Registration Dossier

Environmental fate & pathways

Biodegradation in water: screening tests

Currently viewing:

Administrative data

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:
31 May 2016 - 30 June 2016
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reference:
Composition 1
Qualifier:
according to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Version / remarks:
1992
Deviations:
no
Qualifier:
equivalent or similar to
Guideline:
EU Method C.4-E (Determination of the "Ready" Biodegradability - Closed Bottle Test)
Version / remarks:
1992
Deviations:
no
Qualifier:
equivalent or similar 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
Deviations:
no
GLP compliance:
yes (incl. certificate)
Test material information:
Composition 1
Oxygen conditions:
aerobic
Inoculum or test system:
natural water
Details on inoculum:
River water was sampled from the Rhine near Heveadorp, The Netherlands (26-05-2016). 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. River water without particles was used as inoculum. The particles were removed by sedimentation after 1 day while moderately aerating.
Duration of test (contact time):
28 d
Initial conc.:
2 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Remarks:
as percentage of ThOD
Details on study design:
TEST CONDITIONS
- Composition of medium: 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.
Nutrient solutions were prepared with deionized water from a water purification system, containing no more than 0.01 mg/L Cu (ISO/IEC 17025; non-GLP analysis)
- Test temperature: 22-24°C
- pH: 8.0 (throughout the test)
- pH adjusted: no
- Continuous darkness: yes

TEST SYSTEM
- Test bottles: 0.30 L BOD (biological oxygen demand) bottles with glass stoppers
- Preparation of test solution: 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 top with alumiminium foil and the content was mixed vigorously. Subsequently 0.2 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.
Each of the prepared solutions was dispensed into the respective group of BOD bottles so that all bottles were completely filled without air bubbles.
- Number of culture flasks/concentration: 10 bottles containing river water and silica gel with test substance; 6 bottles with river water and sodium acetate
- Method used to create aerobic conditions: aeration of medium prior to test start
- Measuring equipment: oxygen electrode (see above); pH was measured using a Eutech Cyberscan pH11 pH meter (Eutech Instruments, Nijkerk, The Netherlands); temperature was measured and recorded with a sensor connected to a data logger.
- Test performed in closed vessels due to significant volatility of test substance: yes
- Other:
* silica gel Davisil grade 636, pore size 60A, 35-60 mesh particle size (batch MKBL7108V)
* Sodium acetate was added to the bottles using a stock solution of 1.0 g/L.

SAMPLING
- Sampling frequency: at t=0 and t=7, 14, 21 and 28 days
- Sampling method: two replicate bottles of all series were withdrawn for analyses at specified times
- Sample storage before analysis: no

CONTROL AND BLANK SYSTEM
- Inoculum blank: 10 bottles containing only river water + 10 bottles containing river water and silica gel
- Abiotic sterile control: no
- Toxicity control: no, see also field 'Any other information on results'

STATISTICAL METHODS: not applied
Reference substance:
acetic acid, sodium salt
Remarks:
purity >99%
Test performance:
The validity of the test is demonstrated by an endogenous respiration of 1.1 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, sodium acetate, at day 14 was 89%. 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 (DOC removal)
Value:
77
Sampling time:
28 d
Details on results:
Over 60% biodegradation was achieved in a period of approximately 11 days immediately following the attainment of 10% biodegradation at day 2 (see Illustration).
Amyl cinnamic aldehyde diethyl acetal (multi-constituent) therefore fulfilled the 14-day time window (10-day time window for other OECD 301 tests) criterion for ready biodegradable compounds.
Amyl cinnamic aldehyde diethyl acetal (multi-constituent) should therefore be classified as readily biodegradable.
Results with reference substance:
At day 14, the reference substance was degraded for 89%.

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 because possible toxicity of amyl cinnamic aldehyde diethyl acetal (multi-constituent) to microorganisms degrading acetate is not relevant. 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.

Table I Dissolved oxygen concentrations (mg/L) in the closed bottles.

Time (days)

Oxygen concentration (mg/L)

OCS

Ot

OC

Oa

0

8.7

8.7

8.7

8.7

 

8.7

8.7

8.7

8.7

Mean

8.7

8.7

8.7

8.7

7

7.9

5.9

8.1

3.9

 

8.0

5.5

8.1

3.7

Mean

8.0

5.7

8.1

3.8

14

7.9

4.4

7.9

3.1

 

7.9

4.6

7.9

3.0

Mean

7.9

4.5

7.9

3.1

21

7.5

3.6

7.6

 

 

7.6

3.4

7.6

 

Mean

7.6

3.5

7.7

 

28

7.4

3.0

7.5

 

 

7.5

3.3

7.6

 

Mean

7.5

3.2

7.6

 

 

OcsRiver water with nutrients and silica gel.

OtRiver water with nutrients, test material (2.0 mg/L) and silica gel.

OcRiver water with nutrients.

OaRiver water with nutrients and sodium acetate (6.7 mg/L).

 

Table II Oxygen consumption (mg/L) and the percentages biodegradation of the test substance (BOD/ThOD) and sodium acetate (BOD/ThOD) in the Closed Bottle test.

 

Time (days)

Oxygen consumption (mg/L)

Biodegradation (%)

Test substance

Acetate

Test substance

Acetate

0

0.0

0.0

0

0

7

2.3

4.3

41

80

14

3.4

4.8

61

89

21

4.1

 

73

 

28

4.3

 

77

 

Validity criteria fulfilled:
yes
Remarks:
see field 'Test performance'
Interpretation of results:
readily biodegradable
Conclusions:
The substance is biodegraded by 77% at day 28 in the Closed Bottle test, meeting the 14-day window, and should therefore be classified as readily biodegradable.
Executive summary:

In order to assess the biodegradation of the substance, a screening test was performed according to OECD TG 301D (Closed Bottle test), adapted for poorly water soluble substances, and under GLP conditions. In this study river water was exposed to 2 mg/L of the substance for 28 days. The substance did not cause a reduction in the endogenous respiration. The reference item sodium acetate was biodegraded by 89% at day 14. Furthermore, all other validity criteria of the test were met. The substance was biodegraded by 77% at day 28 and meets the 14 -day window in the Closed Bottle test. Therefore the substance is classified as readily biodegradable.

Description of key information

In order to assess the biodegradation of the substance, a screening test was performed according to OECD TG 301D (Closed Bottle test), adapted for poorly water soluble substances, and under GLP conditions. In this study river water was exposed to 2 mg/L of the substance for 28 days. The substance did not cause a reduction in the endogenous respiration. The reference item sodium acetate was biodegraded by 89% at day 14. Furthermore, all other validity criteria of the test were met. The substance was biodegraded by 77% at day 28 and meets the 14 -day window in the Closed Bottle test. Therefore the substance is classified as readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information