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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
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):
28 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:
74.85
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 1.25 mgO2/mg. ThOD was determined by calculation as 1.67 mgO2/mg. % degradation was calculated using the values of BOD and ThOD for test item and was determined to be74.85 % at 20 ± 1°C. The % degradation of procedure control (reference item) was also calculated using BOD & ThOD and was determined to be 78.31 %. Degradation of Sodium Benzoate exceeds 43.37 % on 7 days & 61.44 % 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 78.31 %. Degradation of Sodium Benzoate exceeds 43.37 % on 7 days & 61.44 % 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

6.5

6.5

7

6.6

5

3.4

14

6.5

3.7

2.1

21

6.2

2.9

1.8

28

6

0.7

0.5

 

TABLE 2

BOD values (mgO2/mg)

No. of Days

 

Test Suspension

Procedure Control

(Reference Item)

0

0

0

7

0.32

0.72

14

0.62

1.02

21

0.75

1.02

28

1.25

1.3

 

TABLE 3

PERCENT BIODEGRDATION RESULTS

No. of Days

 

Test Suspension

Procedure Control

(Reference Item)

0

0%

0%

7

19.16%

43.37%

14

37.12%

61.44%

21

41.91%

61.44%

28

74.85%

78.31%

 

Table 4

BOD28, THOD AND % BIODEGRADATION VALUES

Method details

 

BOD28 (mgO2/mg)

ThOD (mgO2/mg)

% Biodegradation

TestItem

1.25

1.67

74.85

ReferenceItem

1.3

1.6

78.31

 

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The test chemical undergoes 74.85 % biodegradation after 28 days in the test condition. Thus, the test chemical was considered to be readily biodegradable.
Executive summary:

28-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 . The concentration of test and reference item (Sodium Benzoate) chosen for both the study was 4 mg/L, while that of inoculum was 32ml/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 78.31 %. Degradation of Sodium Benzoate exceeds 43.37 % 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 1.25 mgO2/mg. ThOD was calculated as 1.67 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 74.85 %. Based on the results, the test item, under the test conditions, was considered to be readily biodegradable in nature.

Description of key information

28-days Closed Bottle test following the OECD guideline 301 D was performed 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 . The concentration of test and reference item (Sodium Benzoate) chosen for both the study was 4 mg/L, while that of inoculum was 32ml/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 78.31 %. Degradation of Sodium Benzoate exceeds 43.37 % 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 1.25 mgO2/mg. ThOD was calculated as 1.67 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 74.85 %. 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

Different experimental studies have been reviewed from study report and peer reviewed journal for Biodegradation in water endpoint and their results are summarized below.

 

In first study the 28-days Closed Bottle test following the OECD guideline 301 D was performed 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 . The concentration of test and reference item (Sodium Benzoate) chosen for both the study was 4 mg/L, while that of inoculum was 32ml/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 78.31 %. Degradation of Sodium Benzoate exceeds 43.37 % 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 1.25 mgO2/mg. ThOD was calculated as 1.67 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 74.85 %. Based on the results, the test item, under the test conditions, was considered to be readily biodegradable in nature.

 

 

Another study was reviewed from authoritative database ( J check) in this percent degradation of test chemical was determined by using various parameters and activated sludge at concentration 30 mg/L concentration as inoculum and initial test chemical concentration used was 100 mg/L for 28 days.

The percent degradation of test chemical in 28 days was observed to be 56.2% and 53 % by O2 consumption (BOD) parameter  in the case where TOD is calculated by assuming n = 4 and n=10 respectively, by using parameter TOC removal test chemical showed 52.2 % degradation and by using test material analysis parameter (UV-Vis) percent degradation observed was 43.1.

By considering all the percent degradation value by various parameters it is concluded that test chemical is Ultimate inherently biodegradable in water.

 

Next study was reviewed from chemosphere Journal (1989) in this study an experiment was performed to determine percent degradation of test chemical by using sludge from the anaerobic digester of a sewage treatment plant treating predominantly domestic sewage as inoculum , mineral salt was used as medium and Oxygen was removed by sparging with pure nitrogen before use. The initial test chemical concentration used was 60 mg/L. Percent degradation of test chemical was observed to be 86 and 82 % by Gas production (theoretical and observed carbon dioxide and methane gas production ratios) as parameter in anaerobic condition in 37 days. BY considering percent degradation value it is concluded that test chemical is readily biodegradable.

 

Last study was also reviewed from chemosphere journal (1996) in this publication an experiment was performed to determine biodegradation potential of test chemical by using CO2 evolution as parameter. In this fortified BOD medium was used and bottle was connected CO2-free air apparatus. The test bottles were placed on a rotary shaker at room temperature and aerated overnight with agitation to purge the system of background CO2. After overnight aeration, the Ba(OH)2 traps were connected to the test system. The appropriate amount of test substance (20-40 mg/L) was added to the test bottles a 1% v/v (10 ml/L) activated sludge inoculum. The percent degradation of test chemical was determined to be 80% in days by considering CO2 evolution as parameter and activated sludge was used as inoculums. By considering this percent degradation value it is concluded that test chemical is readily biodegradable in water.

 

By considering results of all the studies mentioned above it is concluded that test chemical is readily biodegradable in nature.