity control more than 25% degradation occurred within 14 days (35%, based on ThCO2). Therefore, the test substance was assumed not to inhibit microbial activity.
Results with reference substance:
The positive control substance was degraded by at least 60% (74%) within 14 days.
Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
Ditetrahydrofurylpropane was not readily biodegradable under the conditions of the modified Sturm test presently performed.

Description of key information

A study was conducted according to OECD 301B. After 29 days, 11% of the substance had degraded.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

Ditetrahydrofurylpropane was not readily biodegradable under the conditions of the modified Sturm test performed.