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Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
From 02 Feb. 2009 to 04 Mar. 2009
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
This study was performed according to OECD Guideline 301F, EU Method C.4-D and GLP statement. All validity criteria were fulfilled and no deviations were observed. This study is considered reliable without restriction.
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Version / remarks:
1992
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)
Version / remarks:
1992
Deviations:
no
Principles of method if other than guideline:
Not applicable
GLP compliance:
yes (incl. certificate)
Remarks:
2008-11-12
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): ARA Ergolz II, Füllinsdorf, Switzerland

The sludge was washed twice with tap water by centrifugation and the supernatant liquid phase was decanted. A homogenized aliquot of the final sludge suspension was weighted, thereafter dried and the ratio of wet to dry weight was calculated. Based on this ratio, calculated amounts of wet sludge were suspended in test water to obtain a concentration equivalent to 4 g (+/- 10%) dry material per liter. During the holding period of two days prior to use, the sludge was aerated at room temperature. Prior to use, the sludge was first thoroughly mixed and then diluted with test water to a concentration of 1 g per liter (dry weight basis). Based on the determined dry weight of this dluted activated sludge defined amounts were added to test water to obtain a final concentration of 30 mg dry material/L.
Duration of test (contact time):
28 d
Initial conc.:
100 mg/L
Based on:
test mat.
Initial conc.:
234 mg/L
Based on:
ThOD/L
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: The test water was prepared according to the testing guidelines.
- Test temperature: 22°C, maintained with a built-in thermostat and checked once per week.
- pH: Prior to test start, the pH was measured in each test flask before the addition of the activated sludge inoculum (= 7.3-7.4). At the end of the incubation, the pH was measured again in each test flask (= 7.3-8.0).
- pH adjusted: yes.
- Aeration of dilution water: no data
- Suspended solids concentration: 30 mg dry material /L
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 500 mL reaction vessels
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: no data
- Method used to create anaerobic conditions: not applicable
- Measuring equipment: SAPROMAT D12 (Voith GmbH, Heidenheim, Germany)
- Other: The biodegradation process consumes the dissolved oxygen in the test medium and generates CO2. The CO2 is adsorbed by soda lime, which results in a decrease of the total pressure in the airtight test flasks. The pressure drop is detected and converted into an electrical signal by means of an electrode type manometer. The consumed oxygen is replaced by electrolytically generated oxygen from a copper sulfate solution.

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes, 2
- Abiotic sterile control: no
- Toxicity control: yes, 1
- Other: Procedure control yes, 2
See table 5.2.1/1 in "Any other information on materials and methods incl. tables".
Reference substance:
benzoic acid, sodium salt
Preliminary study:
Not applicable
Test performance:
This study is valid.
Key result
Parameter:
% degradation (O2 consumption)
Value:
-1
Sampling time:
28 d
Remarks on result:
other: mean of two replicates. Negative value due to higher oxygen consumption in the inoculum controls than in the test flasks with test item.
Details on results:
See tables 5.2.1/2 and 5.2.1/3 in "Any other information on results incl. tables".

In the toxicity control, the course of biodegradation over the 28 day exposure period was similar to the two procedure controls, containing only the reference item. Within 14 days of exposure, biodegradation amounted to 36%. Thus according to the test guidelines, the test item had no inhibitory effect on activated sludge microorganisms at the tested concentration of 100 mg/L because biodegradation in the toxicity control was > 25% within 14 days.
Results with reference substance:
In the procedure controls, the reference item was degraded by an average of 87% by exposure day 14, thus confirming suitability of the activated sludge. At the end of the test (day 28), the reference item was degraded by an average of 93%.

Table 5.2.1/2: Oxygen consumption in the test flasks

Time (days)

Cumulative oxygen consumption (mg/L)

Test item

Inoculum control

Procedure control

Toxicity control

Replicate no.

Replicate no.

Replicate no.

Replicate no.

1

2

1

2

1

2

1

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

0

7

9

-

-

12

13

14

14

15

-

-

16

16

17

17

18

-

-

18

19

19

19

19

-

-

19

19

19

0

4

4

-

-

7

8

8

9

9

-

-

11

11

12

12

12

-

-

13

14

14

15

15

-

-

15

15

15

0

2

4

-

-

7

8

9

10

11

-

-

12

12

12

13

13

-

-

14

15

15

15

16

-

-

17

17

17

0

0

7

-

-

12

13

14

15

16

-

-

17

18

19

19

20

-

-

21

22

22

23

23

-

-

23

23

23

0

19

93

-

-

131

138

143

146

149

-

-

157

160

162

164

167

-

-

171

172

173

174

174

-

-

176

177

177

0

19

92

-

-

124

133

139

143

146

-

-

153

156

159

161

164

-

-

169

170

171

172

172

-

-

173

174

174

0

19

96

-

-

120

125

132

138

142

-

-

152

156

159

162

165

-

-

169

172

173

174

175

-

-

176

176

176

Table 5.2.1/3: Biodegradation in the test flasks

Time (days)

Percentage biodegradation*

Test item

Procedure control

Toxicity control

Replicate no.

