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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
Study period:
January 09, 2019 to February 15, 2019
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Version / remarks:
1992
Deviations:
no
GLP compliance:
yes (incl. certificate)
Oxygen conditions:
aerobic
Inoculum or test system:
sewage, domestic, non-adapted
Details on inoculum:
Preparation of Inoculum
The secondary effluent of a treatment plant (Jin-ju munsan public sewage treatment facility, Republic of Korea) was used as the inoculum. After collection, it was kept aerobic during transport and coarse particles were removed by settling for 1 hour. The inoculum was pre-conditioned by aerating for 7 days at the test temperature (22±2˚C).

Preparation of Mineral Medium
The stock solutions for mineral medium were prepared acc. to the guideline.
Deionized water was sterilized by autoclaving for 15 minutes at 121˚C.

Interpretation of results
If the percentage degradation of the test item is more than 60% by BOD measurement within 28 days, the test item is regarded as readily biodegradation. This level must be reached within 10 days of biodegradation exceeding 10%.
Duration of test (contact time):
>= 1 - <= 28 d
Initial conc.:
>= 99.7 - <= 100.2 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
Preparation of Test Bottles & Test Conditions
Test bottles (500 mL-BOD bottles, WTW), all glassware and associated materials used in this test were sterilized by autoclaving for 15 minutes at 121˚C. The amounts of test item, reference item and mercury(II) chloride were directly weighed into the test bottles. The sodium hydroxide (two tablets) was used to absorb the carbon dioxide formed by the microorganisms, and test bottles were tightly sealed with the OxiTop®-C measuring heads. All procedures for preparation of test bottles were carried out in the clean bench to maintain sterile condition.
The test bottles were placed in a completely dark, temperature-controlled incubation under continuous stirring on inductive stirring system (Oxitop® Control, WTW).
Test bottles were prepared as follows: A volume of 10.0 mL inoculum equivalent to about 61.0 mL/L was added to the all test bottles except for bottle 6 (abiotic sterile control). Finally, the test bottles were made up to 164 mL with mineral medium prepared. The BOD values of all test bottles determined by OxiTop® controller (WTW) were measured automatically over a period of 28 days at 22.0±2.0˚C and test temperature were recorded daily during the test period. At the end of incubation (28 days), the pH of all test bottles was measured and recorded.

Interpretation of results
If the percentage degradation of the test item is more than 60% by BOD measurement within 28 days, the test item is regarded as readily biodegradation. This level must be reached within 10 days of biodegradation exceeding 10%.
Reference substance:
benzoic acid, sodium salt
Test performance:
Test Conditions
The test temperature was maintained at 21.7±0.08˚C over a period of 28 days, and the pH value of the test suspensions (bottle 1, 2) was 7.5 at the end of the test, respectively. Test conditions were maintained within the acceptable limit and met the test guideline recommendations.
Key result
Parameter:
% degradation (O2 consumption)
Value:
>= 89.5 - <= 92.5
St. dev.:
2.1
Sampling time:
28 d
Details on results:
Microbial Degradation of Reference Item and Test Item
The results of the BOD concentrations and the percentage microbial degradation of the reference, and the test item over a period of 28 days are are presented in any other information on results.

In the procedure control, the percentage microbial degradation of the reference item was 86.1% at 14 days, thus confirming suitability of the inoculum.

The percentage microbial degradation of the toxicity control containing both the test item and the reference item was 70.6% at 14 days. This result confirms that the test item was not inhibitory to the activity of the microbial inoculum, because the percentage degradation in the toxicity control was more than 25% within 14 days.

In the inoculum blank, the BOD concentrations ranged from 0.0 to 16.9 mgO2/L within 28 days, indicating this value was within the acceptable range (less than 60 mgO2/L) specified by the test guidelines.

In the test suspensions, on the basis of the mean value, the 10-day window began at 1.6 days and the percentage microbial degradation of the test item at the end of the 10-day window (11.6 days) was 84.7%. The difference (% CV; Coefficient of Variation) of these values was 0.8 %.

At the end of the 28 days exposure period, the percentage degradation was 91.0% and difference was 2.1%.

The Percentage Microbial Degradation of Test Item and Reference Item by BOD

Time

(days)

% Degradationa)

Test suspensions

Procedure

control

Toxicity control

Bottle 1

Bottle 2

Mean±SDb)

