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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 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 mixed inoculum. One capsule of Polyseed were added in 500 ml of DI water to make up the solution. Afterwards 1 hour of stirring were given for proper mixing of mixed 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):
35 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:
33.07
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 arereported in Tables 2 and 3, respectively. The BOD28 value of test chemical was observed to be 0.87mgO2/mg. ThOD was determined by calculation as 2.63 mgO2/mg. % Degradation was calculated using the values of BOD and ThOD for test item and was found to be 33.07% at 20 ± 1°C. The % degradation of procedure control (reference item) was also calculated using the values of BOD & ThOD and was found to be 73.49% at 20 ± 1°C. Degradation of Sodium Benzoate exceeds 31.32% on 7 days & 49.39 % on 14th day. The activity of the inoculum is thus verified and the test can be considered as valid.
Results with reference substance:
Degradation of Sodium Benzoate exceeds 31.32% on 7 days & 49.39% on 14th day. The % degradation of procedure control (reference item) was also calculated using the values of BOD & ThOD and was found to be 73.49 % at 20 ± 1°C.

TABLE 1

D.O Values(mg/L)

No. of Days

Inoculum Blank

(Control)

 

Test Suspension

Procedure Control

(Reference Item)

 

0

6.6

6.6

6.6

7

6

4.4

3.9

14

5.8

4

2.5

21

5.7

3.7

1.2

28

5.6

3.2

0.7

35

5.4

1.9

0.5

 

TABLE 2

BOD values (mgO2/mg)

No. of Days

Test Suspension

Procedure Control

(Reference Item)

 

0

0

0

7

0.37

0.52

14

0.45

0.82

21

0.5

1.12

28

0.6

1.22

35

0.87

1.22

 

TABLE 3

PERCENT BIODEGRDATION RESULTS

No. of Days

Test Suspension

Procedure Control

(Reference Item)

 

0

0%

0%

7

14.06%

31.32%

14

17.11%

49.39%

21

19.01%

67.46%

28

22.81%

73.49%

35

33.07%

73.49%

 

Table 4

BOD35, THOD AND % BIODEGRADATION VALUES

Method details

BOD35 (mgO2/mg)

ThOD (mgO2/mg)

% Biodegradation

 

TestItem

0.87

2.63

33.07

ReferenceItem

1.22

1.66

73.49

Validity criteria fulfilled:
yes
Interpretation of results:
inherently biodegradable, fulfilling specific criteria
Conclusions:
The test chemical undergoes 33.07 % biodegradation after 35 days in the test condition. Thus, the test chemical was considered to be primary inherently biodegradable in nature.
Executive summary:

35-days Closed Bottle test following the OECD guideline 301 D was performed to determine the ready biodegradability of the test chemical. 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 4 mg/L, while that of inoculum was 32 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 BOD35 value of test chemical was observed to be 0.87 mgO2/mg. ThOD was calculated as 2.63 mgO2/mg. Accordingly, the % degradation of the test item after 35 days of incubation at 20 ± 1°C according to Closed Bottle test was determined to be 33.07 %. Based on the results, the test chemical, under the test conditions was considered to be primary inherently biodegradable at 20 ± 1°C over a period of 35 days.

Description of key information

35-days Closed Bottle test following the OECD guideline 301 D was performed to determine the ready biodegradability of the test chemical. 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 4 mg/L, while that of inoculum was 32 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 BOD35 value of test chemical was observed to be 0.87 mgO2/mg. ThOD was calculated as 2.63 mgO2/mg. Accordingly, the % degradation of the test item after 35 days of incubation at 20 ± 1°C according to Closed Bottle test was determined to be 33.07 %. Based on the results, the test chemical, under the test conditions was considered to be primary inherently biodegradable at 20 ± 1°C over a period of 35 days.

Key value for chemical safety assessment

Biodegradation in water:
inherently biodegradable

Additional information

35-days Closed Bottle test following the OECD guideline 301 D was performed to determine the ready biodegradability of the test chemical. 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 4 mg/L, while that of inoculum was 32 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 BOD 35 value of test chemical was observed to be 0.87 mgO2/mg. ThOD was calculated as 2.63 mgO2/mg. Accordingly, the % degradation of the test item after 35 days of incubation at 20 ± 1°C according to Closed Bottle test was determined to be 33.07 %. Based on the results, the test chemical, under the test conditions was considered to be primary inherently biodegradable at 20 ± 1°C over a period of 35 days.