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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:
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:
other: Sodium Benzoate
Parameter:
% degradation (O2 consumption)
Value:
60
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 1.02 mgO2/mg. ThOD was determined by calculation as 1.7 mgO2/mg. % degradation was calculated using the values of BOD and ThOD for test item and was determined to be 60 % at 20 ± 1°C. The % degradation of procedure control (reference item) was also calculated using BOD & ThOD and was determined to be 69.27 %. Degradation of Sodium Benzoate exceeds 64.46 % on 7 days & 75.3 % 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 69.27 %. Degradation of Sodium Benzoate exceeds 64.46 % on 7 days & 75.3 % 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

6.6

6.2

6.5

7

6.4

4.4

2

14

6.1

2.3

1

21

5.8

1.6

0.4

28

5.6

1.2

0.2

35

5.2

0.4

0.1

42

4.8

0.3

0.1

 

TABLE 2

BOD values (mgO2/mg)

No. of Days

 

Test Suspension

Procedure Control

(Reference Item)

7

0.4

1.07

14

0.85

1.25

21

0.95

1.32

28

1

1.32

35

1.1

1.25

42

1.02

1.15

 

TABLE 3

PERCENT BIODEGRDATION RESULTS

No. of Days

 

Test Suspension

Procedure Control

(Reference Item)

0

0%

0%

7

23.53%

64.46%

14

50%

75.3%

21

55.88%

79.52%

28

58.82%

79.51%

35

64.7%

75.3%

42

60%

69.27%

 

Table 4

BOD42, THOD AND % BIODEGRADATION VALUES

 

Method details

BOD42 (mgO2/mg)

ThOD (mgO2/mg)

% Biodegradation

 

Test Item

1.02

1.7

60

Reference Item

1.15

1.66

69.27

 

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The test chemical undergoes 60 % biodegradation after 42 days in the test condition. Thus, the test item was considered to be readily biodegradable.
Executive summary:

42-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 inoculum at concentration 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. .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 69.27 %. Degradation of Sodium Benzoate exceeds  64.46 % 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 BOD42 value of test chemical was observed to be 1.02 mgO2/mg. ThOD was calculated as 1.7 mgO2/mg. Accordingly, the % degradation of the test item after 42 days of incubation at 20 ± 1°C according to Closed Bottle test was determined to be 60 %. Based on the results, the test item, under the test conditions, was considered to be readily biodegradable in nature.

Description of key information

42-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 inoculum at concentration 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. .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 69.27 %. Degradation of Sodium Benzoate exceeds  64.46 % 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 BOD42 value of test chemical was observed to be 1.02 mgO2/mg. ThOD was calculated as 1.7 mgO2/mg. Accordingly, the % degradation of the test item after 42 days of incubation at 20 ± 1°C according to Closed Bottle test was determined to be 60 %. 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

Experimental studies have reviewed from differents sources for biodegradation in water endpoint and their results are summarized below.

The first study was reviewed fro study report in this study the 42-days Closed Bottle test was performed 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 inoculum at concentration 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. .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 69.27 %. Degradation of Sodium Benzoate exceeds  64.46 % 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 BOD42 value of test chemical was observed to be 1.02 mgO2/mg. ThOD was calculated as 1.7 mgO2/mg. Accordingly, the % degradation of the test item after 42 days of incubation at 20 ± 1°C according to Closed Bottle test was determined to be 60 %. Based on the results, the test item, under the test conditions, was considered to be readily biodegradable in nature.

Next experimental study was reviewed from authoritative database (J check) in this study the Biodegradation experiment was conducted for 28 days for evaluating the percentage biodegradability of test substance. Concentration of inoculum i.e, sludge used was 30 mg/l and initial test substance conc. used in the study was 100 mg/l, respectively. The percentage degradation of test substance was determined to be 0 and 4% degradation by BOD and GC parameter in 28 days. Thus, based on percentage degradation is considered to be not readily biodegradable in nature.

Last study was reviewed from peer reviewed journal in this Biodegradation experiment was conducted according to OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I)) for evaluating the percentage biodegradability of test substance . Initial test substance conc. used in the study was 20 mg/l. Namely, a water, acetone or DMSO solution (0.1 ml) of the test chemicals was added to a mixture of river/sea water (4.9 ml) from an unpolluted area and an autoclaved solution (5.0ml) of 0.2% peptone in a sterile test tube with a tight plug. After sealed with film and fixed at an angle of 30°in a dark box, the test tubes were incubated at 30°C and shaked at 120 rpm. Inoculum used for the study was mixed culture obtained from different sources (Sea water from Enoshima Beach and River water from Tama River). The percentage degradation of test substance in both river and sea water was determined to be 5 and 6% by BOD parameter in 3 days. Thus, based on percentage degradation, is considered to be not readily biodegradable in nature.

By considering results of all the studies mentioned above it was observed that last two studies are showing that test chemical is not readily biodegradable.Since in second study guideline is not mentioned and in third study the duration of sudy was very less therefore reults of first study has been considered and according to it test chemical is readily biodegradable.