Replicate no.

Replicate no.

1

2

1

2

1

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

0

3

1

-

-

1

1

1

1

1

-

-

1

0

1

0

1

-

-

0

0

0

0

0

-

-

0

0

0

0

1

-1

-

-

-1

-1

-1

-1

-2

-

-

-1

-2

-1

-2

-2

-

-

-2

-2

-2

-2

-2

-

-

-2

-2

-2

0

11

52

-

-

73

76

79

80

81

-

-

85

87

88

89

90

-

-

92

92

93

93

93

-

-

93

94

94

0

11

52

-

-

69

73

76

78

79

-

-

83

84

86

87

88

-

-

91

91

91

92

91

-

-

92

92

92

0

4

23

-

-

28

29

30

31

32

-

-

34

35

36

36

37

-

-

38

38

39

39

39

-

-

39

39

39

Mean (28d)

-1**

93

Not applicable

* Corrected for the mean oxygen uptake of the inoculum controls

** Negative value due to higher oxygen consumption in the inoculum controls than in the test flasks with test item.

Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
The test substance was not biodegradable under the test conditions within 28 days. The substance is not considered readily biodegradable.
Executive summary:

This study was performed according to OECD Guideline 301F, EU Method C.4-D and GLP statement, to assess the ready biodegradability of the test substance following the BOD (biochemical oxygen demand) under define conditions over a period of 28 days.

In the procedure controls, the reference substance was degraded by an average of 87% by exposure day 14, and reached an average biodegradation of 93% by the end of the test (day 28), thus confirming suitability of the activated sludge.

In the toxicity control, containing both the test substance and the reference substance sodium benzoate, the test substance had no inhibitory effect on the activity of activated sludge microorganisms at the tested concentration of 100 mg/L.

The BOD of the test substance in the test media was in the nominal range found for the inoculum controls. Consequently, the test substance was not biodegradable under the test conditions within 28 days. The substance is not considered readily biodegradable.

All validity criteria were fulfilled and no deviations were observed.

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
From 12 Nov. 2009 to 14 Dec. 2009
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
This study was performed according to OECD Guideline 301F and GLP statement. All validity criteria were fulfilled and no deviations were observed. This study is considered reliable without restriction.
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Version / remarks:
1992
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 inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Collectd from the aeration tank of Shenyang North Sewage Treatment Center before 5 days of the test start. This plant is a main sewage plant in Shenyang for domestic waste treatment.

On the day of sample collection, removed coarse particles by filtration through a fine sieve (20 meshes) and settled the sample. After discarding the supernatant, suspended the concentrated sludge in mineral medium to yield a concentration of 3-5 g suspended solids (SS)/L and kept the sludge aerobic thereafter. On the day of the test beginning, a small amount of the sludge was weighed and dried. From this result, the added amount of wet sludge was calculated.
Duration of test (contact time):
28 d
Initial conc.:
97.69 mg/L
Based on:
ThOD/L
Initial conc.:
93.87 mg/L
Based on:
ThOD/L
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: Same as guideline.
- Test temperature: 20 +/- 0.5°C
- pH: 7.46 - 7.61
- pH adjusted: yes
- Aeration of dilution water: no data
- Suspended solids concentration: 30 mg SS/L
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 157 mL BOD bottles
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: no data
- Method used to create anaerobic conditions: not applicable
- Measuring equipment: Biochemical incubator Lovibond ET 636
- Other: For each BOD bottle, a magnetic stirring rod was added. 5 drops of KOH solution were placed into the seal gasket and the gasket inserted in the neck of the bottle. The BOD sensors were screwed into the sample bottles and the bottles placed in the bottle rack. The BOD system in the biochemical incubator was kept at constant temprature (20 +/- 0.5°C) and the measurement of oxygen uptake started under conditions of darkness. The oxygen uptake for the six bottles was read directly.

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes, 2
- Abiotic sterile control: no
- Toxicity control: yes, 1
- Other: Procedure control yes, 1
Reference substance:
benzoic acid, sodium salt
Preliminary study:
Not applicable
Test performance:
This study is valid.
Key result
Parameter:
% degradation (O2 consumption)
Value:
-1
Sampling time:
28 d
Details on results:
See tables 5.2.1/2 and 5.2.1/3 in "Any other information on results incl. tables".

