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:
29 June 2017 to 04 September 2017
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)
Qualifier:
according to
Guideline:
EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)
GLP compliance:
yes (incl. certificate)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: Totnes Sewage Treatment Works, Totnes, Devon, UK
- Storage conditions: aerated at room temperature at pH 7.0 ± 1.0.
- Storage length: 1 day
- Preparation of inoculum for exposure: Seven days prior to the exposure start the activated sludge was centrifuged, washed and re suspended in the mineral medium and the solids concentration determined. This sludge was then diluted in medium, added to test bottles and stirred until required for use. The seeded mineral medium was pre-conditioned for seven days to reduce the blank oxygen uptake readings in the test.
- Concentration of sludge: SS 2806 mg/L
Duration of test (contact time):
28 d
Initial conc.:
100 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Remarks:
calculated as BOD/COD
Details on study design:
TEST CONDITIONS
- Composition of medium: according to the guideline
- Additional substrate: none
- Solubilising agent (type and concentration if used): none
- Test temperature: 22 ± 1 °C
- pH: 7.4 ± 0.2 (actual 7.26)
- pH adjusted: no
- Sludge concentration: 30 mg/L
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: dark glass 500 mL bottle placed in incubator
- Number of culture flasks/concentration: 3
- Method used to create aerobic conditions: continuously stirred
- Measuring equipment: Oxitop respirometer
- Details of trap for CO2 and volatile organics if used: KOH

Examiniations
- Frequency: daily
- Method: measurement of decrease in pressure over 240 min period

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes (3 replicates)
- Abiotic sterile control: none
- Toxicity control: yes (3 replicates)

STATISTICAL METHODS: NA
Reference substance:
benzoic acid, sodium salt
Parameter:
other: % degradation BOD/COD
Value:
13
Sampling time:
3 d
Remarks on result:
other: start of degradation
Parameter:
other: % degradation BOD/COD
Value:
47
Sampling time:
13 d
Remarks on result:
other: end of 10 day window
Parameter:
other: % degradation BOD/COD
Value:
72
Sampling time:
28 d
Details on results:
The substance is UVCB, according to OECD and ECHA guidance documents, the 10-day window can be waived. Therefore, as > 60% biodegradation was achieved within 28 days the substance is readily biodegradable.
Initial pH 7.26, at 28 days 6.7 for substance
Initial pH 7.2, at 60 days 7.1-7.2 for inoculum blank (60 day due to perallel testing)

Day

Sodium benzoate

Biodegradation(%)

Test substance Biodegradation (%)

Toxicity control Biodegradation (%)

1

3

1

3

2

39

7

22

3

47

13

26

4

55

19

30

5

59

23

33

6

61

26

35

7

63

31

38

8

65

34

39

9

66

37

41

10

66

39

42

11

66

42

44

12

67

44

45

13

67

47

47

14

68

49

47

15

68

51

49

16

68

53

50

17

69

56

51

18

70

57

52

19

70

59

52

20

70

61

54

21

69

62

54

22

69

63

55

23

70

65

56

24

70

66

57

25

70

68

57

26

70

69

58

27

71

71

59

28

70

72

59

Biodegradation (%) =       Biological Oxygen Demand (g O2/g)× 100 / ThOD (1.67 g O2/g) and/or COD (1.94 g O2/g)

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable, but failing 10-day window
Conclusions:
The substance is a UVCB and although not meeting the 10-day window is considered readily biodegradable (see OECD and ECHA guidance)
Executive summary:

Subject

Determination of Ready Biodegradability

Guideline

OECD 301F: Manometric respirometry

Test concentration

Control and 100 mg/L

Length of test

28 days

Nominal

test temperature

22 ± 1°C

Mean degradation after 28 days

72%

Classification

Readily biodegradable

Reference substance

Sodium benzoate

Experimental values

Substance

Reference substance

 

Day

Mean percentage biodegradation

Day

Mean percentage biodegradation

 

5

23

5

59

 

10

39

10

66

 

15

51

15

68

 

20

61

20

70

 

28

72

28

70

Comments

The CODof the test substance was measured as1.94 g O2/g and the mean BOD value after 28 days was 1.40 g O2/g. The percentage degradation was calculated as (BOD/COD)´100

Conclusions

The substance attained a maximum mean level of biodegradation (based on the BOD:COD ratio) of 72% and the results showed good replication.

The substance exhibited the potential for rapid degradation and can be classified as inherently biodegradable.

As the substance is UVCB, according to OECD and ECHA guidance documents (references 3 and 4), the 10-day window can be waived. Therefore, as > 60% biodegradation was achieved within 28 days The substance is readily biodegradable.

Description of key information

In a study according to OECD 301F, the substance attained a maximum mean level of biodegradation (based on the BOD:COD ratio) of 72% over a 28 day period and the results showed good replication. As the substance is UVCB, according to OECD and ECHA guidance documents, the 10-day window can be waived. Therefore, as > 60% biodegradation was achieved within 28 days The substance is readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable
Type of water:
freshwater

Additional information