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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:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Principles of method if other than guideline:
Biodegradation study was conducted according to OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test) for evaluating the percentage biodegradability of test chemical.
GLP compliance:
no
Oxygen conditions:
not specified
Inoculum or test system:
other: Mixed inoculum
Details on inoculum:
Mixed Inoculum Preparation: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 107 to 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):
42 d
Initial conc.:
4 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
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 BOD bottles; with glass stoppers (125 ml), BOD incubator & oxygen electrode and meter.

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:
% degradation (O2 consumption)
Value:
10.55
Sampling time:
42 d
Remarks on result:
other: Other details not known
Details on results:
The oxygen consumed by the test systems was corrected for oxygen consumption occurring in the blank test systems.The BOD Values (mgO2/mg) and percent biodegradation results for each test system arereported in Tables 2 and 3, respectively. The BOD42 value of test chemical was observed to be 0.21 mgO2/mg. ThOD was determined by calculation as 1.99 mgO2/mg. % Degradation was calculated using the values of BOD and ThOD for test item and was determined to be 10.55%. The % degradation of procedure control (reference item) was also calculated using the values BOD & ThOD was determined to be 64.45%. Degradation of Sodium Benzoate exceeds 39.15% on 7 days & 52.4% on 14th day. The activity of the inoculum was thus verified and the test can be considered as valid.
Results with reference substance:
The % degradation of procedure control (reference item) was also calculated using the values BOD & ThOD was determined to be 64.45%. Degradation of Sodium Benzoate exceeds 39.15% on 7 days & 52.4% on 14th day. The activity of the inoculum was thus verified and the test can be considered as valid.

TABLE 1: D.O Values (mg/L)

No. of Days

Inoculum Blank

(Control)

Test Suspension

Procedure Control

(Reference Item)

0

6.54

5.41

6.12

7

6.32

5.3

3.3

14

6

5.3

2.1

21

5.8

4

0.8

28

5.6

3.7

0.2

35

5.2

3.3

0.2

42

4.8

2.8

0.1

TABLE 2: BOD Values (mg O2/mg)

 

No. of Days

Test Suspension

Procedure Control

(Reference Item)

0

0

0

7

-0.02

0.65

14

-0.1

0.87

21

0.16

1.14

28

0.19

1.24

35

0.19

1.14

42

0.21

1.07

 

TABLE 3: PERCENT BIODEGRDATION RESULTS

No. of Days

Test Suspension

Procedure Control

(Reference Item)

0

0%

0%

7

-1%

39.15%

14

-5.02%

52.4%

21

8.04%

68.67%

28

9.54%

74.69%

35

9.54%

68.67%

42

10.55%

64.45%

 

Table 4: BOD42, THOD AND % BIODEGRADATION VALUES

 

Method details

BOD42(mgO2/mg)

ThOD (mgO2/mg)

%Biodegradation

Test Item

0.21

1.99

10.55

Reference Item

1.07

1.66

64.45

Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
The test chemical undergoes 10.55 % biodegradation after 42 days in the test condition. Thus, the test chemical was considered to be not readily biodegradable in nature.
Executive summary:

42-days Closed Bottle test following the OECD guideline 301 D to determine the ready biodegradability of the test chemical. The study was performed at a temperature of 20°C. The test system included control, test item and reference item. Domestic waste water containing surface soil and soil samples was used as a test inoculum for this study. The concentration of test and reference item (Sodium Benzoate) chosen for both the study was 4 mg/L, while that of inoculum was 32 ml/l . OECD mineral medium was used for the study. 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 (reference item) was also calculated using the values BOD & ThOD was determined to be 64.45%. Degradation of Sodium Benzoate exceeds 39.15% on 7 days & 52.4% on 14th day. The activity of the inoculum was thus verified and the test can be considered as valid.The BOD42 value of test chemical was observed to be 0.21 mgO2/mg. ThOD was calculated as 1.99 mgO2/mg. Accordingly, the % degradation of the test chemical after 42 days of incubation at 20 ± 1°C according to Closed Bottle test was determined to be 10.55%. Based on the results, the test chemical, under the test conditions, was considered to be not readily biodegradable in nature.

Description of key information

42-days Closed Bottle test following the OECD guideline 301 D to determine the ready biodegradability of the test chemical (Experimental study report, 2017). The study was performed at a temperature of 20°C. The test system included control, test item and reference item. Domestic waste water containing surface soil and soil samples was used as a test inoculum for this study. The concentration of test and reference item (Sodium Benzoate) chosen for both the study was 4 mg/L, while that of inoculum was 32 ml/l . OECD mineral medium was used for the study. 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 (reference item) was also calculated using the values BOD & ThOD was determined to be 64.45%. Degradation of Sodium Benzoate exceeds 39.15% on 7 days & 52.4% on 14th day. The activity of the inoculum was thus verified and the test can be considered as valid. The BOD42 value of test chemical was observed to be 0.21 mgO2/mg. ThOD was calculated as 1.99 mgO2/mg. Accordingly, the % degradation of the test chemical after 42 days of incubation at 20 ± 1°C according to Closed Bottle test was determined to be 10.55%. Based on the results, the test chemical, under the test conditions, was considered to be not readily biodegradable in nature.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

42-days Closed Bottle test following the OECD guideline 301 D to determine the ready biodegradability of the test chemical (Experimental study report, 2017). The study was performed at a temperature of 20°C. The test system included control, test item and reference item. Domestic waste water containing surface soil and soil samples was used as a test inoculum for this study. The concentration of test and reference item (Sodium Benzoate) chosen for both the study was 4 mg/L, while that of inoculum was 32 ml/l . OECD mineral medium was used for the study. 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 (reference item) was also calculated using the values BOD & ThOD was determined to be 64.45%. Degradation of Sodium Benzoate exceeds 39.15% on 7 days & 52.4% on 14th day. The activity of the inoculum was thus verified and the test can be considered as valid. The BOD42 value of test chemical was observed to be 0.21 mgO2/mg. ThOD was calculated as 1.99 mgO2/mg. Accordingly, the % degradation of the test chemical after 42 days of incubation at 20 ± 1°C according to Closed Bottle test was determined to be 10.55%. Based on the results, the test chemical, under the test conditions, was considered to be not readily biodegradable in nature.