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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:
26 August 2010- 24 September 2010
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Fully documented study run under GLP and according to international guidelines.
Qualifier:
according to
Guideline:
other: ISO 14593:2005 adopted 2005 “Water quality - Evaluation of ultimate aerobic biodegradability of organic compounds in aqueous medium – Method by analysis of inorganic carbon in sealed vessels (CO2 headspace test)”
Deviations:
yes
Remarks:
Uncritical deviations: The temperature was slightly lower than demanded in the study plan (18.4 – 21.6 °C). Only five points of measurement were performed instead of eight. The content of OC and IC was determined on day 5 though not required.
Qualifier:
according to
Guideline:
OECD Guideline 310 (Ready Biodegradability - CO2 in Sealed Vessels (Headspace Test)
Deviations:
yes
Remarks:
Uncritical deviations: The temperature was slightly lower than demanded in the study plan (18.4 – 21.6 °C). Only five points of measurement were performed instead of eight. The content of OC and IC was determined on day 5 though not required.
GLP compliance:
yes (incl. certificate)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
The sludge was taken from the activation basin of the ESN (Stadtentsorgung Neustadt) sewage treatment plant, Im Altenschemel, NW-Lachen-Speyerdorf.
Date of collection: 26. Aug. 2010.
The sludge was washed with tap water twice, then filtrated through a cloth and resuspended in test medium. It was then aerated. The dry matter was determined with 4000 mg suspended solids /L.
Duration of test (contact time):
28 d
Initial conc.:
26.32 mg/L
Based on:
other: nominal
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Composition of medium: according to OECD 310

TEST SYSTEM
- Number of culture flasks/concentration:
Blank: 1 flask
Control: 2 flasks
Positive control: 2 flasks
Test substance: 2 flasks
Abiotic control: 1 flask
Toxicity control:1 flask

SAMPLING
The test was performed at room temperature (18.4 – 21.6 °C) without direct lighting.
Duration of the test was 28 days. During this time, the created CO2 in the vessels was determined on days 0, 5, 13, 21, and, 28.
Sampling dates were derived from the degradation behaviour of the test item.
Reference substance:
aniline
Parameter:
% degradation (CO2 evolution)
Value:
4.3
Sampling time:
0 d
Remarks on result:
other: Based on 2 replicates
Parameter:
% degradation (CO2 evolution)
Value:
3.6
Sampling time:
5 d
Remarks on result:
other: Based on 2 replicates
Parameter:
% degradation (CO2 evolution)
Value:
10.7
Sampling time:
13 d
Remarks on result:
other: Based on 2 replicates
Parameter:
% degradation (CO2 evolution)
Value:
3.6
Sampling time:
21 d
Remarks on result:
other: Based on 2 replicates
Parameter:
% degradation (CO2 evolution)
Value:
14.1
Sampling time:
28 d
Remarks on result:
other: Based on 2 replicates
Results with reference substance:
Degradation of the positive control was 69% after thirteen days.

For verification of bioavailability of the volatile test item, the content of organic carbon and inorganic carbon in all vessels was determined at the end of the test and on day 5. They were measured at least 3 times.

IC-values in ppm

Day

Blank

Control 1

Control 2

Pos. Control 1

Pos. Control 2

Test 1

Test 2

Abiotic Control

Toxicity Control

0

7.20

7.29

6.09

7.10

8.20

5.32

9.77

6.22

5.42

5

1.63

1.67

2.24

2.73

3.38

2.53

2.83

2.20

13.34

13

4.09

4.28

2.60

18.38

16.18

5.55

5.62

3.70

20.77

21

3.23

4.29

4.39

18.21

19.23

5.48

4.62

3.47

21.18

28

1.75

3.09

2.35

20.02

18.67

5.31

5.44

2.99

19.72

28

2.73

2.48

3.53

20.16

18.63

6.33

6.10

3.13

23.40

28

2.07

2.99

3.41

18.84

19.04

6.14

5.40

2.90

19.80

 

DOC-values in ppm
Day
Blank
Control 1
Control 2
Pos. Control 1
Pos. Control 2
Test 1
Test 2
Abiotic Control
Toxicity Control
5
2.15
1.54
1.02
17.95
17.2
14.58
14.72
14.5
14.9
28
0
0
0
0
0
10.76
10.99
12.48
0
28
0
0
0
0
0
9.07
8.21
12.95
6.69
28
0
0
0
0
0
9.44
10.37
11.84
0

For verification of bioavailability of the volatile test item, the content of organic carbon and inorganic carbon in all vessels was determined on day 5 and at the end of the test. A well detectable content of organic carbon was found in. all test vessels, abiotic control vessels and in one toxicity control vessel on day 5 and at the end of the test. That means that equilibrium between solution and head space was present during the test and bioavailability of the test item was given.

