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Environmental fate & pathways

Biodegradation in water: screening tests

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Administrative data

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2012-2013
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2013

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Deviations:
yes
Remarks:
The test was performed over 43 d, instead of 28 d proposed by the Guideline. However, there is no influence on the integrity of the results.
GLP compliance:
yes (incl. certificate)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid: particulate/powder
Remarks:
migrated information: powder
Details on test material:
- Name of test material (as cited in study report): 6-[[(4-methylphenyl)sulphonyl]amino]hexanoic acid
- CAS: 78521-39-8
- Physical state: solid
- Appearance: white
- Purity: 99.24 % (HPLC)
- Moisture: 0.05 %
- pH (1% solution in H2O): 5.07

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: Activated sludge from wastewater treatment plant receiving predominantly domestic sewage (ČOV Spišská Nová Ves).
- Treatment of activated sludge: The sludge was used as collected but coarse particles were removed by settling for a short period, ca 15 minutes, and decanting the upper layer of finer solids and it was aerated by air without CO2 (CO2 was catched in the absorption flask with 0.05mol/L NaOH) (ca 2 L/minutes) at the test temperature until it was used in the test. The yield of suspended solids of the sludge in mineral medium was 4.32 g/ L.
- Initial cell/biomass concentration: The number of colony forming units (CFU) in the inoculum (used in the test) was 1.3x10^7 CFU (ml).
- Inoculum concentration in flasks of the experiment: concentration of suspended solids was 10.8 mg/L
Duration of test (contact time):
43 d
Initial test substance concentration
Initial conc.:
15.56 mg/L
Based on:
DOC
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Composition of medium: mineral medium according to OECD-GL 301 B
- