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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 F (Ready Biodegradability: Manometric Respirometry Test)
Principles of method if other than guideline:
Biodegradation study was conducted according to OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test) for evaluating the percentage biodegradability of test chemical.
GLP compliance:
no
Oxygen conditions:
aerobic
Inoculum or test system:
other: mixture of domestic waste water, surface soil and soil samples
Details on inoculum:
Mixed Inoculum Preparation (In-House): Domestic waste water, surface soil and soil samples from polluted sites receiving predominantly domestic waste was collected and were mixed to get diluted suspension. The inoculum was kept aerobic until being used for experiment by supplying organic and inorganic sources required by micro flora to sustain at controlled laboratory conditions. This gave the bacterial count as 10E7to 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.:
100 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
other: BOD and ThOD
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 Respirometer BOD Sensor System (Code: F102B0133; non-automatic pressure measurement sensor system) and Respirometric incubator (FOC 120i)) by VELP Scientifica.

CONTROL AND BLANK SYSTEM
- Inoculum blank: it contains only test inoculum
- Procedure control: contains reference compound and inoculum
Reference substance:
other: Sodium Benzoate
Parameter:
other: BOD and ThOD
Value:
53.6
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 0.648 mgO2/mg. ThoD was determined by calculation as 1.209 mgO2/mg. % Degradation was calculated using the values of BOD and ThOD for test item and was determined to be 53.60 %. The % degradation of procedure control (Sodium Benzoate) was also calculated using BOD & ThOD and was found to be 75.20 %. The mean BOD values (mg O2/l) in control on 28th day was 1.252 mg O2/l, thereby fulfilling the control validity criteria (i.e., the oxygen consumption of the inoculum blank is normally 20-30 mg O2/l and should not be greater than 60 mg/l in 28 days). Degradation of Sodium Benzoate exceeds 65.65 %after 7 days and 69.79 % after 14 days.The activity of the inoculums is thus verified and the test can be considered as valid.
Results with reference substance:
The % degradation of procedure control (Sodium Benzoate) was also calculated using BOD & ThOD and was found to be 74.074%. The mean BOD values (mg O2/l) in control on 28th day was 9 mg O2/l, thereby fulfilling the control validity criteria (i.e., The oxygen consumption of the inoculum blank is normally 20-30 mg O2/l and should not be greater than 60 mg/l in 28 days). Degradation of Sodium Benzoate exceeds 50.050 %after 7 days and 68.068 % after 14 days. The activity of the inoculums is thus verified and the test can be considered as valid.

TABLE 1

RESPIROMETRIC VALUES(oxygen consumed mg O2/l)

 

No. of Days

Inoculum Blank

(Control)

Test Suspension

Procedure Control (Reference Item)

1

5.4

14

31.5

2

8.2

15

71.5

3

13.7

28

101.5

4

14.2

28

112

5

14.7

29

116.5

6

14.2

29

122.5

7

14.7

29

124

8

14.2

26

124.5

9

14.2

26

127

10

14.7

28

128.5

11

14.7

26

128.5

12

14.7

28

131

13

14.7

28

131.5

14

15.3

28

131.5

15

15.3

29

133

16

14.7

26

134.5

17

14.7

28

135.5

18

15.8

31

135.5

19

15.8

31

135.5

20

15.3

31

135.5

21

15.3

29

137.5

22

15.8

32

137.5

23

15.8

31

138.5

24

15.8

32

139.5

25

15.8

32

139.5

26

15.8

32

139.5

27

15.8

31

139.5

28

15.8

31

141

TABLE 2

BOD values (mgO2/mg)

No. of Days

Test Suspension

Procedure Control (Reference Item)

1

0.344

0.261

2

0.272

0.633

3

0.572

0.878

4

0.552

0.978

5

0.572

1.018

6

0.592

1.083

7

0.572

1.093

8

0.472

1.103

9

0.472

1.128

10

0.532

1.138

11

0.452

1.138

12

0.532

1.163

13

0.532

1.168

14

0.508

1.162

15

0.548

1.177

16

0.452

1.198

17

0.532

1.208

18

0.608

1.197

19

0.608

1.197

20

0.628

1.202

21

0.548

1.222

22

0.648

1.217

23

0.608

1.227

24

0.648

1.237

25

0.648

1.237

26

0.648

1.237

27

0.608

1.237

28

0.608

1.252

TABLE 3

PERCENT BIODEGRDATION RESULTS

No. of Days

Test Suspension

Procedure Control (Reference Item)

1

28.45

15.68

2

22.50

38.02

3

47.31

52.73

4

45.66

58.74

5

47.31

61.14

6

48.97

65.05

7

47.31

65.65

8

39.04

66.25

9

39.04

67.75

10

44.00

68.35

11

37.39

68.35

12

44.00

69.85

13

44.00

70.15

14

42.02

69.79

15

45.33

70.69

16

37.39

71.95

17

44.00

72.55

18

50.29

71.89

19

50.29

71.89

20

51.94

72.19

21

45.33

73.39

22

53.60

73.09

23

50.29

73.69

24

53.60

74.29

25

53.60

74.29

26

53.60

74.29

27

50.29

74.29

28

50.29

75.20

Table 4

BOD28, THOD AND % BIODEGRADATION VALUES

MeThOD details

BOD28(mgO2/mg)

ThOD (mgO2/mg)

% Biodegradation

Test Item

0.648

1.209

53.60

Reference Item

1.252

1.665

75.20

Validity criteria fulfilled:
yes
Interpretation of results:
inherently biodegradable
Conclusions:
The test chemical undergoes 53.60 % biodegradation after 28 days in the test condition. Thus, the test item can be considered as ultimate inherently biodegradable.
Executive summary:

28-days Manometric respirometry test was perrformed following the OECD guideline 301F to determine the ready biodegradability of the test chemical. The study was performed at a temperature of 20± 1°C. Mixture of domestic waste water, surface soil and soil samples was used as a test inoculum for the study. This inoculum was collected and were mixed to get diluted suspension. The inoculum was kept aerobic until being used for experiment by supplying organic and inorganic sources required by micro flora to sustain at controlled laboratory conditions.  This gave the bacterial count as 10E7to 10E8 CFU/ml. At the regular interval microbial plating was also performed on agar to confirm the vitality and CFU count of microorganism. OECD mineral medium was used for the study. 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 100 mg/L, while that of inoculum was 10 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 % degradation of procedure control (Sodium Benzoate) was also calculated using BOD & ThOD and was determined to be 75.20 %. The mean BOD values (mg O2/l) in control on 28th day was 1.252 mg O2/l, thereby fulfilling the control validity criteria (i.e., The oxygen consumption of the inoculum blank is normally 20-30 mg O2/l and should not be greater than 60 mg/l in 28 days). Degradation of Sodium Benzoate exceeds 65.65 %after 7 days and 69.79 % after 14 days. The activity of the inoculums is thus verified and the test can be considered as valid. The BOD28 value of test chemical was observed to be 0.648 mgO2sup>/mg. ThOD was calculated as 1.209 mgO2/mg. Accordingly, the % degradation of the test item after 28 days of incubation at 20 ± 1°C according to manometric respirometry test was determined to be 53.60 %.Based on the results, the test item, under the test conditions, was considered to be ulimate inherently biodegradable at 20 ± 1°C over a period of 28 days.

