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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:
27 February 2012 to 04 May 2012
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
The study was conducted in accordance with international guidelines and in accordance with GLP. All relevant validity criteria were met.
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EPA OPPTS 835.3110 (Ready Biodegradability)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
Fresh activated sludge from a biological waste water treatment plant treating predominantly domestic sewage (Bois-de-Bay, Satigny, Switzerland) was used. The sludge is collected in the morning, washed three times in the mineral medium (by centrigugation at 1000 g for 10 minutes, discarding the supernatant and resuspending in mineral medium) and kept aerobic until being used on the same day.
The dry weight of suspended solids was determined by taking two 50 mL samples of the homogenised sludge, evaporating water on a steam bath, drying in an oven at 105 - 110 °C for two hours and weighing the residue.
Dry weight of suspended solids: 6.36 g/L, diluted to 1.53 g/L.
To obtain a concentration of 30 mg/L (dry weight) in 103 mL total volume. 2 mL of sludge was added (inoculum).
To obtain a concentration of 30 mg/L (dry weight) in 255 mL total volume, 5 mL of sludge was added (inoculum).
Initial conc.:
30 mg/L
Based on:
ThOD
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: According to OECD 301 Guideline
- Additional substrate: Not applicable
- Solubilising agent (type and concentration if used): Not applicable
- Test temperature: 21.8 - 22.9 °C
- pH: 7.4 - 8.0
- pH adjusted: no
- CEC (meq/100 g): Not applicable
- Aeration of dilution water: Yes
- Suspended solids concentration: 30 mg/L
- Continuous darkness: Yes
- Other:

TEST SYSTEM
- Culturing apparatus: Closed flask
- Number of culture flasks/concentration: Control x 2, Reference x 2, Test x 2
- Method used to create aerobic conditions: aeration
- Method used to create anaerobic conditions: Not applicable
- Measuring equipment: Oxitop system
- Test performed in closed vessels due to significant volatility of test substance: Yes
- Test performed in open system: No
- Details of trap for CO2 and volatile organics if used: Not applicable
- Other:

SAMPLING
- Sampling frequency: Daily
- Sampling method: In-situ oxitop measurement
- Sterility check if applicable: Not applicable
- Sample storage before analysis: No
- Other:

CONTROL AND BLANK SYSTEM
- Inoculum blank: Yes
- Abiotic sterile control: No
- Toxicity control: No
- Other:

STATISTICAL METHODS:
Not applicable
Reference substance:
benzoic acid, sodium salt
Remarks:
(Fluka, Buchs, Switzerland, Art. No. 71300), purity = 99 %
Preliminary study:
Not applicable
Parameter:
% degradation (O2 consumption)
Value:
5
Sampling time:
1 d
Parameter:
% degradation (O2 consumption)
Value:
16
Sampling time:
2 d
Parameter:
% degradation (O2 consumption)
Value:
44
Sampling time:
7 d
Parameter:
% degradation (O2 consumption)
Value:
58
Sampling time:
12 d
Parameter:
% degradation (O2 consumption)
Value:
74
Sampling time:
21 d
Key result
Parameter:
% degradation (O2 consumption)
Value:
77
Sampling time:
28 d
Parameter:
% degradation (O2 consumption)
Value:
80
Sampling time:
36 d
Details on results:
Oxygen uptakes, as read on the Oxitop controller, are corrected to account for the small differences between actual and nominal concentrations of test and reference substances.

The substance undergoes 77 % biodegradation after 28 days (80 % after 36 days) under the test conditions. The 10-day window criterion is not fulfilled (16 % biodegradation on day 2 and 58 % on day 12). The substance did not inhibit the intrinsic respiration of the inoculum the the test concentration and was therefore considered to be non-toxic to the inculum at the test concentration.

The repeatability validity criterion (not more than 20 % difference between replicates) is fulfilled for the flasks containing test substance, confirming validity of the study.
Results with reference substance:
Degradation of the reference substance exceeded 40 % after 7-days and 65 % after 14 days, meeting the relevant validity criterion.

