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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:
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 substance.
GLP compliance:
no
Oxygen conditions:
not specified
Inoculum or test system:
other: Mixed inoculum
Details on inoculum:
Mixed Inoculum Preparation:Polyseed were used for this study. 1 polyseed capsule was added in 500 ml D.I water and then stirred for 1 hour for proper mixing and functioning of inoculum. This gave the bacterial count as 10E7 to 10E8 CFU/ml. At the regular interval microbial plating was also performed on agar to confirm the vitality and CFU count of microorganism.

OR

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):
28 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
Parameter:
% degradation (O2 consumption)
Value:
76
Sampling time:
28 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 are reported in Tables 2 and 3, respectively. The BOD28 value of test chemical was observed to be 1.8 mgO2/mg. ThOD was determined by calculation as 1.25 mgO2/mg. % degradation was calculated using the values of BOD and ThOD for test item and was determined to be 76 % at 20 ± 1°C. The % degradation of procedure control (reference item) was also calculated using BOD & ThOD and was determined to be 79.51 %. Degradation of Sodium Benzoate exceeds 42.16 % on 7 days & 63.25 % on 14th day. The activity of the inoculum is 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 BOD & ThOD and was determined to be 79.51 %. Degradation of Sodium Benzoate exceeds 42.16 % on 7 days & 63.25 % on 14th day. The activity of the inoculum is 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

7

6.7

7

7

6.8

4.8

4

14

6.5

3.6

2.3

21

6.2

2.4

1.5

28

5.9

1.8

0.61

 

TABLE 2

BOD values (mgO2/mg)

No. of Days

 

Test Suspension

Procedure Control

(Reference Item)

0

0

0

7

0.42

0.7

14

0.65

1.05

21

0.87

1.17

28

0.92

1.32

 

TABLE 3

PERCENT BIODEGRDATION RESULTS

No. of Days

 

Test Suspension

Procedure Control

(Reference Item)

0

0%

0%

7

34%

42.16%

14

52%

63.25%

21

70%

70.48%

28

76%

79.51%

 

Table 4

BOD28, THOD AND % BIODEGRADATION VALUES

Method details

BOD28(mgO2/mg)

ThOD(mgO2/mg)

% Biodegradation

Test Item

0.95

1.25

76

Reference Item

1.32

1.66

79.51

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The test item undergoes 76 % biodegradation after 28 days in the test condition. Thus, the test item was considered to be readily biodegradable.
Executive summary:

28-days Closed Bottle test following the OECD guideline 301 D was performed to determine the ready biodegradability of the test item. The study was performed at a temperature of 20°C. The test system included control, test item and reference item. Polyseed were used as inovulum. The concentration of test and reference item (Sodium Benzoate) chosen for both the study was 4 mg/L, while that of inoculum was 32ml/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 BOD & ThOD and was determined to be 79.51 %. Degradation of Sodium Benzoate exceeds 42.16 % on 7 days &  63.25 on 14th day. The activity of the inoculum is thus verified and the test can be considered as valid. The BOD28 value of test chemical was observed to be 1.8 mgO2/mg. ThOD was calculated as 1.25 mgO2/mg. Accordingly, the % degradation of the test item after 28 days of incubation at 20 ± 1°C according to Closed Bottle test was determined to be 76 %. Based on the results, the test item, under the test conditions, was considered to be readily biodegradable in nature.

Description of key information

28-days Closed Bottle test following the OECD guideline 301 D was performed to determine the ready biodegradability of the test item. The study was performed at a temperature of 20°C. The test system included control, test item and reference item. Polyseed were used as inovulum. The concentration of test and reference item (Sodium Benzoate) chosen for both the study was 4 mg/L, while that of inoculum was 32ml/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 BOD & ThOD and was determined to be 79.51 %. Degradation of Sodium Benzoate exceeds 42.16 % on 7 days &  63.25 on 14th day. The activity of the inoculum is thus verified and the test can be considered as valid. The BOD28 value of test chemical was observed to be 1.8 mgO2/mg. ThOD was calculated as 1.25 mgO2/mg. Accordingly, the % degradation of the test item after 28 days of incubation at 20 ± 1°C according to Closed Bottle test was determined to be 76 %. Based on the results, the test item, under the test conditions, was considered to be readily biodegradable in nature.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

28-days Closed Bottle test following the OECD guideline 301 D was performed to determine the ready biodegradability of the test item. The study was performed at a temperature of 20°C. The test system included control, test item and reference item. Polyseed were used as inovulum. The concentration of test and reference item (Sodium Benzoate) chosen for both the study was 4 mg/L, while that of inoculum was 32ml/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 BOD & ThOD and was determined to be 79.51 %. Degradation of Sodium Benzoate exceeds 42.16 % on 7 days &  63.25 on 14th day. The activity of the inoculum is thus verified and the test can be considered as valid. The BOD28 value of test chemical was observed to be 1.8 mgO2/mg. ThOD was calculated as 1.25 mgO2/mg. Accordingly, the % degradation of the test item after 28 days of incubation at 20 ± 1°C according to Closed Bottle test was determined to be 76 %. Based on the results, the test item, under the test conditions, was considered to be readily biodegradable in nature.