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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:
19 December 1996 – 17 January 1997
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
The study meets OECD Guideline No 301F requirements.
Reason / purpose for cross-reference:
reference to same study
Reason / purpose for cross-reference:
reference to other study
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
no
Principles of method if other than guideline:
not applicable
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
Source of activated sludge: biological waste water treatment plant treating predominantly domestic sewage (City of Geneva, Aire)

Preconditioning: the sludge is collected in the morning, washed three times in the mineral medium (by centrifuging at 1000 g for 10 min, discarding the supernatant and resuspending in mineral medium) and kept aerobic until being used on the same day.

Dry weight of suspended solids: 3.793 g/L

Concentration of sludge: 30 mg dw/L
Duration of test (contact time):
28 d
Initial conc.:
100 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: the following stock solutions were prepared
Solution A: KH2PO4: 8.5 g/L, K2HPO4: 21.75 g/L, Na2HPO4.2H2O: 33.4 g/L, NH4Cl: 0.5 g/L
Solution B: CaCl2: 27.5 g/L
Solution C: MgSO4.7H2O: 22.5 g/L
Solution D: FeCl3.6H2O: 0.25 g/L, HCl conc.: one drop
Mineral medium was prepared by mixing 50 mL of solution A and 2000 mL of deionized water, adding 5 mL of each of the solutions B, C and D and making up to 5 L with deionized water.
- Source/preparation of dilution water: deionized water containing less than 10 mg/L dissolved organic carbon
- Test temperature: 22 °C

TEST SYSTEM
- Culturing apparatus: flasks of the volumetric respirometer (SAPROMAT)
- Number of culture flasks/concentration: two
- Details of trap for CO2 if used: evolved CO2 was absorbed by sodalime pellets

MEASURING EQUIPMENTS:
- Respirometer: SAPROMAT D 12 (J. M. VOITH GmbH, Heidenheim, Germany)

SAMPLING
- Sampling frequency: everyday the oxygen consumption of each flask was recorded and correct temperature and stirring were checked. At the end of the test period (normally 28 days), the pH of each flask was measured again.

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes; containing inoculum only
- Procedure control: yes; containing reference substance (aniline) with inoculated medium
- Toxicity control: yes; containing test material and reference substance (sodium benzoate) with inoculated medium
Reference substance:
benzoic acid, sodium salt
Remarks:
100 mg/L; purity: min. 99.0 %; source: Fluka, Switzerland
Preliminary study:
no data
Test performance:
no data
Key result
Parameter:
% degradation (O2 consumption)
Value:
78
Sampling time:
28 d
Details on results:
Initial test material concentration: 100 mg/L

Theoretical oxygen demand (ThOD) = 2.61 mg O2/mg

% biodegradation on Day 7: > 10 %

% biodegradation on Days 17 > 60 %

% biodegradation on Days 28 = 78 %
Results with reference substance:
Theoretical oxygen demand (ThOD) = 1.67 mg O2/mg

% biodegradation on Day 5: > 60 %

% biodegradation on Days 14 = 83 %

Table 5.2.1/2: Test material: Biological Oxygen Demand (BOD, mg O2/L, adjusted to nominal concentrations)

 

Days

5

7

14

17

21

28

BOD Sludge

1st flask

B1

22.0

23.0

31.0

32.0

37.0

42.0

2nd flask

B2

22.0

23.0

30.0

31.0

37.0

44.0

mean

B

22.0

23.0

30.5

31.5

37.0

43.0

BOD Test substance

1st flask

C1

39.3

42.1

176.2

207.6

240.9

245.6

2nd flask

C2

39.4

77.6

177.1

217.3

242.2

248.9

1st flask corrected

C1-B

17.3

19.1

145.7

176.1

203.9

202.6

2nd flask corrected

C2-B

17.4

54.6

146.6

185.8

205.2

205.9

% Degradation

1st flask

D1

7

7

56

67

78

78

2nd flask

D2

7

21

56

71

79

79

mean

D

7

14

56

69

78

78

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)

 

 

Table 5.2.1/3: Reference substance (sodium benzoate): Biological Oxygen Demand (BOD, mg O2/L, adjusted to nominal concentrations)

 

Days

5

7

10

14

21

28

BOD Sludge

1st flask

B1

22

23

26

31

37

42

2nd flask

B2

22

23

24

30

37

44

mean

B

22

23

25

30.5

37

43

BOD reference substance

1st flask

A1

143

152.9

164.9

172.9

184.9

195.9

2nd flask

A2

136

145

154.9

163.9

171.9

178.9

1st flask corrected

A1-B

121

129.9

139.9

142.4

147.9

152.9

2nd flask corrected

A2-B

114

122

129.9

133.4

134.9

135.9

% Degradation

1st flask

D1

73

78

84

86

89

92

2nd flask

D2

68

73

78

80

81

82

mean

D

71

76

81

83

85

87

B = (B1 + B2)/2;

D1 = 100*(A1 - B)/ThOD*[S]; D2 = 100*(A2 - B)/ThOD*[S]; D = (D1 + D2)/2

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

Validity criteria fulfilled:
yes
Remarks:
% degradation in reference material reached the pass levels by Day 14; oxygen uptake of inoculum blank was < 60 mg O2/L; pH of the test solutions at the end of the test was 7.40-7.44; toxicity control showed no toxicity to microorganisms
Interpretation of results:
readily biodegradable
Conclusions:
Nopyl acetate was readily biodegradable in a test carried out according to OECD Guideline No 301 F.
Executive summary:

In a ready biodegradation study performed according to OECD Guideline No 301 F and GLP, nopyl acetate was tested at a concentration of 100 mg/L and the inoculum was activated sewage sludge, domestic. The degradation of the test material was assessed by the determination of the oxygen consumption. The test treatments, inoculum blank, procedure control and toxicity control were measured in duplicates.


 


At 100 mg/L test concentration, greater than 10 % degradation was reached on Day 7 and greater than 60 % biodegradation was reached on Day 17. The pass level for ready biodegradability was reached in the required 10-d window within the 28-d period of the test: 78% degradation on Day 28.


 


The reference material (sodium benzoate) reached greater than 60 % biodegradation within 5 days. The biodegradation curves obtained with the reference substance alone and with test material+reference substance show no toxic effect on the micro-organisms. Hence, it met the validity criteria for reference material and toxicity control.


 


Therefore, nopyl acetate was readily biodegradable.

Description of key information

Screening for ready biodegradability was performed by a manometric respiratory test.
Nopyl acetate is readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Key study conducted according to OECD 301 F Guideline and GLP without deviation.

Nopyl acetate was tested at a concentration of 100 mg/L. The inoculum derived from domestic sewage sludge. Degradation was assessed by measurement of oxygen consumption.

The pass level for ready biodegradability was reached in the required 10-d window within the 28-d period of the test: 78% degradation on Day 28. This result can be used as key value for chemical safety assessment.