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Environmental fate & pathways

Biodegradation in water: screening tests

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Administrative data

Endpoint:
biodegradation in water: inherent biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1995
Report Date:
1995

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 302 B (Inherent biodegradability: Zahn-Wellens/EMPA Test)
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
liquid
Details on test material:
30% w/w aqueous solution of Cyclohexylhydroxydiazene 1-oxide, potassium salt
Specific details on test material used for the study:
Name of the test substance: K-HDO, techn. 30%
Chemical Name: N-Cyclohexyldiazeniumdioxy-potassium
Molecular formula: C6H13N2O3K
Molecular weight (g/mol): 200.28 (pure substance)
Batch No.: 74 N 9702
Manufacturing date: 07.02.95
Odour: product specific
Colour: Colourless
State of aggregation: liquid
Density (g/cm³ at 20 °C): 1.13
Solubility in water (mg/L): miscible in each ratio
Instability: Acids
Remarks for storage: store at room temperature and in darkness
Homogeneity: yes, aqueous solution
Purity of test substance: technical grade, 30 % active ingredient content
pH: 10.5 (of the 30% aqueous solution)

Study design

Inoculum or test system:
activated sludge (adaptation not specified)
Details on inoculum:
- Source of inoculum/activated sludge: Activated sludge from laboratory plants running with municipal and synthetic waste water
- Concentration of sludge: 1g/L dry matter content
Duration of test (contact time):
28 d
Initial test substance concentration
Initial conc.:
2 mg/L
Based on:
act. ingr.
Details on study design:
Test Procedure
The static Zahn-Wellens test is a static method to determine the ultimate, potential aerobic biodegradation of a test substance (inherent biodegradability) and the elimination from water, respectively. The test substance, a defined inorganic medium and as inoculum activated sludge from a municipal sewage plant or laboratory plant were mixed and aerated at room temperature up to 28 days. Samples are taken in regular intervals and were analysed in this case with substance specific analysis. In addition to the samples with test substance, an assay to determine the blank value (no test substance) and a test with a reference substance was performed.
Reference substance
Reference substance:
diethylene glycol

Results and discussion

% Degradationopen allclose all
Key result
Parameter:
% degradation (DOC removal)
Value:
>= 98
Sampling time:
28 d
Key result
Parameter:
% degradation (DOC removal)
Value:
57
Sampling time:
3 h
Details on results:
Decrease of the test substance (substance specific analysis) after 28 days: 98 %
Decrease of the test substance (substance specific analysis) after 3 hours: 57 %
The test substance is well eliminated from water
See also tables below

BOD5 / COD results

Results with reference substance:
see tables below

Any other information on results incl. tables

Modified static Zahn-Wellens Test

 

Overview of the measured values

Test substance: K-HDO, techn. 30%; reference substance: diethylene glycol

 

Analysis: BW1, KS1: DOC after centrifugation

PS1: substance specific analysis after centrifugation

 

Measured values: BW1, KS1: [mg/L DOC], PS1: [mg/L K-HDO] and pH values of the test measurements

 

Date

Day

BW1

a b pH

KS1

a b pH

PS1

pH

26.6.95

0

0.0

0.0

7.0

226

223

6.9

2

7.1

26.6.95

0.125

3.6

3.5

7.8

208

206

7.9

0.8

7.8

27.6.95

1

4.4

4.1

7.2

204

204

7.2

0.9

7.3

30.6.95

4

7.8

7.5

7.0

190

188

5.3

0.6

7.2

3.7.95

7

8.6

9.3

6.7

15.3

15.5

8.1

0.4

6.8

5.7.95

9

6.6

6.6

6.9

9.6

9.6

7.2

nv

nv

6.7.95

10

6.4

7.8

7.1

7.6

8.4

7.1

0.4

7.2

10.7.95

14

7.7

7.9

7.0

8.0

7.9

7.1

0.4

7.0

13.7.95

17

 

 

 

 

 

 

0.2

6.8

17.7.95

21

 

 

 

 

 

 

0.04

6.8

20.7.95

24

 

 

 

 

 

 

0.02

6.9

23.7.95

27

 

 

 

 

 

 

0.02

7.0

24.7.95

28

 

 

 

 

 

 

0.04

7.1

 

remarks: a/b = DOC single measurements

nv = this value is not determined because no sampling point occurred

DOC-measurements below the detection limit of 0.1 mg/L are presented in the table as 0 mg/L

The substance specific analysis of sample 95/0179/10/2BW1/6/00/00 yielded about 0.03 mg/l K-HDO. The tabulated PS1-values consider this result already.

The KS1 value (reference substance) was accidentally tested again at day 14 although this test was just finished at day 10.The result validates the previous values.

Degree of elimination D”(T) [%] KS1 (DOC-Analysis), PS1 (substance specific analysis)

Date

Day

KS1 202 mg/L DOC*

PS1 2 mg/L K-HDO (active substance)

26.6.95

0

0

0

26.6.95

0.125

-1

57

27.6.95

1

1

51

30.6.95

4

10

68

3.7.95

7

97

79

5.7.95

9

99

-

6.7.95

10

100

79

10.7.95

14

100

79

13.7.95

17

 

90

17.7.95

21

 

98

20.7.95

24

 

99

23.7.95

27

 

99

24.7.95

28

 

98

 

Remarks: * = measured adjusted start concentration CA”

The degree of elimination D”(T) relates to the measured, adjusted start concentration CA”.

                           

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Conclusions:
The elimination of K-HDO from water by absorption has been verified with this test; it is assumed that this will normally also take place in sewage plants and the environment.
Executive summary:

The elimination of K-HDO from water by absorption has been verified with this test; it is assumed that this will normally also take place in sewage plants and the environment.

Criteria for validity:

Reference substance: diethylene glycol

Degree of degradation of the reference substance (% DOC): 97 after 7 days

Degradation of the reference substance after 14 days > 80%: yes

Test is valid:  yes