Description of key information

The test chemical undergoes 53.60 % biodegradation after 28 days in the test condition. Thus, the test item can be considered as ultimate inherently biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
inherently biodegradable

Additional information

Various experimental key and supporting studies for the target compound1,2-Benzisothiazol-3(2H)-one 1,1-dioxide, sodium salt(CAS No. 128-44-9) were reviewed for the biodegradation end point which are summarized as below

 

In first experimental study the 28-days Manometric respirometry test was performed following the OECD guideline 301F to determine the ready biodegradability of the test chemical. The study was performed at a temperature of 20± 1°C. Mixture of domestic waste water, surface soil and soil samples was used as a test inoculum for the study. This inoculum was collected and was mixed to get diluted suspension. The inoculum was kept aerobic until being used for experiment by supplying organic and inorganic sources required by micro flora to sustain at controlled laboratory conditions.  This gave the bacterial count as 10E7to 10E8 CFU/ml. At the regular interval microbial plating was also performed on agar to confirm the vitality and CFU count of microorganism. OECD mineral medium was used for the study. 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 100 mg/L, while that of inoculum was 10 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 % degradation of procedure control (Sodium Benzoate) was also calculated using BOD & ThOD and was determined to be 75.20 %. The mean BOD value (mg O2/l) in control on 28th day was 1.252 mg O2/l, thereby fulfilling the control validity criteria (i.e., The oxygen consumption of the inoculum blank is normally 20-30 mg O2/l and should not be greater than 60 mg/l in 28 days). Degradation of Sodium Benzoate exceeds 65.65 %after 7 days and 69.79 % after 14 days. The activity of the inoculums is thus verified and the test can be considered as valid. The BOD28 value of test chemical was observed to be 0.648 mgO2sup>/mg. ThOD was calculated as 1.209 mgO2/mg. Accordingly, the % degradation of the test item after 28 days of incubation at 20 ± 1°C according to manometric respirometry test was determined to be 53.60 %.Based on the results, the test item, under the test conditions, was considered to be ulimate inherently biodegradable at 20 ± 1°C over a period of 28 days.

Another experimental study was performed in this study 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 for this study. 1 polyseed capsule were 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. 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 73.49  %. Degradation of Sodium Benzoate exceeds 39.15 % on 7 days & 61.44 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 1.12 mgO2/mg. ThOD was calculated as 1.17 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 96.55 %. Based on the results, the test item, under the test conditions, was considered to be readily biodegradable in nature.

Last experimental study was reviewed from peer reviewed journal(Jitendra R. Harjani, et. al; 2009) in this study theBiodegradation experiment was conducted for 28 days for evaluating the percentage biodegradability of test substance. The study was performed according to OECD Guideline 310 (Ready Biodegradability - CO2 in Sealed Vessels (Headspace Test).This method allows the evaluation of the ultimate aerobic biodegradability of an organic compound in an aqueous medium at a given concentration of microorganisms by analysis of inorganic carbon. Activated sludge was used as a test inoculums collected from an activated sludge treatment plant. Initial test substance conc. used in the study was 40 mg/l. The test chemical as the sole source of carbon and energy was added at a concentration of 40 mg/l to a mineral salt medium. These solutions were inoculated with activated sludge, washed and aerated prior to use and incubated in sealed vessels with a headspace of air. Biodegradation (mineralization to carbon dioxide) was determined by measuring the net increase in the total organic carbon (TOC) levels over time compared with unamended blanks. The test ran for 28 days. The extent of biodegradation was expressed as a percentage of the theoretical amount of inorganic carbon (ThIC) based on the amount of test compound. Sodiumn-dodecyl sulfate (SDS) was used as a reference substance for the study. Test chemical undergoes 41% degradation by TOC removal parameter in 28 days. It is noted that chemical has reached its highest level of biodegradability within 14 days of incubation, which has been associated with very high rates of biodegradation of the saccharin anion. Thus, based on percentage degradation, test chemical is considered to be inherently biodegradable in nature.

On the basis of above results from experimental studies for target chemical1,2-Benzisothiazol-3(2H)-one 1,1-dioxide, sodium salt(from study report and peer reviewed journal), it can be concluded that the test substance1,2-Benzisothiazol-3(2H)-one 1,1-dioxide, sodium saltcan be expected to beinherentlybiodegradable in nature.