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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
Justification for type of information:
Experimental result using OECD guidelines.
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Principles of method if other than guideline:
Biodegradation study was conducted according to OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test) for evaluating the percentage biodegradability of test chemical.
GLP compliance:
no
Oxygen conditions:
aerobic
Inoculum or test system:
other: mixture of domestic waste water, surface soil and soil samples
Details on inoculum:
Mixed Inoculum Preparation (In-House): Domestic waste water, surface soil and soil samples from polluted sites receiving predominantly domestic waste was collected and were mixed to get diluted suspension. The inoculum was kept aerobic until being used for experiment by supplying organic and inorganic sources required by micro flora to sustain at controlled laboratory conditions. This gave the bacterial count as 107to 108 CFU/ml. At the regular interval microbial plating was also performed on agar to confirm the vitality and CFU count of microorganism.
Duration of test (contact time):
28 d
Initial conc.:
100 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
other: BOD and ThOD
Details on study design:
TEST CONDITIONS
- Composition of medium: OECD mineral medium was used for the study
- Test temperature: 20°C
- Continuous darkness: Yes
- Other: The water used in this study is deionized water.

TEST SYSTEM
- Culturing apparatus: The apparatus used in this study is Respirometer BOD Sensor System (Code: F102B0133; non-automatic pressure measurement sensor system) and Respirometric incubator (FOC 120i)) by VELP Scientifica.

CONTROL AND BLANK SYSTEM
- Inoculum blank: it contains only test inoculum
- Procedure control: contains reference compound and inoculum
Reference substance:
other: Sodium Benzoate
Key result
Parameter:
other: BOD and ThOD
Value:
0.85
Sampling time:
28 d
Remarks on result:
other: Other details not known
Details on results:
The oxygen consumed by the test systems wascorrected for oxygen consumption occurring in the blank test systems.The DO depletion in the (control) at the end of test duration was determined to be 24.2 mgO2/l.The BOD28 value of test chemical was observed to be 0.026 mgO2/mg.ThoD was determined by calculation as 3.045 mgO2/mg. % Degradation was calculated using the values of BOD and ThOD for test substance. Accordingly, the % degradation of the test substance after 28 days of incubation at 20°C according to manometric respirometry test was determined to be 0.85 %. The % degradation of procedure control (reference substance) was also calculated using BOD & ThOD and was determined to be 79.36%. The DO depletion(mg O2/l) in inoculum blank on 28th day was 24.2 mg O2/l which fulfilled the validity criteria (i.e., The DO depletion of the inoculums blank is normally 20-30 mg O2/l and should not be greater than 60 mg/l in 28 days) for inoculum blank (control). Degradation of Sodium acetate exceeds 64% after 4 days. Thus the activity of the inoculums is verified and the test is considered as valid.
Results with reference substance:
The DO depletion(mg O2/l) in inoculum blank on 28th day was 24.2 mg O2/l which fulfilled the validity criteria (i.e., The DO depletion of the inoculums blank is normally 20-30 mg O2/l and should not be greater than 60 mg/l in 28 days) for inoculum blank (control). Degradation of Sodium acetate exceeds 64% after 4 days. Thus the activity of the inoculums is verified and the test is considered as valid.

TABLE 1

DO DEPLETION (Oxygen Consumed mg O2/l)

No. of Days

Control

Test Substance

Reference Substance

1

17.5

13.7

28.5

2

18

15.3

30

3

21.3

19.1

52.5

4

23.5

20.2

55

5

24.6

20.9

63

6

24.6

21.9

65

7

25.2

22.2

62.5

8

25.7

23.9

68.5

9

26

23.9

70

10

-

-

-

11

26.3

24.1

71

12

26.3

24.1

70.5

13

26.8

25.2

71.5

14

26.8

23.5

66

15

27.4

25.2

69

16

-

-

-

17

27.4

25.7

68

18

27.4

25.2

66

19

27.4

25.2

65.5

20

24.1

22.4

58.5

21

26.1

26.4

60

22

-

-

-

23

-

-

-

24

24

26.2

59.5

25

24.1

26.1

59.5

26

24.6

26.4

60.65

27

24.1

26.9

60.6

28

24.2

26.7

61.5

 

 

 

Table 2

BOD28, Calculated ThOD and % Biodegradation Values

Method details

BOD28(mgO2/mg)

ThOD (mgO2/mg)

% Biodegradation

Test Substance

0.026 mgO2/l

3.045 mg O2/mg

0.85 %

Reference Substance

0.373 mg O2/mg

0.470 mg O2/mg

79.36 %

Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
The test chemical undergoes 0.85% biodegradation after 28 days in the test condition. Biodegradation starts on day 21 and reaches 0.85% at the end of 28th days. Thus, the test chemical can be considered as not biodegradable.
Executive summary:

