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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:
14 Oct - 11 Nov 2015
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
yes
Remarks:
; 20 °C instead of 22 °C
Qualifier:
according to
Guideline:
EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)
Deviations:
yes
Remarks:
; 20 °C instead of 22 °C
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: Collected from a municipal wastewater treatment plant in Usserød, Denmark.
- Laboratory culture: no
- Pretreatment: The activated sludge was stabilised under continuous aeration for a period of 2 d in order to reduce the content of easily degradable carbon.
- Concentration of sludge: 28.5 mg suspended solids (dry weight)/L
Duration of test (contact time):
28 d
Initial conc.:
22 mg/L
Based on:
test mat.
Initial conc.:
50.7 mg/L
Based on:
ThOD/L
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: according to guideline
- Test temperature: 19.8 ± 0.0 °C
- pH: 7.6 (test start); 7.5 - 7.6 (test end)
- pH adjusted: no
- Suspended solids concentration: 28.5 mg/L (dw)

TEST SYSTEM
- Culturing apparatus: WTW OxiTop® Control System (770 mL test volume)
- Number of culture flasks/concentration: 4
- Measuring equipment: WTW OxiTop® Control System
- Test performed in closed vessels due to significant volatility of test substance: no

SAMPLING
- Sampling frequency: continuously
- Sampling method: The OxiTop® Control system automatically determines the oxygen consumption in the test bottles.
- Sterility check if applicable: no
- Sample storage before analysis: not applicable

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes, 4 bottles
- Abiotic sterile control: no
- Toxicity control: yes, 4 bottles (containing approx. 22 mg/L test item and 20 mg/L of the reference substance)
- Other: Reference substance: yes, 4 bottles
Reference substance:
benzoic acid, sodium salt
Parameter:
% degradation (O2 consumption)
Value:
81
St. dev.:
3
Sampling time:
28 d
Details on results:
At the end of the 10-day window (from day 3 to day 13) a biodegradation of 65 ± 4% was measured.
Results with reference substance:
The reference substance was degraded to 78 ± 2% of ThOD after 14 d and 85 ± 5% of ThOD after 28 d.

The toxicity control attained 70% degradation after 14 d. Thus, the substance is not considered to be inhibitory to the inoculum.

Table 1: Degradation of the test substance during the test (average of four replicates)

Time [d]

Average degradation (BOD% of ThOD)

1

3.1

2

7.2

3

22.0

4

30.0

5

35.4

6

41.0

7

46.2

8

51.6

9

55.6

10

58.4

11

60.5

12

62.0

13

64.7

14

66.3

15

67.9

16

70.8

17

71.3

18

71.7

19

73.7

20

75.2

21

75.8

22

76.7

23

77.6

24

78.3

25

79.5

26

80.2

27

80.1

28

81.1

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable

Description of key information

One experimental study is available investigating the ready biodegradability of Glycerides, C16-18 and C18-unsatd. mono- and di-, citrates (CAS 91052-16-3). The study was performed according to OECD 301F (GLP) with a test concentration of 22 mg/L. Activated sludge from a municipal wastewater treatment plant was used as inoculum. During an incubation of 28 d the O2 consumption was measured continuously to calculate the biodegradation of the substance based on its ThOD. After 28 d a biodegradation rate of 81% (standard deviation 3%) was determined meeting the 10-day window. Thus, the substance is considered to be readily biodegradable according to the OECD criteria. Moreover, an additional toxicity control containing the test substance, the reference substance and inoculum indicated that Glycerides, C16-18 and C18-unsatd. mono- and di-, citrates is not inhibitory to the inoculum (70% degradation after 14 d).

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information