 

Net Inorganic Carbon

The net inorganic carbon was calculated from the measured IC values by subtraction of the blank (medium only without inoculum).

The net IC values are presented in the following table:

Table 1     Net IC-values in ppm

Day

Control 1

Control 2

Pos. Control 1

Pos. Control 2

Test 1

Test 2

Abiotic Control

Toxicity Control

0

0.09

-1.11

-0.10

1.00

-1.88

2.57

-0.98

-1.78

5

0.04

0.61

1.10

1.75

0.90

1.20

0.57

11.71

13

0.19

-1.49

14.29

12.09

1.46

1.53

-0.39

16.68

21

1.06

1.16

14.98

16.00

2.25

1.39

0.24

17.95

28

0.91

0.17

17.84

16.49

3.13

3.26

0.81

17.54

28

0.30

1.35

17.98

16.45

4.15

3.92

0.95

21.22

28

0.81

1.23

16.66

16.86

3.96

3.22

0.72

17.62

 

Negative values are attributed to measurement uncertainties and variation within the test flasks. In these low concentrations, this is considered as typical.

Table 2     Degradation values in %

Day

Pos. Control 1

Pos. Control 2

Pos. Control Mean

Test 1

Test 2

Test Mean

Abiotic Control

Toxicity Control

0

2.0

7.5

4.8

-6.9

15.4

4.3

-4.9

-3.2

5

3.9

7.1

5.5

2.9

4.4

3.6

2.9

28.7

13

74.6

63.6

69.1

10.6

10.9

10.7

-2.0

43.6

21

69.2

74.3

71.8

5.7

1.4

3.6

1.2

42.4

28

83.4

78.9

81.1

14.8

13.4

14.1

4.1

45.3

 Biological Results

The results are presented in the following table.

Table 3     Results

Parameter

Value

Lag phase

not detected

10-day-window

not detected

Degradation at the end of 10-day-window

not detected

Degradation at the end of the test

14 %

 

Validity criteria fulfilled:
yes
Remarks:
Degradation of positive control > 60% at day 14; Mean IC content of controls at the end of the test < 3 mg/L
Interpretation of results:
other: not readily biodegradable
Conclusions:
During the whole test an equilibrium between solution and head space was present and bioavailability of the test item was given. A degradation of the test item of 14% only was observed after 28 days. Therefore, the test item 2-propanol and 2-butanol production, distn. residues consisting mainly of di-isobutylether, di-isopropylether, C3- and C4-alcohols and C6-hydrocarbons is not readily biodegradable following ISO 14593:2005.
Executive summary:

The test item was tested for ready biodegradability using a concentration of 26.32 mg 2-propanol and 2-butanol production, distn. residues /L (consisting mainly of di-isobutylether, di-isopropylether, C3- and C4-alcohols and C6-hydrocarbons) in test medium following ISO 14593:2005. Aniline was chosen as positive control.

Activated sludge from a sewage treating plant was used as inoculum (concentration 4 mg suspended solids/L) and the test was left running for 28 days.

All validity criteria were met and the test item concentration remained stable over the whole test. Degradation of the positive control was 69% after thirteen days.

The following data were determined for the test item:

- 10-day-window: not detectable

- degradation at the end of 10-day-window: none

- degradation at the end of the test: 14 %

Therefore, regardless of the 10-day-window, the test item 2-propanol and 2-butanol production, distn. residues is not readily biodegradable following ISO14593:2005.

Description of key information

No degradation of the test item was observed after 28 days. The test item “2-propanol and 2-butanol production, distn. residues” (consisting mainly of di-isobutyl ether, di-isopropyl ether, C3- and C4-alcohols and C6-hydrocarbons) is not readily biodegradable following ISO 14593:2005.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

The ready biodegradation of "2-propanol and 2-butanol production, distn. residues" (consisting mainly of di-isobutyl ether, di-isopropyl ether, C3- and C4-alcohols and C6-hydrocarbons) was tested according to ISO 14593:2005 under GLP. No significant degradation (14%) of the test item was observed after 28 days. As a result, "2-propanol and 2-butanol production, distn. residue" is not considered readily biodegradable.