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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:
2003-03-28 to 2003-06-24
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)
Version / remarks:
December 1992
Deviations:
no
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Version / remarks:
adopted July 17, 1992
Deviations:
no
GLP compliance:
yes (incl. certificate)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Municipal sewage treatment plant: ’Waterschap de Maaskant’, ’s-Hertogenbosch, the Netherlands.
- Storage conditions: continuous aeration until further treatment
- Storage length: not specified
- Preparation of inoculum for exposure: The sludge was allowed to settle (30-90 minutes) and the liquid decanted for use as inoculum at the amount of 10 mL/L of mineral medium.
- Concentration of sludge: 3.7 g/L
- Water filtered: yes
- Type and size of filter used, if any: Passed over activated carbon and ion-exchange cartridges (Milli-O) (Millipore Corp., Bedford, Mass., USA).
Duration of test (contact time):
28 d
Initial conc.:
19 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Composition of medium: A) 8.50 g KH2PO4, 21.75 g K2HPO4, 67.20 g Na2HPO4 x 12 H2O, 0.50 g NH4Cl dissolved in 1L Milli-Q water, pH 7.4 ± 0.2 B) 22.50 g MgSO4 x 7 H2O dissolved in 1 L Milli-Q water. C) 36.40 g CaCl2 x 2H2O dissolved in 1L Milli-Q water. D) 0.25 g FeCl3 x 6 H2O dissolved in 1L Milli-Q water. Mineral Medium 1L mineral medium contains: 10 mL solution A), 1 mL solution B to D and Milli-RO water.
- Test temperature: between 21.4 and 23.5°C
- pH: 7.4 to 7.8
- pH adjusted: no
- Aeration of dilution water: Preincubation medium was aerated with CO2-free air overnight
- Suspended solids concentration: 3.7g/L

TEST SYSTEM
- Number of culture flasks/concentration: 6 bottles for test suspension (2) inoculum blank (2) positive control (1) toxicity control (1)
- Measuring equipment: Titration of Ba (OH)2, which was formed by CO2 production,with 0.05 M standardized HCl.
- Details of trap for CO2 and volatile organics if used: Reaction of barium hydroxide with CO2 producing precipitating barium carbonate.


SAMPLING
- Sampling frequency: Titrations were made every second or third day during the first 10 days, and thereafter at least every fifth day until the 28th day.
- Sampling method: Each time the Co2-absorber nearest to the test bottle was removed for titration; each of the remaining two absorbers wasmoved one position in the direction of the test bottle. A new CO2 absorber was placed at the far end of the series.


CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Toxicity control: yes, 40 mg/L sodium acetate solution
Reference substance:
acetic acid, sodium salt
Key result
Parameter:
% degradation (CO2 evolution)
Remarks:
Mean value of two test bottles
Value:
8
Sampling time:
9 d
Key result
Parameter:
% degradation (CO2 evolution)
Remarks:
Mean value of two test bottles
Value:
8
Sampling time:
14 d
Key result
Parameter:
% degradation (CO2 evolution)
Remarks:
Mean value of two test bottles
Value:
17
Sampling time:
29 d

Table 1: C02 production and percentage biodegradation of the test substance (bottle A).

Day

HCI (0.05 N) titrated (ml)

Produced C02 (ml HCI)

Produced C02 (mg)

Cumulative C02 (mg)

Degradation

Blank (mean)

bottle A

2

5

7

9

14

19

23

27

29

29

29

43.58

47.09

45.46

45.17

44.82

45.60

47.81

46.01

44.88

47.31

48.99

40.28

43.81

45.90

46.21

45.27

44.32

46.78

45.24

44.13

47.05

47.98

3.30

3.28

0.00

0.00

0.00

1.28

1.03

0.77

0.75

0.26

1.01

3.6

3.6

0.0

0.0

0.0

1.4

1.1

0.8

0.8

0.3

1.1

3.6

7.2

7.2

7.2

7.2

8.6

9.8

10.6

11.4

11.7

12.8

4

8

8

8

8

10

11

12

13

13

14

Table 2: C02 production and percentage biodegradation of the test substance (bottle B).

Day

HCI (0.05 N) titrated (ml)

Produced C02 (ml HCI)

Produced C02 (mg)

Cumulative C02 (mg)

Degradation

Blank (mean)

bottle B

2

5

7

9

14

19

23

27

29

29

29

43.58

47.09

45.46

45.17

44.82

45.60

47.81

46.01

44.88

47.31

48.99

40.85

43.80

45.30

45.48

45.13

43.95

45.05

43.60

43.54

47.31

47.61

2.73

3.29

0.16

0.00

0.00

1.65

2.76

2.41

1.34

0.00

1.38

3.0

3.6

0.2

0.0

0.0

1.8

3.0

2.7

1.5

0.0

1.5

3.0

6.6

6.8

6.8

6.8

8.6

11.6

14.3

15.8

15.8

17.3

3

7

8

8 8

10

13

16

18

18

20

Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
In the present study conducted according to OECD guideline 301B, activated sludge from a municipal sewage treatment plant was incubated with 38.5 and 37.8 mg/2L bottle of the test substance for 28 days. Since measurements revealed a degradation of 14 and 20% during the whole test period the substance is considered to be not readily biodegradable.

Description of key information

- OECD guideline 301B study,GLP, activated sludge incubated with 38.5 and 37.8 mg/2L bottle of the test substance for 28 days, degradation of 14 and 20% during the whole test period

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

In the present study conducted according to OECD guideline 301B, activated sludge from a municipal sewage treatment plant was incubated with 38.5 and 37.8 mg/2L bottle of the test substance for 28 days. Since measurements revealed a degradation of 14 and 20% during the whole test period the substance is considered to be not readily biodegradable.