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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 standard OECD guidelines.
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
GLP compliance:
no
Oxygen conditions:
aerobic
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):
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:
benzoic acid, sodium salt
Key result
Parameter:
% degradation (O2 consumption)
Value:
39.21
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 are reported in Tables 2 and 3, respectively. The BOD42 value of test chemical was observed to be 0.4 mgO2/mg. ThOD was determined by calculation as 1.02 mgO2/mg. % degradation was calculated using the values of BOD and ThOD for test chemical and was determined to be 39.21% at 20 ± 1°C. The % degradation of procedure control (reference chemical) was also calculated using BOD & ThOD and was determined to be 66.26%. Degradation of Sodium Benzoate exceeds 70.48% on 7 days & 73.49% 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 chemical) was also calculated using BOD & ThOD and was determined to be 66.26%. Degradation of Sodium Benzoate exceeds 70.48% on 7 days & 73.49% 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

6.8

6.7

6.7

7

6.5

5.5

1.7

14

6.3

4.9

1.2

21

6

4.6

0.8

28

5.6

3.9

0.7

35

5.3

3.7

0.6

42

5.1

3.4

0.6

TABLE 2: BOD Values (mg O2/mg)

 

No. of Days

Test Suspension

Procedure Control

(Reference Item)

0

0

0

7

0.22

1.17

14

0.32

1.22

21

0.32

1.27

28

0.4

1.2

35

0.37

1.15

42

0.4

1.1

 

TABLE 3: PERCENT BIODEGRDATION RESULTS

No. of Days

Test Suspension

Procedure Control

(Reference Item)

0

0%

0%

7

21.56%

70.48%

14

31.37%

73.49%

21

31.37%

76.5%

28

39.21%

72.28%

35

36.27%

69.27%

42

39.21%

66.26%

 

Table 4: BOD42, THOD AND % BIODEGRADATION VALUES

 

Method details

BOD42(mgO2/mg)

ThOD (mgO2/mg)

%Biodegradation

Test Item

0.40

1.02

39.21

Reference Item

1.10

1.66

66.26

Validity criteria fulfilled:
yes
Interpretation of results:
inherently biodegradable
Conclusions:
The test chemical undergoes 39.21% biodegradation after 28 days in the test condition. Thus, the test chemical was considered to be inherently biodegradable.
Executive summary:

Biodegradation study was conducted for 42-days in accordance with 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 chemical and reference substance. Polyseed were used as a test inoculum for the study. The concentration of test and reference chemical (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 chemical) was also calculated using BOD & ThOD and was determined to be 66.26%. Degradation of Sodium Benzoate exceeds 70.48% on 7 days & 73.49% on 14th day. The activity of the inoculum is thus verified and the test can be considered as valid.The BOD42 value of test chemical was observed to be 0.4 mgO2/mg. ThOD was calculated as 1.02 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 39.21%. Based on the results, the test chemical, under the test conditions, was considered to be inherently biodegradable in nature.

Description of key information

Biodegradation study was conducted for 42-days in accordance with the OECD guideline 301 D to determine the ready biodegradability of the test chemical (Experimental study report, 2019). The study was performed at a temperature of 20°C. The test system included control, test chemical and reference substance. Polyseed were used as a test inoculum for the study. The concentration of test and reference chemical (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 chemical) was also calculated using BOD & ThOD and was determined to be 66.26%. Degradation of Sodium Benzoate exceeds 70.48% on 7 days & 73.49% on 14th day. The activity of the inoculum is thus verified and the test can be considered as valid. The BOD42 value of test chemical was observed to be 0.4 mgO2/mg. ThOD was calculated as 1.02 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 39.21%. Based on the results, the test chemical, 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

Biodegradation study was conducted for 42-days in accordance with the OECD guideline 301 D to determine the ready biodegradability of the test chemical (Experimental study report, 2019). The study was performed at a temperature of 20°C. The test system included control, test chemical and reference substance. Polyseed were used as a test inoculum for the study. The concentration of test and reference chemical (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 chemical) was also calculated using BOD & ThOD and was determined to be 66.26%. Degradation of Sodium Benzoate exceeds 70.48% on 7 days & 73.49% on 14th day. The activity of the inoculum is thus verified and the test can be considered as valid. The BOD42 value of test chemical was observed to be 0.4 mgO2/mg. ThOD was calculated as 1.02 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 39.21%. Based on the results, the test chemical, under the test conditions, was considered to be inherently biodegradable in nature.