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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:
Exposure: 06 Aug 2014 - 03 Sep 2014
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP-guideline study; physico-chemical assay performed parallel to study, but was not performed under GLP
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Qualifier:
according to
Guideline:
ISO DIS 9439 (Ultimate Aerobic Biodegradability - Method by Analysis of Released Carbon Dioxide)
Qualifier:
according to
Guideline:
EPA OPPTS 835.3110 (Ready Biodegradability)
Qualifier:
according to
Guideline:
EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)
GLP compliance:
yes (incl. certificate)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure):
activated sludge was collected from a municipal wastewater treatment plant (Mannheim, Germany) on 04 Aug 2014 from the aeration tank of the plant.
- Pretreatment: activated sludge suspension was aerated with carbon dioxide free air for about 48 hours at 22 ± 2°C. At the day of the exposure the the supension was washed once with drinking water and the aeration was subsequently stopped.
- Concentration of sludge: The sludge of the suspension was adjusted to a concentration of 6.0 g/L of dry weight. Aliquots of 7.5 mL were added
to the test vessels to obtain a sludge concentration of 30 mg/L dry substance in the test assays.
- Water filtered: yes
- Type and size of filter used, if any: sieved by a finely woven mesh (mesh size: 1 mm)
Duration of test (contact time):
28 d
Initial conc.:
10 mg/L
Based on:
other: TOC (applicable to TS1 to TS3)
Initial conc.:
13 mg/L
Based on:
other: test mat. (applicable to TS1 to TS3)
Initial conc.:
9 mg/L
Based on:
other: TOC (applicable to PC1)
Initial conc.:
16 mg/L
Based on:
other: TOC (applicable to PC2)
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Composition of medium: Mineral medium complies with test guideline OECD 301B.
- Test temperature: 22 ± 2°C
- pH adjusted: yes, (final pH of mineral medium = 7.4)

TEST SYSTEM
- Culturing apparatus: 2 L incubation bottles filled up to a volume of 1.5 L
- Number of culture flasks/concentration: 2 blank control assays (BC)
3 test substance assays (TS; test substance only)*
1 inhibition control test assays (IH; test substance + reference substance)
1 reference substance assays (RS; reference substance only)
2 physico-chemical (abiotic) assays (PC; test substance with addition of mercury chloride)

*NOTE: A leakage was observed in the second TS; therefore this test assay was terminated prematurely and excluded from the evaluation of the test result.

Reference substance:
aniline
Parameter:
% degradation (CO2 evolution)
Value:
2
Sampling time:
5 d
Remarks on result:
other: mean value of test substance assay (TS) 1 and 3
Parameter:
% degradation (CO2 evolution)
Value:
19
Sampling time:
8 d
Remarks on result:
other: mean value of test substance assay (TS) 1 and 3
Parameter:
% degradation (CO2 evolution)
Value:
40
Sampling time:
12 d
Remarks on result:
other: mean value of test substance assay (TS) 1 and 3
Parameter:
% degradation (CO2 evolution)
Value:
61
Sampling time:
16 d
Remarks on result:
other: mean value of test substance assay (TS) 1 and 3
Key result
Parameter:
% degradation (CO2 evolution)
Value:
88
Sampling time:
28 d
Remarks on result:
other: mean value of test substance assay (TS) 1 and 3
Details on results:
- Duration of the adaption phase: 6-7 d
- Degree of biodegradation of the test substance at the end of exposure: 80-90% CO2/ThCO2
(ThCO2 = theoretical amount of formed carbon dioxide)
- The physico-chemical controls showed that the substance is stable in water under test conditions without biotic influence.
- Degree of biodegradation of the test substance at the end of the ten-day window: 60-70% CO2/ThCO2
- Degree of DOC removal of the test substance at the end of exposure: 90-100%

NOTE: A leakage was observed in the second of three test assays; therefore this test assay was terminated prematurely and excluded from the evaluation of the test result.
Results with reference substance:
- Degree of biodegradation of the reference substance after 14 d: 65% CO2/ThCO2
- Degree of biodegradation in the inhibition control after 14 d: 40% CO2/ThCO2
(ThCO2 = theoretical amount of formed carbon dioxide)

Biodegradation degree [CO2/ThCO2]

Test

duration

[days]

RS

IH

TS 1

(*)

TS 2

TS 3

TS

mean

value

[TS1/TS3]

0

0

0

0

(*)0

0

0

2

0

0

-1

(*)-1

2

1

5

23

12

-1

(*)-2

5

2

8

29

17

10

(*)12

28

19

12

42

15

27

(*)28

52

40

14

65

40

43

(*)41

61

52

16

70

45

56

(*)49

66

61

19

76

48

67

(*)55

72

70

22

81

52

73

-

78

76

26

84

55

78

-

86

82

28

89

57

84

-

92

88

TS= test substance, TS1 to TS 3 = test substance assays 1 to 3; RS= reference substance; IH= inhibition control

 

Measured DOC values [mg/L]; determined after centrifugation

 

