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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:
22 Mar 2017 to 19 Apr 2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reference:
Composition 0
Qualifier:
according to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Version / remarks:
1992
Qualifier:
according to
Guideline:
EU Method C.4-E (Determination of the "Ready" Biodegradability - Closed Bottle Test)
Version / remarks:
1992
Qualifier:
according to
Guideline:
ISO 10707 Water quality - Evaluation in an aqueous medium of the "ultimate" aerobic biodegradability of organic compounds - Method by analysis of biochemical oxygen demand (closed bottle test)
Version / remarks:
1994
GLP compliance:
yes (incl. certificate)
Remarks:
Akzo Nobel ,Environmental Chemistry, Zutphenseweg 10, 7418 AJ Deventer, The Netherlands
Test material information:
Composition 1
Oxygen conditions:
aerobic
Inoculum or test system:
natural water: freshwater
Details on inoculum:
River water was sampled from the Rhine near Heveadorp, The Netherlands (15-03-2017). The nearest plant (Arnhem-Zuid) treating domestic wastewater biologically was 3 km upstream. The river water was aerated for 7 days before use to reduce the endogenous respiration (van Ginkel and Stroo, 1992). River water without particles was used as inoculum. The particles were removed by sedimentation after 1 day while moderately aerating. The inoculum was not pre-exposed to the test substance.
Duration of test (contact time):
28 d
Initial conc.:
2 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- pH: The pH of the media was 8.0 at the start of the test. The pH of the media at day 28 was 8.0 (controls and test).
- Temperature: Temperatures were within the prescribed temperature range of 22 to 24°C.

TEST SYSTEM
- Test bottles: The test was performed in 0.30 L BOD (biological oxygen demand) bottles with glass stoppers.

NUTRIENTS AND STOCKS
The river water used in the Closed Bottle test was spiked per liter of water with 8.5 mg KH2PO4, 21.75 mg K2HPO4, 33.4 mg Na2HPO4·2H2O, 22.5 mg MgSO4·7H2O, 27.5 mg CaCl2, 0.25 mg FeCl3·6H2O. Ammonium chloride was not added to the river water to prevent nitrification. Accurate administering of the test substance was accomplished by preparing a solid stock of 3.0 mg of the test substance per g of silica gel in a 50-mL serum flask. Only part of the top layer of the silica gel was brought into contact with the test substance. The serum flask was closed with a screw and the content was mixed vigorously. Subsequently 0.20 g of silica gel with the test substance was added to the test bottles. The resulting concentration of test substance in the bottles was 2.0 mg/L. Next the bottles were filled with nutrient medium with inoculum and closed. Sodium acetate was added to the bottles using a stock solution of 1.0 g/L.

PROCEDURE
Use was made of 10 bottles containing only river water, 10 bottles containing river water and silica gel, 10 bottles containing river water and silica gel with test substance, 6 bottles with river water and sodium acetate. The concentrations of the test substance, and sodium acetate in the bottles were 2.0 and 6.7 mg/L, respectively. Each of the prepared solutions was dispensed into the respective group of BOD bottles so that all bottles were completely filled without air bubbles. The zero time bottles were immediately analyzed for dissolved oxygen using an oxygen electrode. The remaining bottles were closed and incubated in the dark. Two duplicate bottles of all series were withdrawn for analyses of the dissolved oxygen concentration at day 7, 14, 21, and 28.
Reference substance:
acetic acid, sodium salt
Test performance:
VALIDITY
The validity of the test is demonstrated by an endogenous respiration of 1.4 mg/L at day 28. Furthermore, the differences of the replicate values at day 28 were less than 20%. The biodegradation percentage of the reference compound was sufficient. Finally, the validity of the test is shown by oxygen concentrations >0.5 mg/L in all bottles during the test period.
Key result
Parameter:
% degradation (O2 consumption)
Value:
3
Sampling time:
28 d
Details on results:
For more detail, see 'Any other information on results incl. tables'.
Results with reference substance:
The biodegradation of the reference compound was 83% on day 14.

Table Oxygen consumption (mg/L) and the percentages biodegradation of the test substance (BOD/ThOD)  

Time (days)

Oxygen consumption (mg/L)

Biodegradation (%)

Test substance

Acetate

Test substance

Acetate

0

0.0

0.0

0

0

7

0.0

4.0

0

75

14

0.2

4.5

3

83

21

-0.1

 

0

 

28

0.2

 

3

 

THEORERTICAL OXYGEN DEMAND (ThOD)

The calculated theoretical oxygen demand (ThOD) of Orivone (mono-constituent) is 3.0 g O2/g test substance. This ThOD is calculated with the molecular formula of C11H20O of the isomers (99.8%). The ThOD of sodium acetate is 0.8 mg/mg.

TOXICITY

Inhibition of the degradation of a well-degradable compound, e.g. sodium acetate by the test substance in the Closed Bottle test was not determined. Inhibition of the endogenous respiration of the inoculum by the test substance at day 7 was not detected (Table I). Therefore, no inhibition of the biodegradation due to the "high" initial test substance concentration is expected.

Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
The substance showed 3% biodegradation within the 28-day test period of an OECD TG 301D study and is considered to be not readily biodegradable.
Executive summary:

The biodegradation potential of Orivone in water was determined in a screening study according to OECD TG 301D (Closed Bottle Test) and in compliance with GLP criteria. The test was performed according to slightly modified OECD, EU and ISO Test Guidelines: ammonium chloride was omitted from the medium to prevent oxygen consumption due to nitrification. In this study, 2 mg/L test substance was inoculated with river water for 28 days under aerobic conditions. At regular intervals throughout the incubation period the oxygen consumption was measured and compared to the ThOD as indication of biodegradation. The observed biodegradation percentages did not exceed 3%. Based on these findings the substance is classified as not readily biodegradable.

Description of key information

The biodegradation potential of Orivone in water was determined in a screening study according to OECD TG 301D (Closed Bottle Test) and in compliance with GLP criteria. The test was performed according to slightly modified OECD, EU and ISO Test Guidelines: ammonium chloride was omitted from the medium to prevent oxygen consumption due to nitrification. In this study, 2 mg/L test substance was inoculated with river water for 28 days under aerobic conditions. At regular intervals throughout the incubation period the oxygen consumption was measured and compared to the ThOD as indication of biodegradation. The observed biodegradation percentages did not exceed 3%.Based on these findings the substance is classified as not readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information