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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:
2 (reliable with restrictions)
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: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.

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
Key result
Parameter:
% degradation (O2 consumption)
Value:
51.52
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 1.25 mgO2/mg. ThOD was determined by calculation as 2.62 mgO2/mg. % degradation was calculated using the values of BOD and ThOD for test item and was determined to be 51.52% at 20 ± 1°C. The % degradation of procedure control (reference item) was also calculated using BOD & ThOD and was determined to be 75.3%. Degradation of Sodium Benzoate exceeds 46.38% on 7 days & 61.44% 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 BOD & ThOD and was determined to be 75.3%. Degradation of Sodium Benzoate exceeds 46.38% on 7 days & 61.44% 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

7.4

7.3

7.2

7

6.9

4

3.6

14

6.6

2

2.3

21

6.2

1.4

1.5

28

5.9

0.4

0.7

TABLE 2: BOD Values (mg O2/mg)

 

No. of Days

Test Suspension

Procedure Control

(Reference Item)

0

0

0

7

0.7

0.77

14

1.12

1.02

21

1.17

1.12

28

1.35

1.25

 

TABLE 3: PERCENT BIODEGRDATION RESULTS

No. of Days

Test Suspension

Procedure Control

(Reference Item)

0

0%

0%

7

26.71%

46.38%

14

42.74%

61.44%

21

44.65%

67.46%

28

51.52%

75.3%

 

Table 4: BOD28, THOD AND % BIODEGRADATION VALUES

 

Method details

BOD28(mgO2/mg)

ThOD (mgO2/mg)

%Biodegradation

Test Item

1.35

2.62

51.52

Reference Item

1.25

1.66

75.3

Validity criteria fulfilled:
yes
Interpretation of results:
inherently biodegradable
Conclusions:
The test chemical undergoes 51.52% biodegradation after 28 days in the test condition. Thus, the test item was considered to be inherently biodegradable in nature.
Executive summary:

28-days Closed Bottle test following the OECD guideline 301 D 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 a test inoculum for the 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 BOD & ThOD and was determined to be 75.3%.  Degradation of Sodium Benzoate exceeds 46.38% on 7 days & 61.44% on 14th day. The activity of the inoculum was thus verified and the test can be considered as valid. The BOD28 value of test chemical was observed to be 1.35 mgO2/mg. ThOD was calculated as 2.62 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 51.52%. Based on the results, the test item, under the test conditions, was considered to be inherently biodegradable in nature.

Description of key information

28-days Closed Bottle test following the OECD guideline 301 D to determine the ready biodegradability of the test item (Experimental study report., 2018). The study was performed at a temperature of 20°C. The test system included control, test item and reference item. Polyseed were used as a test inoculum for the 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 BOD & ThOD and was determined to be 75.3%.  Degradation of Sodium Benzoate exceeds 46.38% on 7 days & 61.44% on 14th day. The activity of the inoculum was thus verified and the test can be considered as valid. The BOD28 value of test chemical was observed to be 1.35 mgO2/mg. ThOD was calculated as 2.62 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 51.52%. Based on the results, the test item, under the test conditions, was considered to be inherently biodegradable in nature.

Key value for chemical safety assessment

Biodegradation in water:
inherently biodegradable

Additional information

28-days Closed Bottle test following the OECD guideline 301 D to determine the ready biodegradability of the test item (Experimental study report., 2018). The study was performed at a temperature of 20°C. The test system included control, test item and reference item. Polyseed were used as a test inoculum for the 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 BOD & ThOD and was determined to be 75.3%.  Degradation of Sodium Benzoate exceeds 46.38% on 7 days & 61.44% on 14th day. The activity of the inoculum was thus verified and the test can be considered as valid. The BOD28 value of test chemical was observed to be 1.35 mgO2/mg. ThOD was calculated as 2.62 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 51.52%. Based on the results, the test item, under the test conditions, was considered to be inherently biodegradable in nature.