The percentage biodegradation of toxicity control was 38% within 14 days and the value exceeded 25% based on total ThOD, which indicated that the test substance added to the inoculated mixture could not be assumed to be inhibitory.
Results with reference substance:
The percentage degradation of sodium benzoate exceeded 60% at the second day and reached to 85.6% at the 14 days, which achieved the requirement of the guideline.

Table 5.2.1/2: BOD results of the test substance and reference

Day

BOD (mg/L)

Inoculum control (R1)

Inoculum control (R2)

Test substance (R1)

Test substance (R2)

Toxicity control

Procedure control

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

3

5

6

7

6

7

8

8

8

8

9

9

9

10

11

12

11

11

12

12

11

12

13

12

13

12

13

13

2

3

3

4

4

5

6

6

6

6

7

8

7

9

9

10

10

10

10

10

10

10

11

11

11

12

12

11

0

2

2

3

3

4

4

5

5

5

6

5

5

5

7

7

8

7

8

7

8

8

8

8

9

9

10

10

1

2

3

4

4

5

5

5

6

6

5

5

6

6

6

7

8

8

9

9

10

10

11

12

12

12

12

12

43

58

64

72

74

77

78

78

81

81

82

82

82

83

85

86

87

87

87

86

87

88

88

88

89

89

89

89

41

61

63

73

74

78

79

80

83

83

85

87

88

88

91

92

92

92

92

92

92

92

95

94

95

94

95

96

Table 5.2.1/3: Biodegradation results of the test substance and reference

Day

Biodegradation (%)

Test substance

Procedure control

Toxicity control

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

-2.1

-2.1

-2.1

-2.1

-1.6

-1.6

-2.6

-2.1

-1.6

-1.6

-2.6

-3.7

-2.6

-4.2

-3.7

-4.2

-2.6

-3.1

-2.6

-3.1

-1.6

-2.1

-2.6

-1.6

-1.6

-1.6

-1.6

-1.0

42.0

62.2

63.8

73.6

75.3

78.5

78.5

79.6

82.9

82.9

84.0

85.6

87.3

85.6

88.4

88.4

88.9

88.9

88.4

88.4

88.9

88.4

90.5

90.0

90.5

89.5

90.0

91.6

21.0

27.9

30.8

34.4

35.7

36.7

36.7

36.7

38.3

38.3

38.3

38.0

38.3

38.0

38.8

38.8

39.6

39.6

39.3

38.8

39.6

39.8

39.3

39.6

39.8

39.8

39.6

39.8

Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
The test substance was not biodegradable under the test conditions within 28 days. The substance is not considered readily biodegradable.
Executive summary:

This study was performed according to OECD Guideline 301F and GLP statement, to assess the ready biodegradability of the test substance following the BOD (biochemical oxygen demand) under define conditions over a period of 28 days.

The test substance was added to the culture medium at a level of 97.69 and 93.87 mg ThOD/L, respectively. The percentage biodegradation in activated sludge after treatment of 28 days averaged (n=2) -1%.

In the toxicity test, containing both the test substance and reference substance, 38% degradation was occurred within 14 days and the value exceeded 25% based on total ThOD, which indicated that the test substance added to the inoculated mixture could not be assumed to be inhibitory.

The percentage degradation of sodium benzoate exceeded 60% at the second day and reached to 85.6% at the 14 days. The difference of replicate values of the oxygen consumption of the test substance at the end of the test was less than 20%. All validity criteria were fulfilled and no deviations were observed.

In conclusion, the substance is not considered readily biodegradable.

Endpoint:
biodegradation in water: inherent biodegradability
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
From 3 February 2011 to 17 March 2011
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
This study was performed according to OECD Guideline 302B, EU Method C.9 and US EPA OPPTS 835.3200 with GLP statement. All validity criteria were fulfilled and no deviations were observed. This study is considered reliable without restriction.
Qualifier:
according to
Guideline:
OECD Guideline 302 B (Inherent biodegradability: Zahn-Wellens/EMPA Test)
Version / remarks:
1992
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.9 (Biodegradation: Zahn-Wellens Test)
Version / remarks:
No. 440/2008
Deviations:
no
Qualifier:
according to
Guideline:
EPA OPPTS 835.3200 (Zahn-Wellens / EMPA Test)
Deviations:
no
Principles of method if other than guideline:
Not applicable
GLP compliance:
yes (incl. certificate)
Remarks:
2010-10-29
Oxygen conditions:
aerobic
Inoculum or test system:
other: mixed population of activated sewage sludge microorganisms
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Aeration stage of the Servern Trent Water Plc sewage treatment pant at Loughborough, Leicestershire, UK, which treats predominantly domestic sewage.