Theoretical Oxygen Demand

Formula: C11H22N0O1

Molecular Weight: 170.3 g/mol

Theoretical Oxygen Demand (ThOD): 3.01 mg O2/mg

Biodegradation of the Test Item

 

Days:

1

2

7

12

21

28

36

O2 Uptake of Sludge (Inoculum Blank)

1a

B1

8.1

16.2

28.3

35.0

41.7

47.1

51.2

2a

B2

8.1

16.2

28.3

35.0

41.7

45.8

48.5

Mean

B

8.1

16.2

28.3

35.0

41.7

46.5

49.9

O2 Uptake of Test Substance + Sludge

19a

C1

13.5

31.1

68.9

87.7

110.3

118.3

123.3

20a

C2

12.1

31.0

67.4

87.6

106.2

114.2

120.2

O2 Uptake of Test Substance

 

C1-B

5.4

14.9

40.6

52.7

68.6

71.8

73.4

 

C2-B

4.0

14.8

39.1

52.6

64.5

67.7

70.3

% Biodegradation of Test Substance

 

D1

6

16

45

58

76

80

81

 

D2

4

16

43

58

71

75

78

mean

D

5

16

44

58

74

77

80

Calculations:

B1, B2, C1, C2, A1, A2, E1: Experimental O2 uptake values

B = (B1 + B2) / 2

D1 = 100 * (C1 - B) / ThOD * [S]

D2 = 100 * (C2 - B) / ThOD * [S] D = (D1 + D2) / 2

[S]: Initial test substance concentration (mg/L)

Biodegradation of the Reference Item

 

Days:

5

7

14

21

28

O2 Uptake of Sludge (Inoculum Blank)

1a

B1

24.2

28.3

37.7

41.7

47.1

2a

B2

24.2

28.3

36.3

41.7

45.8

Mean

B

24.2

28.3

37.0

41.7

46.5

O2 Uptake of Test Substance + Sludge

17a

A1

146.2

162.3

188.5

198.5

204.5

18a

A2

146.2

162.3

183.4

198.5

204.5

O2 Uptake of Test Substance

 

A1-B

122.0

134.0

151.5

156.8

158.1

 

A2-B

122.0

134.0

146.4

156.8

158.1

% Biodegradation of Test Substance

 

D1

73

80

91

94

95

 

D2

73

80

88

94

95

mean

D

73

80

89

94

95

Calculations:

B1, B2, C1, C2, A1, A2, E1: Experimental O2 uptake values

B = (B1 + B2) / 2

D1 = 100 * (C1 - B) / ThOD * [S]

D2 = 100 * (C2 - B) / ThOD * [S] D = (D1 + D2) / 2

[S]: Initial test substance concentration (mg/L)

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable, but failing 10-day window
Conclusions:
The substance undergoes 77 % biodegradation after 28 days (80 % after 36 days) under the test conditions. The 10-day window criterion is not fulfilled (16 % biodegradation on day 2 and 58 % on day 12). The test item can not be considered as readily biodegradable, however the results indicate that the substance may be regarded as inherently and ultimately biodegradable.
Executive summary:

The ready biodegradability of the test item was determined in accordance with OECD 301F (Manometric Respirometry Test). The substance underwent 77 % biodegradation after 28 -days (80 % after 36 days) under test conditions. The 10 -day window criterion was not fulfilled (16 % biodegradation on day 2 and 58 % on day 12). The test item did not inhibit the intrinsic respiration of the inoculum at the test concentration and was therefore considered to be non-toxic to the inoculum at the test concentration.

The test item should be regarded as not readily biodegradable according to the study. However, based on the results the test item may be regarded as inherently and ultimately biodegradable.

Description of key information

28d Biodegradation: 77 %, readily biodegradable but failing the 10-day window; OECD 301F; Anon, 2012

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable but failing 10-day window

Additional information

In a single key study, the ready biodegradability of the test item was determined in accordance with OECD 301F (Manometric Respirometry Test). The substance underwent 77 % biodegradation after 28 -days (80 % after 36 days) under test conditions. The 10 -day window criterion was not fulfilled (16 % biodegradation on day 2 and 58 % on day 12). The test item did not inhibit the intrinsic respiration of the inoculum at the test concentration and was therefore considered to be non-toxic to the inoculum at the test concentration.

The test item should be regarded as not readily biodegradable according to the study. However, based on the results the test item may be regarded as inherently and ultimately biodegradable.

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