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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:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
data from handbook or collection of data
Remarks:
experimental data of read across substances
Justification for type of information:
Data for the target chemical is summarized based on the structurally similar read across chemicals
Reason / purpose for cross-reference:
read-across source
Reason / purpose for cross-reference:
read-across source
Reason / purpose for cross-reference:
read-across source
Qualifier:
according to guideline
Guideline:
other: as mentioned below
Principles of method if other than guideline:
WoE report is based on three biodegradation studies as-
WoE 2., WoE 3 and WoE 4.
GLP compliance:
not specified
Oxygen conditions:
aerobic
Inoculum or test system:
other: WoE 2 and WoE 3: Mixed inoculum, WoE 4: activated sludge, non-adapted
Details on inoculum:
WoE 2 and WoE 3: 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.

WoE 4: - Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Test inoculum (Activated sludge – non-adapted) was obtained from a domestic sewage treatment plant at the ARA Basel Industry.
- Concentration of sludge: 1000 mg/l
Duration of test (contact time):
28 d
Initial conc.:
4 mg/L
Based on:
test mat.
Remarks:
WoE 2 and WoE 3
Initial conc.:
150 mg/L
Based on:
DOC
Remarks:
WoE 4
Parameter followed for biodegradation estimation:
O2 consumption
Remarks:
WoE 2 and WoE 3
Parameter followed for biodegradation estimation:
DOC removal
Remarks:
WoE 4
Details on study design:
WoE 2 and WoE 3:
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

WoE 4:
TEST CONDITIONS
- Composition of medium: Test medium was prepared according to the specification of the EEC L133 (pp. 99-105), volume 31 resp. OECD Method 302B.
- Test temperature: 22±3°C
- Continuous darkness: no
- Other: Test was performed under indirect daylight.

TEST SYSTEM
- Number of culture flasks/concentration: Duplicates

TEST SYSTEM
- Measuring equipment: A Shimadzu TOC-500 analyzer was used to determine the TOC.
Reference substance:
benzoic acid, sodium salt
Remarks:
WoE 2 and WoE 3
Reference substance:
diethylene glycol
Remarks:
WoE 4
Parameter:
% degradation (O2 consumption)
Value:
> 90.9 - < 92.02
Sampling time:
28 d
Remarks on result:
other: WoE 2 and WoE 3
Parameter:
% degradation (DOC removal)
Value:
98.8
Sampling time:
28 d
Remarks on result:
other: WoE 4
Details on results:
WoE 2: 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 0.9 mgO2/mg. ThOD was determined by calculation as 0.99 mgO2/mg. % degradation was calculated using the values of BOD and ThOD for test item and was determined to be 90.9% 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 54.21% on 7 days & 75.3% on 14th day. The activity of the inoculum is thus verified and the test can be considered as valid.

WoE 3: 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 1.27 mgO2/mg. ThOD was determined by calculation as 1.38 mgO2/mg. % degradation was calculated using the values of BOD and ThOD for test chemical and was determined to be 92.02% at 20 ± 1°C. The % degradation of procedure control (reference item) was also calculated using BOD & ThOD and was determined to be 85.54%. Degradation of Sodium Benzoate exceeds 67.46% on 7 days & 73.49% on 14th day. The activity of the inoculum is thus verified and the test can be considered as valid.

WoE 4: Test substance undergoes 98.8% degradation by DOC removal parameter in 28 days.
Results with reference substance:
WoE 2: 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 54.21% on 7 days & 75.3% on 14th day. The activity of the inoculum is thus verified and the test can be considered as valid.

WoE 3: The % degradation of procedure control (reference item) was also calculated using BOD & ThOD and was determined to be 85.54%. Degradation of Sodium Benzoate exceeds 67.46% on 7 days & 73.49% on 14th day. The activity of the inoculum is thus verified and the test can be considered as valid.

WoE 4: Reference substance diethylene glycol undergoes degradation at 5, 7, 9 and 21 days with a percentage degradation of 10.2%, 49.5%, 96.7% and 98.8%, respectively.