Bottle 5

Bottle 7

0

0.0

0.0

0.0±0.0

0.0

0.0

1

0.0

0.0

0.0±0.0

16.9

14.0

2

15.8

18.8

17.3±2.1

50.5

24.8

3

37.4

40.5

39.0±2.2

57.2

28.0

4

50.4

54.8

52.6±3.1

67.4

34.1

5

59.9

61.3

60.6±1.0

73.2

37.6

6

68.1

65.9

67.0±1.6

76.8

41.4

7

74.3

73.1

73.7±0.8

79.8

44.7

8

76.8

78.7

77.8±1.3

81.6

48.6

9

79.9

81.8

80.9±1.3

83.4

52.5

10

83.0

83.4

83.2±0.3

85.2

57.2

11

83.3

83.7

83.5±0.3

84.3

60.6

12

84.8

86.8

85.8±1.4

84.3

64.5

13

84.8

86.8

85.8±1.4

86.1

66.7

14

86.3

88.3

87.3±1.4

86.1

70.6

15

86.3

88.3

87.3±1.4

86.1

73.1

16

87.9

88.3

88.1±1.4

86.1

74.4

17

87.9

88.3

88.1±0.3

87.9

75.3

18

87.9

89.9

88.9±0.3

87.9

76.9

19

89.4

89.9

89.7±1.4

87.9

77.7

20

89.4

89.9

89.7±0.4

89.1

78.3

21

88.7

90.7

89.7±0.4

88.3

77.9

22

88.7

90.7

89.7±1.4

88.3

79.6

23

90.2

90.7

90.5±0.4

88.3

80.4

24

90.2

90.7

90.5±0.4

88.3

81.2

25

90.2

90.7

90.5±0.4

88.3

81.2

26

90.2

91.7

91.0±1.1

88.3

81.8

27

90.2

91.7

91.0±1.1

88.3

82.6

28

89.5

92.5

91.0±2.1

87.5

83.0

a)     Degradation (%) based on the theoretical oxygen demand

b)    Standard Deviation

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The test item is readily degradable by micro-organisms in the aquatic environmental according to the pass level of biodegradability specified by the guideline, fulfilling all criteria: 91.0±2.1% degradation within 28 days.
Executive summary:

The test item 2,3-butanediol((2R,3R)-rich) was investigated to determine the ready biodegradability over a period of 28 days in accordance with OECD Guidelines (Test No. 301 Ready Biodegradability, 301 F) and in compliance with GLP.

The secondary effluent of a treatment plant (Jin-ju munsan public sewage treatment facility, Republic of Korea) was used as the inoculum. After collection, it was kept aerobic during transport and coarse particles were removed by settling for 1 hour. The inoculum was pre-conditioned by aerating for 7 days at the test temperature (22±2˚C). The initial test item concentration was 100 mg/L (2 replicates) and the concentration of inoculum was 61 mL/L. An inoculum blank (2 replicates), procedure, abiotic and toxicity control (1 replicate) were run in parallel. The BOD values of all test bottles determined by OxiTop® controller (WTW) were measured automatically over a period of 28 days at 22.0±2.0˚C and test temperature were recorded daily during the test period.

The results were as follows: The test temperature during the test period was maintained at 21.7±0.08˚C and the pH values measured in the test suspensions were 7.5 at the end of incubation (28 days), indicating the test conditions were within the acceptable limit. The percentage microbial degradation of the reference item was 86.1% after 14 days, thus confirming suitability of the inoculum. In the toxicity control, the percentage microbial degradation was 70.6% at 14 days, thus it was confirmed that the test item had obviously no inhibitory effect on the activity of the inoculum. In the test suspensions, the percentage microbial degradation of the test item was 84.7% at the end of the 10-d window (after 11.6 days) and was 91.0% at end of the test (28 days). The pass level for ready biodegradability is 60% of ThOD, which has to be reached in a 10-day window within 28 days period of the test.

Therefore, 2,3-butanediol((2R,3R)-rich) was classified as readily degradable by micro-organisms in the aquatic environmental according to the pass level of biodegradability specified by the OECD 301F (1992).

Description of key information

Readily biodegradable by micro-organisms, fulfilling all criteria: 91.0±2.1% degradation within 28 days.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable
Type of water:
freshwater

Additional information

In the reliable key study, the test item 2,3 -butanediol((2R,3R)-rich) was investigated to determine the ready biodegradability over a period of 28 days in accordance with OECD Guidelines (Test No. 301 Ready Biodegradability, 301 F) and in compliance with GLP. The secondary effluent of a treatment plant (Jin-ju munsan public sewage treatment facility, Republic of Korea) was used as the inoculum. After collection, it was kept aerobic during transport and coarse particles were removed by settling for 1 hour. The initial test item concentration was 100 mg/L (2 replicates) and the concentration of inoculum was 61 mL/L. An inoculum blank (2 replicates), procedure, abiotic and toxicity control (1 replicate) were run in parallel.

The results were as follows: The percentage microbial degradation of the reference item was 86.1% after 14 days, thus confirming suitability of the inoculum. In the toxicity control, the percentage microbial degradation was 70.6% at 14 days, thus it was confirmed that the test item had obviously no inhibitory effect on the activity of the inoculum. In the test suspensions, the percentage microbial degradation of the test item was 84.7% at the end of the 10-d window (after 11.6 days) and was 91.0% at end of the test (28 days).

Therefore, 2,3-butanediol((2R,3R)-rich) was classified as readily degradable by micro-organisms in the aquatic environmental according to the pass level of biodegradability specified by the OECD 301F (1992).