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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
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
GLP compliance:
yes (incl. certificate)
Specific details on test material used for the study:
Identification: 1,3-dichloro-2-propanol
Appearance: Colourless liquid
Batch: ZMG-197685
Purity/Composition: 99.2
Test item storage: At room temperature container flushed with nitrogen
Stable under storage conditions until: 09 December 2017 (expiry date)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, non-adapted
Details on inoculum:
Source: The source of test organisms was secondary effluent freshly obtained from a municipal sewage treatment plant: 'Waterschap Aa en Maas', 's-Hertogenbosch, The Netherlands, receiving predominantly domestic sewage.
Treatment: Secondary effluent was filtered through a coarse filter paper, the first 200 mL was discarded. The filtrate was kept aerated until inoculation.
Inoculation: 4 mL filtrate of secondary effluent per litre of final volume.
Reason for selection: The test has been accepted internationally (EC, OECD) for determining the 'ready' biodegradability of test items under aerobic conditions.
Duration of test (contact time):
28 d
Initial conc.:
ca. 2 mg/L
Based on:
test mat.
Initial conc.:
ca. 5 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
Test Concentration and Preparation of Test Solutions
1,3-dichloro-2-propanol was a colourless liquid with a purity of 99.2% (area). Nominal concentrations of 2 and 5 mg/L were tested. No correction was made for the purity/composition of the test item. All steps to prepare a test item stock solution were carried out in a glovebox under nitrogen.
Preparation of the test media started with a clear and colourless stock solution of 100 mg/L by adding 37 µL test item to 500 mL of mineral medium. Magnetic stirring (89 min) was applied to accelerate dissolution of the test item in mineral medium.
Microbial organisms and exact volumes of the stock solution, corresponding to the test concentrations, were added to the test medium.
Any residual volumes were discarded.

Test Procedure and Conditions
Test duration 28 days for the inoculum blank and test suspension
14 days for the procedure and toxicity control
Test bottles 250-300 mL BOD bottles with glass stoppers.
Milli-RO water Tap-water purified by reverse osmosis (Millipore Corp., Bedford, Mass., USA).
Stock solutions of A) 8.50 g KH2PO4
mineral components 21.75 g K2HPO4
67.20 g Na2HPO4.12H2O
0.50 g NH4Cl
dissolved in 1 litre Milli-RO water, pH 7.4 + 0.2
B) 22.50 g MgSO4.7H2O dissolved in 1 litre Milli-RO water.
C) 36.40 g CaCl2.2H2O dissolved in 1 litre Milli-RO water.
D) 0.25 g FeCl3.6H2O dissolved in 1 litre Milli-RO water.
Mineral medium 1 mL of solution (A) to (D) was mixed and made up to 1 litre with Milli-RO water.

The concentration of dissolved oxygen was measured for control purposes. The mineral medium was left at test temperature to obtain a saturated solution at the start of the test.

Test set up:
• Inoculum blank Containing only inoculum (no test item)
• Procedure control Containing reference item and inoculum
• Test suspension Containing test item and inoculum (applicable for both test concentrations)
• Toxicity control Containing test item at the lowest concentration, reference item and inoculum.
Number and groups of test Individual BOD bottles were prepared for each measuring
bottles point, except that the bottles measured at the start were also
measured on day 7.
Parallel groups were prepared to allow duplicate measurements
of oxygen consumption at the test intervals.
Illumination The test bottles were protected from light.

Determination of Frequency: In duplicate; immediately at the start of the
oxygen concentration: experiment (day 0), and at day 7, 14, 21 and 28.
Oxygen meter: WTW oxygen meter supplied with a WTW CellOx 325 oxygen electrode, electrolyte type ELY/G.
pH At the start of the test.
Temperature of medium Continuously in a vessel with Milli-RO water in the same room.


Reference substance:
acetic acid, sodium salt
Parameter:
% degradation (O2 consumption)
Value:
> -10 - < 5
Sampling time:
28 d
Details on results:
The relative biodegradation values calculated from the O2 measurements performed during the test period of 28 days revealed no biologically relevant biodegradation of
1,3-dichloro-2-propanol at both concentrations.
In the toxicity control more than 25% biodegradation occurred within 14 days (38% on day 14, based on ThOD). Thus, the toxicity control showed that 1,3-dichloro-2-propanol did not inhibit microbial activity.
Parameter:
ThOD
Value:
ca. 0.87 g O2/g test mat.
Results with reference substance:
72% biodegradation in 14 days
Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
1,3-dichloro-2-propanol was not readily biodegradable under the conditions of the closed bottle test presently performed.
Executive summary:

The objective of the study was to evaluate the organic test item 1,3-dichloro-2-propanol for its ready biodegradability in an aerobic, aqueous medium with microbial activity introduced by inoculation with secondary effluent during a test period of 28 days.

The study procedure described in this report was based onthe OECD guideline No. 301 D, 1992.

1,3-dichloro-2-propanol was a colourless liquid with a purity of 99.2% (area). The Theoretical oxygen demand (ThOD) of 1,3-dichloro-2-propanol was calculated to be 0.87 mg O2/mg. Nominal concentrations of 2 and 5 mg/L were tested. No correction was made for the purity/composition of the test item. All steps to prepare a test item stock solution were carried out in a glovebox under nitrogen.

The following test set up was applied:

·        Inoculum blank (only inoculum, no test item);

·        Procedure control (sodium acetate and inoculum);

·        Test item (1,3-dichloro-2-propanol at 2 mg/L and inoculum);

·        Test item (1,3-dichloro-2-propanol at 5 mg/L and inoculum);

·        Toxicity control (sodium acetate 2 mg/L, 1,3-dichloro-2-propanol at 2 mg/L and inoculum).

The test was performed in duplicate.

Measurements of the oxygen concentrations were performed at the start of the experiment (day 0) and on day 7, 14, 21 and 28.

The relative biodegradation values calculated from the O2measurements performed during the test period of 28 days revealed no biologically relevant biodegradation of 1,3-dichloro-2-propanol at both concentrations.

The toxicity control showed that 1,3-dichloro-2-propanol did not inhibit microbial activity. Since all criteria for acceptability of the test were met, this study was considered to be valid.

In conclusion, 1,3-dichloro-2-propanol is designated as not readily biodegradable.

Description of key information

The relative biodegradation values calculated from the O2measurements performed during the test period of 28 days revealed no biologically relevant biodegradation of 1,3-dichloro-2-propanol at 2mg/L and 5 mg/L.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed
Type of water:
freshwater

Additional information