WoE 2:

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

No. of Days

Inoculum Blank

(Control)

Test Suspension

Procedure Control

(Reference Item)

0

7

6.7

6.8

7

6.8

3.7

3

14

6.6

3.1

1.4

21

6.4

2.7

1

28

6.1

2.19

0.6

TABLE 2: BOD Values (mg O2/mg)

 

No. of Days

Test Suspension

Procedure Control

(Reference Item)

0

0

0

7

0.7

0.9

14

0.8

1.25

21

0.85

1.3

28

0.9

1.32

 

TABLE 3: PERCENT BIODEGRDATION RESULTS

No. of Days

Test Suspension

Procedure Control

(Reference Item)

0

0%

0%

7

70.7%

54.21%

14

80.8%

75.3%

21

85.85%

78.31%

28

90.9%

79.51%

 

Table 4: BOD28, THOD AND % BIODEGRADATION VALUES

 

Method details

BOD28 (mgO2/mg)

ThOD (mgO2/mg)

%Biodegradation

Test Item

0.90

0.99

90.9

Reference Item

1.32

1.66

79.51

WoE 3:

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

 

No. of Days

Inoculum Blank

(Control)

Test Suspension

Procedure Control

(Reference Item)

0

8.4

8.1

8.4

7

8

5.2

3.5

14

7.7

4.5

2.8

21

7.4

2.9

2

28

7.1

1.8

1.4

TABLE 2: BOD Values (mg O2/mg)

 

No. of Days

Test Suspension

Procedure Control

(Reference Item)

0

0

0

7

0.67

1.12

14

0.77

1.22

21

1.1

1.35

28

1.27

1.42

 

TABLE 3: PERCENT BIODEGRDATION RESULTS

No. of Days

Test Suspension

Procedure Control

(Reference Item)

0

0%

0%

7

48.91%

67.46%

14

55.79%

73.49%

21

79.71%

81.32%

28

92.02%

85.54%

 

Table 4: BOD28, THOD AND % BIODEGRADATION VALUES

 

Method details

BOD28(mgO2/mg)

ThOD (mgO2/mg)

%Biodegradation

Test Item

1.27

1.38

92.02

Reference Item

1.42

1.66

85.54

WoE 4: no data available

Validity criteria fulfilled:
not specified
Interpretation of results:
readily biodegradable
Conclusions:
On the basis of the experimental studies of the read across chemical and applying the weight of evidence approach, the percentage degradation the test chemical can be expected to be > 90.9% to < 92.02% and 98.8% using O2 consumption and DOC removal parameter in 28 days. Thus, based on percentage degradation, test chemical was considered to be readily biodegradable in water.
Executive summary:

Data available of the structurally and functionally similar read across chemicals has been reviewed to determine the percentage biodegradability of the test chemical. The studies are as mentioned below:

Biodegradation study was conducted for 28-days following the OECD guideline 301 D for determining 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 substance (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 chemical was determined by calculation. % degradation was calculated using the values of BOD and ThOD for test chemical and 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 54.21% on 7 days & 75.3% 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 0.9 mgO2/mg. ThOD was calculated as 0.99 mgO2/mg. Accordingly, the % degradation of the test chemical after 28 days of incubation at 20 ± 1°C according to Closed Bottle test was determined to be 90.9%. Based on the results, the test chemical, under the test conditions, was considered to be readily biodegradable in nature.

Another 28-days Closed Bottle test following the OECD guideline 301 D was conducted for determining the ready biodegradability of the test chemical. The study was performed at a temperature of 20°C and using the same test procedure as mentioned in the above study. The % degradation of procedure control (reference substance) was also calculated using BOD & ThOD and was determined to be 85.54%. Degradation of Sodium Benzoate exceeds 67.46% 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 BOD28 value of test chemical was observed to be 1.27 mgO2/mg. ThOD was calculated as 1.38 mgO2/mg. Accordingly, the % degradation of the test chemical after 28 days of incubation at 20 ± 1°C according to Closed Bottle test was determined to be 92.02%. Based on the results, the test chemical, under the test conditions, was considered to be readily biodegradable in nature.