BC 1

BC 2

BC

mean value

RS

IH

TS 1

(*)

TS 2

TS 3

TS

mean

value

[TS1/TS3]

At begin of exposure

a

1.1

1.0

1.1

19.3

18.3

8.9

9.0

7.4

 

b

1.1

1.0

19.6

18.1

9.6

9.7

8.2

At end of exposure

a

0.8

0.8

0.9

1.9

1.1

1.2

-

1.3

b

0.9

0.9

1.8

1.1

1.1

-

1.2

Degree of DOC [%]

95

99

96

-

94

95

TS= test substance; BC= blank control, BC1/BC2 = blank control assays 1 and 2; IH= inhibition control

 

* A leakage was observed at the test vessel of test assay 2 on day 16. Therefore, this test assay was terminated prematurely and excluded from the evaluation of the test result.

 

Determination of the stability of tributylamine respectively, dissolved in test medium based on the test guideline OECD 301B.

Test duration [days]

TOC values [mg/L]

% Change in relation to the TOC at day 0

BC3 a

BC3 b

PC1a

PC1b

PC2a

PC2b

PC1

PC2

0

0.3

0.3

8.1

8.6

16.4

16.8

-

-

2

0.6

0.6

8.4

8.4

16.2

16.8

-3.1

-2.5

5

0.6

0.6

8.0

8.5

16.0

17.0

-5.0

-2.5

8

0.5

0.5

7.4

8.1

16.4

17.8

-9.9

1.8

12

0.5

0.6

8.9

9.1

17.2

17.9

5.0

4.3

14

0.3

0.3

7.8

8.2

16.2

16.9

-4.3

-0.3

16

0.6

0.6

8.2

8.7

16.4

17.3

-2.5

-0.3

19

0.3

0.3

8.0

8.5

15.8

17.3

-1.2

-0.3

22

0.3

0.3

8.6

8.8

16.4

16.2

4.3

-1.8

26

0.5

0.4

8.2

8.5

16.2

16.6

-1.9

-2.1

28

0.3

0.3

8.0

8.4

16.0

17.3

-1.9

0.3

BC3 = blank control 3, PC = physico-chemical control (abiotic control), PC1/PC2 = physico-chemical controls 1 and 2

The stability determination (non-GLP) was performed via TOC measurements of the BC3, PC1 and PC2 assays, while the assays of the GLP study were monitored CO2 evolution and DOC.

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
In a test performed compliant to GLP according to OECD 301B the test item was found to be readily biodegradable (fulfilling 10-day window).
Executive summary:

Tributylamine was tested for ready biodegradability according to OECD 301B. The test was performed compliant to GLP.

The duration of the adaption phase was 6 -7 d. At the end of exposure (after 28 days), the degree of biodegradation of the test substance amounted to 80-90% (mean value: 88%) CO2/ThCO2 (ThCO2 = theoretical amount of formed carbon dioxide). The physico-chemical controls showed that the substance is stable in water under test conditions without biotic influence. The degree of biodegradation of the test substance at the end of the ten-day window was between 60% and 70% CO2/ThCO2. The 10-day window criterion of OECD 301 is therefore fulfilled. The degree of DOC removal of the test substance at the end of exposure was between 90% and 100%. All validity criteria of the guideline were fulfilled.

Description of key information

Tributylamine is readily biodegradable fulfilling the 10 -day window requirement.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

-Tri-n-butylamine (TBA) was tested for ready biodegradability in two studies according to OECD 301B (modified Sturm test; BASF, 2014; OXEA, 2010):

 

In the OECD 301B key study conducted by BASF (2014) activated sludge from a wwtp was used as inoculum. The test concentration was 10 mg/L TOC (nominal). Based on TOC measurements, TBA was found to be stable for 28 days in the test solution without inoculum (abiotic control) (no significant loss, nearly 100%). The degree of biodegradation of the test substance at the end of the ten-day window reached 60-70% CO2/ThCO2.The degree of biodegradation at the end the test was 80-90% CO2/ThCO2.

 

In the supporting OECD 301B study by OXEA (2010) activated sludge from a wwtp, receiving mostly domestic sewage, was used as inoculum as well. The test concentration of TBA was 20 mg/L organic carbon (nominal). Degradation in the two replicates at the end of the 10 -day window reached 43% and 71%, respectively. The mean degradation at the end of the test was 80%.

(NOTE: Due to a deviation during the degradation phase within replicates, degradation lay marginally below the pass level (57% instead of 60%). This might be due to dissolved carbon dioxide in the test flasks. At the end of the test this dissolved carbon dioxide is driven off by addition of HCl, leading to an improved correlation between the replicates. At the end of the test, the difference between the replicates was only 6.4%.)

 

Based on a Zahn-Wellens test (OECD 302B) using industrial activated sludge as inoculum, TBA was assessed to be easily eliminated from water (97% DOC removal after 11 d; BASF AG, 1986).

In summary, tri-n-butylamine is considered to be readily biodegradable according to OECD criteria.