The sample of activated sewage sludge was maintained on continuous aeration upon receipt. A sample of the activated sewag sludge was washed twice by settlement and resuspension in culture medium to remove any excessive amounts of dissolved organic carbon (DOC) that may have been present. A sub-sample of the washed sewage sludge was then removed and the suspended solids concentration determined.
This inoculum was used for preparation of the replicate control, standard and test item vessels and the single toxicity control vessel.
A further sub-sample of the washed sewage sludge was sterilised by autoclaving (120°C, 15 minutes) in order to prevent any viable organisms surviving that may degrade the test item. The sterilised inoculum was used for preparation of the abiotic control and abiotic test vessels and Sodium azide was also added to the abiotic vessels in order to prevent any other viable microorganisms surviving that may degrade the test item.
Duration of test (contact time):
28 d
Initial conc.:
100 mg/L
Based on:
other: Carbon
Parameter followed for biodegradation estimation:
DOC removal
Details on study design:
TEST CONDITIONS
- Composition of medium: the culture medium used was that recommended in the OECD Guideline.
- Test temperature: 20-23°C
- pH: The pH values did not fall below 6.7 in any culture vessel during the study and were readjusted to pH 7.4 on sampling days.
- pH adjusted: yes
- Suspended solids concentration: 300 mg suspended solids/L (inoculum to carbon ratio of 3:1)
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 3L glass culture vessels
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: constantly aerated with compressed air via narrow bore glass tubes
- Method used to create anaerobic conditions: not applicable
- Measuring equipment: Shimadzu TOC-Vcph TOC analyser
- Test performed in closed vessels due to significant volatility of test substance: The culture vessels were covered with glass lids to reduce evaporation
- Other: Each culture vessel was also stirred constantly by a magnetic stirrer

SAMPLING AND ANALYSIS
Sample (approximately 30 mL) were filtered through 0.45 µm Gelman AcroCap disposable filters. The first approximate 5 mL of filtrate was discarded. Samples were taken for analysis at 0 and 3 hours and on Days 1, 2, 7, 10, 14, 21, 27 and 28. Prior to sampling for analysis any losses due to evaporation were corrected by the addition of deionised water and any item adhering to the culture vessel resuspended. In order to minimise possible contamination by viable bacteria, all pH, dissolved oxygen concentration and temperature probes were rinsed with sodium azide solution (10 g/L) prior to placing in the abiotic vessels. The samples were analysed for DOC using Shimadzu TOC-Vcph TOC analyser. Samples (50µL) were injected into the Total Carbon (TC) and Inorganic Carbon (IC) channels of the TOC analyser. TC analysis is carried out at 680°C using a platinum catalyst and zero grade air as the carrier gas. IC analysis involved conversion by orthophosphoric acid at ambient temperature. Calibration was performed using standard solutions of potassium hydrogen phthalate and sodium carbonate in deionised water. Each analysis was carried out in triplicate.

CONTROL AND BLANK SYSTEM
- Control: in duplicate, consisting of inoculated culture medium.
- Reference substance: in duplicate, in inoculated culture medium to give a final concentration of 100 mg carbon/L.
- Toxicity control: one replicate, in inoculated culture medium to give a final concentration of 200 mg carbon/L.
- Abiotic control: one repliate, consisting of culture medium plus sterilised inoculum poisoned by the addition of 20 mL of a 10 g/L sodium azide solution.
- Abiotic test: one replicate, the test substance in culture medium plus sterilised inoculum at a concentration of 100 mg carbon/L poisoned by the addition of 20 mL of a 10 g/L sodium azide solution.
Reference substance:
diethylene glycol
Preliminary study:
Not applicable
Test performance:
This study is valid.
Key result
Parameter:
% degradation (DOC removal)
Value:
10
Sampling time:
28 d
Details on results:
See table 5.2.1/1 in "Any other information on results incl. tables".

The results of the abiotic test vessel showed no abiotic degradation/loss of the test substance over the test period.
The toxicity control attained 53% degradation after 14 days and 57% degradation after 28 days, therefore confirming that the test substance was not toxic to the sewage treatment microorganisms used in the study.
Results with reference substance:
Diethylene glycol attained 99% degradation after 14 days and 100% degradation after 28 days, thereby confirming the suitability of the inoculum and culture conditions.

