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Environmental fate & pathways

Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: screening test, other
Remarks:
inherent biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2015-09-02 to 2015-09-30
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 302 B (Inherent biodegradability: Zahn-Wellens/EMPA Test)
Version / remarks:
(1992)
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): municipal wastewater treatment plant Breisgauer Bucht, 800 mg dry solids per litre (ratio between inoculum and test item (as TOC) is 4:1)
- Sampling date: 1 September 2015- Preparation of inoculum for exposure: activated sludge was washed twice by settling the sludge, decanting the supernatant and resuspending the sludge in aerated tap water
- Concentration of sludge: 3.6 g/L dry solid after 3 h drying at 105°C (mean of triplicate measurements)
Duration of test (contact time):
28 d
Initial conc.:
10 g/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
DOC removal
Details on study design:
TEST CONDITIONS
- Composition: about 1000 mL mineral medium, 47.5 ml stock solution (corresponding 200 mg/L TOC), 355 ml pre-washed activated sludge (3.6 g d.s./l), corresponding to a final concentration of 800 mg d.s./l, and a volume of 1600 mL was filled up with a corresponding amount of mineral medium
- Test temperature: 20.8 - 21.4°C
- pH: test vessels 6.3 -7.6, blank vessels 6.7 - 7.5, reference substance vessels 6.6 - 8.0
- pH adjusted: yes (1 molar NaOH)
- Aeration of dilution water: yes- Suspended solids concentration: 3.6 g d.s./l
- Continuous darkness: diffuse light
TEST SYSTEM
- Culturing apparatus: Because of the high toxicity of the test item 2000 mL gas wash bottles connected with 250 ml gas wash bottle filled with 200 ml deionised water was used to obtain a closed system and to avoid a contamination of the environment with aerosols.
- Number of culture flasks/concentration: 2, only 1 for toxicity control
- Method used to create aerobic conditions: humified pressured air supplied by aquarium pumps connected with gas-washed bottles and 1 ml glass pipettes
- Measuring equipment: temperature: minimum/maximum-thermometer; pH: pH electrode and pH-meter 330; DOC: differential method (TC/IC) with a total Carbon analyser; CO2: non-dispersive infrared gas analyser (NDIR)
- Test performed in closed vessels: yes
SAMPLING
- Sampling frequency: 0 h, 3 h, 2 d, 7 d, 14 d, 21 d, 27 d, 28 d after start
- Sampling method: 20 ml of supernatant medium and filtered (membrane filter 0.45 µm) and washed with deionised water and filtered medium
- Sample storage before analysis: DOC measurement was performed at once or samples were deep-frozen at -18°C in falcon flasks
CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Toxicity control: yes
Reference substance:
diethylene glycol
Key result
Parameter:
% degradation (DOC removal)
Value:
>= 97 - <= 98
Sampling time:
28 d
Remarks on result:
other: DOC-elimination: 97-98% using total TOC as reference value, 98% using DOC after 3 hours as reference value
Details on results:
Due to the low degree of adsorption of the test item, the DOC-elimination can be attributed directly to biodegradation.

Table 1: DOC-measurement

 

Scopolamin

Diethylene glycol

Tox-control

Blank

 

Vessel 5

Vessel 6

Vessel 3

Vessel 4

Vessel 7

Vessel 1

Vessel 2

DOC test item [mg/L]

6731

6731

506300

506300

 

 

 

Volume of the test vessel in ml

1600

1600

1600

1600

 

 

 

Volume test item in ml/vessel

47,5

47,5

1

1

 

 

 

Calculated DOC at test start [mg/L]

200

200

316

316

516

 

 

 

 

 

 

 

 

 

 

0 d

214,3

208,3

337,8

338,4

563,5

3,1

4,9

0,125 d

233,4

209,1

336,2

337,9

559,9

5,6

5,2

2 d

210,4

211,2

333,4

335,7

566,4

5,7

5,9

7 d

28,3

30,7

197,3

122,3

347,9

7,4

6,7

14 d

13,1

10,4

8,1

8,4

22,2

7,7

7,2

21 d

11,0

11,8

8,8

9,2

12,3

7,4

5,3

27 d

11,7

13,0

8,3

9,6

15,4

7,6

7,4

28 d

12,1

13,5

9,2

9,2

15,5

6,7

7,2

 

Table 2: DOC-degradation [%] referred to 3-h value

 

Scopolamin

Diethylene glycol

 Tox-control

 

Vessel 5

Vessel 6

Vessel 3

Vessel 4

Vessel 7

0,125 d

0

0

0

0

0

2 d

10

-1

1

1

-1

7 d

91

88

42

65

39

14 d

98

99

100

100

97

21 d

98

97

99

99

99

27 d

98

97

100

99

99

28 d

98

97

99

99

98

Table 3: DOC-degradation [%] referred to initial TOC

 

Scopolamin

Diethylene glycol

Tox-control

 

Vessel 5

Vessel 6

Vessel 3

Vessel 4

Vessel 7

0 d

-15

-3

-5

-6

-8

0,125 d

-3

-3

-4

-5

-9

2 d

89

88

39

63

34

7 d

97

99

100

100

97

14 d

98

97

99

99

99

21 d

 

97

99

99

99

27 d

98

97

100

99

98

28 d

97

97

99

99

98

Elimination is referred to the calculated DOC at test start

Validity criteria fulfilled:
yes
Interpretation of results:
inherently biodegradable, fulfilling specific criteria
Conclusions:
The test item Scopolamine is inherent biodegradable according to OECD 302 B.

Description of key information

The test item is considered to be inherent biodegradable according to OECD 302 B.

Key value for chemical safety assessment

Biodegradation in water:
inherently biodegradable, fulfilling specific criteria

Additional information