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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
Study period:
19 July 2017 - 16 August 2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Remarks:
Copy of the GLP Certificate attached in the study report
Oxygen conditions:
aerobic
Inoculum or test system:
sewage, domestic (adaptation not specified)
Details on inoculum:
The test system was a microbial inoculum of good quality, collected from a sewage plant for domestic sewage. The sludge was allowed to settle and then aerated until use.
Duration of test (contact time):
> 0 - <= 28 d
Initial conc.:
>= 2.2 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
The biodegradation was followed by the oxygen uptake of the microorganisms during exposure.
Adequate amount of the stock solutions were combined and filled up with deionised water to the appropriate final volume (ratio of composition referring to 1 mL of the stock solutions) filled up with deionised water to a final volume of 1000 mL according to the guideline). The test medium was aerated for 20 minutes and allowed to stand for about 20 hours at the test temperature. The dissolved oxygen concentration was 8.5 mg/L at about 22 °C.
Reference substance:
other: Sodium Benzoate
Preliminary study:
The chosen test item concentration was based on the measured chemical oxygen demand (COD): 2.67 ±0.020 mg O2/mg test item and on the performed 14-d preliminary test.
Key result
Parameter:
% degradation (O2 consumption)
Value:
ca. 26.4
Sampling time:
28 d
Details on results:
Under the test conditions the percentage biodegradation of Tar, Pinus sylvestris reached a mean of 26.4 % after 28 days based on the measured COD of the test item. According to the test guidelines the pass level for ready biodegradability is removal of 60 % COD/ThOD.

Percentage Biodegradation at Different Time Intervals during the Exposure Period of 28 Days

Treatment

Concentration

Flask

Percent of biodegradation after n days of exposure

 

[mg/L]

No.

7

14

21

28

Test item

 

1a

11.9

22.1

21.3

26.4

2.2

1b

17.0

23.8

23.0

26.4

 

mean

14.5

23.0

22.1

26.4

Reference item

 

2a

68.3

68.3

74.2

82.5

3.6

2b

68.3

68.3

77.5

84.2

 

mean

68.3

68.3

75.8

83.3

Toxicity control

Test item: 2.2
Reference item: 3.6

4a

36.6

36.6

35.4

38.6

4b

37.4

36.6

34.6

37.8

mean

37.0

36.6

35.0

38.2

Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
Under the test conditions the percentage biodegradation of Tar, Pinus sylvestris reached a mean of 26.4 % after 28 days based on the measured COD of the test item. According to the test guidelines the pass level for ready biodegradability is removal of 60 % COD/ThOD. Therefore the test item is considered not readily biodegradable.
Executive summary:

The test item Tar, Pinus sylvestris was investigated for its ready biodegradability in a Closed Bottle Test over a period of 28 days. The biodegradation was followed by the oxygen uptake of the microorganisms during exposure. As a reference item Sodium benzoate was tested simultaneously under the same conditions as the test item, and functioned as a procedure control. Under the test conditions the percentage biodegradation of Tar, Pinus sylvestris reached a mean of 26.4 % after 28 days based on the measured COD of the test item.

Description of key information

Under the test conditions the percentage biodegradation of Tar, Pinus sylvestris reached a mean of 26.4 % after 28 days based on the measured COD of the test item. According to the test guidelines the pass level for ready biodegradability is removal of 60 % COD/ThOD. Therefore, the test item is not readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
inherently biodegradable

Additional information