Table 5.2.1/1: Percentage degradation values

Days

% degradation

Diethylene glycol

Test substance

Toxicity control

Abiotic test

1

2

7

10

14

21

27

28

9

10

93

100

99

100

100

100

3

6

6

2

11

10

11

10

3

0

48

44

53

55

58

57

0

0

0

3

11

0

1

0

Validity criteria fulfilled:
yes
Interpretation of results:
not inherently biodegradable
Conclusions:
The test substance attained 10% degradation after 28 days. Therefore, this substance cannot be considered as inherently biodegradable under the experimental conditions employed in this study.
Executive summary:

This study was performed according to OECD Guideline 302B, EU Method C.9 and US EPA OPPTS 835.3200 with GLP statement, to assess the inherent biodegradability of the test substance in an aerobic aqueous media.

The test substance, at a concentration of 100 mg carbon/L was exposed to activated sewage sludge microorganisms with culture medium in the dark at temperatures between 20 to 23°C for 28 days. Based on the results obtained from the pre-study solubility work, the test substance was prepared as a saturated solution with the aid of high shear mixing prior to dispersal in inoculated culture medium to give the required test concentration.

The degradation of the test substance was assessed by the determination of dissolved organic carbon removal. Control cultures with inoculum and the reference substance, diethylene glycol, together with an abiotic test vessel, abiotic control vessel and toxicity control were used for validation purposes.

The results of the abiotic test vessel showed no abiotic degradation/loss of the test substance over the test period. The toxicity control attained 53% degradation after 14 days and 57% degradation after 28 days, therefore confirming that the test substance was not toxic to the sewage treatment microorganisms used in the study. Diethylene glycol attained 99% degradation after 14 days and 100% degradation after 28 days, thereby confirming the suitability of the inoculum and culture conditions. All validity criteria were fulfilled and no deviations were observed.

The test substance attained 10% degradation after 28 days. OECD Guideline 302B does not give any definitive pass levels for test items, however, the "Summary of Considerations in the Report from the OECD Expert Group on Degradation and Accumulation" suggests that a figure of more than 20% biodegradation may be regarded as evidence for inherent, primary biodegradability. A figure of more than 70% mineralisation may be regarded as evidence of ultimate biodegradation.

The test substance cannot therefore be considered as inherently biodegradable under the experimental conditions employed in this study.

Description of key information

OECD Guideline 301F, EU Method C.4-D, GLP, key study, validity 1:

No biodegradation observed after 28 days.

Not readily biodegradable.

OECD Guideline 302B, EU Method C.9, US EPA OPPTS 835.3200, GLP, supporting study, validity 1:

10% degradation observed after 28 days.

Not inherently biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

Three valid studies are available to assess the biodegradability potential of the substance. One study is assessed as the key study (Memmert, 2009) and the two others as the supporting studies (Zhang, 2010 and Clarke, 2011).

The first study (Memmert, 2009), was performed according to OECD Guideline 301F, EU Method C.4-D and GLP statement, to assess the ready biodegradability of the substance following the BOD (biochemical oxygen demand) under define conditions over a period of 28 days.

In the toxicity control, the substance had no inhibitory effect on the activity of activated sludge microorganisms at the tested concentration of 100 mg/L. The BOD of the substance in the test media was in the nominal range found for the inoculum controls. Consequently, the substance was not biodegradable under the test conditions within 28 days, therefore is not considered readily biodegradable.

The second study (Zhang, 2010), was performed according to OECD Guideline 301F and GLP statement, to assess the ready biodegradability of the substance following the BOD (biochemical oxygen demand) under define conditions over a period of 28 days.

In the toxicity control, the substance had no inhibitory effect on the activity of activated sludge microorganisms at the tested concentration of 100 mg/L. The biodegradation of the substance in activated sludge after treatment of 28 days averaged -1%, therefore is not considered readily biodegradable. This study supports the result of the key study.

The third study (Clarke, 2011), was performed according to OECD Guideline 302B, EU Method C.9 and US EPA OPPTS 835.3200 with GLP statement, to assess the inherent biodegradability of the substance in an aerobic aqueous media.

In the toxicity control, the substance had no inhibitory effect on the microorganisms used in the study. The substance attained 10% degradation after 28 days. OECD Guideline 302B does not give any definitive pass levels for test substance, however, the "Summary of Considerations in the Report from the OECD Expert Group on Degradation and Accumulation" suggests that a figure of more than 20% biodegradation may be regarded as evidence for inherent, primary biodegradability. A figure of more than 70% mineralisation may be regarded as evidence of ultimate biodegradation. Therefore, the substance cannot be considered as inherently biodegradable under the experimental conditions employed in this study.

In conclusion, based on the key and supporting studies, the substance is not considered readily or inherently biodegradable. Therefore, the substance is considered persistent in the environment.