28-days Manometric respirometry test following the OECD guideline 301F to determine the ready biodegradability of the test chemical. The study was performed at a temperature of 20± 1°C. Mixture of domestic waste water, surface soil and soil samples was used as a test inoculum for the study. This inoculum was collected and were mixed to get diluted suspension. The inoculum was kept aerobic until being used for experiment by supplying organic and inorganic sources required by micro flora to sustain at controlled laboratory conditions.  This gave the bacterial count as 107to 108 CFU/ml. At the regular interval microbial plating was also performed on agar to confirm the vitality and CFU count of microorganism. OECD mineral medium was used for the study. The test system included control, test item and reference item. The concentration of test and reference item ( Sodium Benzoate) chosen for both the study was 100 mg/L, while that of inoculum was 10 ml/l. ThOD (Theoretical oxygen demand) of test and reference item was determined by calculation. % Degradation was calculated using the values of BOD and ThOD for test item and reference item. The % degradation of procedure control (Sodium Benzoate) was also calculated using BOD & ThOD and was determined to be 79.36%. The DO depletion(mg O2/l) in inoculum blank on 28th day was 24.2 mg O2/l which fulfilled the validity criteria (i.e., The DO depletion of the inoculums blank is normally 20-30 mg O2/l and should not be greater than 60 mg/l in 28 days) for inoculum blank (control). Degradation of Sodium acetate exceeds 64% after 4 days. Thus the activity of the inoculums is verified and the test is considered as valid.The BOD28 value of test chemical was observed to be 0.026 mgO2/mg. ThOD was calculated as 3.045 mgO2/mg. Accordingly, the % degradation of the test item after 28 days of incubation at 20 ± 1°C according to manometric respirometry test was determined to be 0.85%.Based on the results, the test item, under the test conditions, was considered to be not biodegradable at 20 ± 1°C over a period of 28 days.

Description of key information

28-days Manometric respirometry test following the OECD guideline 301F to determine the ready biodegradability of the test chemical (Experimental study report, 2015). The study was performed at a temperature of 20± 1°C. Mixture of domestic waste water, surface soil and soil samples was used as a test inoculum for the study. This inoculum was collected and were mixed to get diluted suspension. The inoculum was kept aerobic until being used for experiment by supplying organic and inorganic sources required by micro flora to sustain at controlled laboratory conditions.  This gave the bacterial count as 107to 108 CFU/ml. At the regular interval microbial plating was also performed on agar to confirm the vitality and CFU count of microorganism. OECD mineral medium was used for the study. The test system included control, test item and reference item. The concentration of test and reference item ( Sodium Benzoate) chosen for both the study was 100 mg/L, while that of inoculum was 10 ml/l. ThOD (Theoretical oxygen demand) of test and reference item was determined by calculation. % Degradation was calculated using the values of BOD and ThOD for test item and reference item. The % degradation of procedure control (Sodium Benzoate) was also calculated using BOD & ThOD and was determined to be 79.36%. The DO depletion(mg O2/l) in inoculum blank on 28th day was 24.2 mg O2/l which fulfilled the validity criteria (i.e., The DO depletion of the inoculums blank is normally 20-30 mg O2/l and should not be greater than 60 mg/l in 28 days) for inoculum blank (control). Degradation of Sodium acetate exceeds 64% after 4 days. Thus the activity of the inoculums is verified and the test is considered as valid.The BOD28 value of test chemical was observed to be 0.026 mgO2/mg. ThOD was calculated as 3.045 mgO2/mg. Accordingly, the % degradation of the test item after 28 days of incubation at 20 ± 1°C according to manometric respirometry test was determined to be 0.85%.Based on the results, the test item, under the test conditions, was considered to be not biodegradable at 20 ± 1°C over a period of 28 days.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

28-days Manometric respirometry test following the OECD guideline 301F to determine the ready biodegradability of the test chemical (Experimental study report, 2015). The study was performed at a temperature of 20± 1°C. Mixture of domestic waste water, surface soil and soil samples was used as a test inoculum for the study. This inoculum was collected and were mixed to get diluted suspension. The inoculum was kept aerobic until being used for experiment by supplying organic and inorganic sources required by micro flora to sustain at controlled laboratory conditions.  This gave the bacterial count as 107to 108 CFU/ml. At the regular interval microbial plating was also performed on agar to confirm the vitality and CFU count of microorganism. OECD mineral medium was used for the study. The test system included control, test item and reference item. The concentration of test and reference item ( Sodium Benzoate) chosen for both the study was 100 mg/L, while that of inoculum was 10 ml/l. ThOD (Theoretical oxygen demand) of test and reference item was determined by calculation. % Degradation was calculated using the values of BOD and ThOD for test item and reference item. The % degradation of procedure control (Sodium Benzoate) was also calculated using BOD & ThOD and was determined to be 79.36%. The DO depletion(mg O2/l) in inoculum blank on 28th day was 24.2 mg O2/l which fulfilled the validity criteria (i.e., The DO depletion of the inoculums blank is normally 20-30 mg O2/l and should not be greater than 60 mg/l in 28 days) for inoculum blank (control). Degradation of Sodium acetate exceeds 64% after 4 days. Thus the activity of the inoculums is verified and the test is considered as valid.The BOD28 value of test chemical was observed to be 0.026 mgO2/mg. ThOD was calculated as 3.045 mgO2/mg. Accordingly, the % degradation of the test item after 28 days of incubation at 20 ± 1°C according to manometric respirometry test was determined to be 0.85%.Based on the results, the test item, under the test conditions, was considered to be not biodegradable at 20 ± 1°C over a period of 28 days.