For the test chemical, biodegradation study was conducted for 28 days for evaluating the percentage biodegradability of test chemical. The study was performed following the OECD Guideline 302 B "Inherent biodegradability: Modified Zahn–Wellens Test" under aerobic conditions. Activated sludge (non-adapted) obtained from a domestic sewage treatment plant at the ARA Basel Industry was used as a test inoculum. Conc. of inoculum and initial test chemical conc. used were 1000 mg/l and 150 mg/l (based on DOC). Test medium was prepared according to the specification of the EEC L133 (pp. 99-105), volume 31 resp. OECD Method 302B. Test was performed in duplicates under indirect daylight condition at 22±3°C. A Shimadzu TOC-500 analyzer was used to determine the TOC. The degradation of test chemical at time t was calculated from the DOC values. Diethylene glycol (158.3 mg/l related to DOC) was used as a reference substance which undergoes degradation at 5, 7, 9 and 21 days with a percentage degradation of 10.2%, 49.5%, 96.7% and 98.8%, respectively. The percentage degradation of test chemical was determined to be 98.8% by using DOC removal parameter in 28 days. Thus, based on percentage degradation, test chemical was considered to be readily biodegradable in water.

On the basis of the experimental studies of the read across chemical and applying the weight of evidence approach, the percentage degradation the test chemical can be expected to be > 90.9% to < 92.02% and 98.8% using O2 consumption and DOC removal parameter in 28 days.  Thus, based on percentage degradation, test chemical was considered to be readily biodegradable in water.

Description of key information

On the basis of the experimental studies of the read across chemical and applying the weight of evidence approach, the percentage degradation the test chemical can be expected to be > 90.9% to < 92.02% and 98.8% using O2 consumption and DOC removal parameter in 28 days. Thus, based on percentage degradation, test chemical was considered to be readily biodegradable in water.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Data available of the structurally and functionally similar read across chemicals has been reviewed to determine the percentage biodegradability of the test chemical. The studies are as mentioned below:

 

Biodegradation study was conducted for 28-days following the OECD guideline 301 D for determining 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 substance (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 chemical was determined by calculation. % degradation was calculated using the values of BOD and ThOD for test chemical and 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 54.21% on 7 days & 75.3% 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 0.9 mgO2/mg. ThOD was calculated as 0.99 mgO2/mg. Accordingly, the % degradation of the test chemical after 28 days of incubation at 20 ± 1°C according to Closed Bottle test was determined to be 90.9%. Based on the results, the test chemical, under the test conditions, was considered to be readily biodegradable in nature.

 

Another 28-days Closed Bottle test following the OECD guideline 301 D was conducted for determining the ready biodegradability of the test chemical. The study was performed at a temperature of 20°C and using the same test procedure as mentioned in the above study. The % degradation of procedure control (reference substance) was also calculated using BOD & ThOD and was determined to be 85.54%. Degradation of Sodium Benzoate exceeds 67.46% 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 BOD28 value of test chemical was observed to be 1.27 mgO2/mg. ThOD was calculated as 1.38 mgO2/mg. Accordingly, the % degradation of the test chemical after 28 days of incubation at 20 ± 1°C according to Closed Bottle test was determined to be 92.02%. Based on the results, the test chemical, under the test conditions, was considered to be readily biodegradable in nature.

 

For the test chemical, biodegradation study was conducted for 28 days for evaluating the percentage biodegradability of test chemical. The study was performed following the OECD Guideline 302 B "Inherent biodegradability: Modified Zahn–Wellens Test" under aerobic conditions. Activated sludge (non-adapted) obtained from a domestic sewage treatment plant at the ARA Basel Industry was used as a test inoculum. Conc. of inoculum and initial test chemical conc. used were 1000 mg/l and 150 mg/l (based on DOC). Test medium was prepared according to the specification of the EEC L133 (pp. 99-105), volume 31 resp. OECD Method 302B. Test was performed in duplicates under indirect daylight condition at 22±3°C. A Shimadzu TOC-500 analyzer was used to determine the TOC. The degradation of test chemical at time t was calculated from the DOC values. Diethylene glycol (158.3 mg/l related to DOC) was used as a reference substance which undergoes degradation at 5, 7, 9 and 21 days with a percentage degradation of 10.2%, 49.5%, 96.7% and 98.8%, respectively. The percentage degradation of test chemical was determined to be 98.8% by using DOC removal parameter in 28 days. Thus, based on percentage degradation, test chemical was considered to be readily biodegradable in water.

 

On the basis of the experimental studies of the read across chemical and applying the weight of evidence approach, the percentage degradation the test chemical can be expected to be > 90.9% to < 92.02% and 98.8% using O2 consumption and DOC removal parameter in 28 days.  Thus, based on percentage degradation, test chemical was considered to be readily biodegradable in water.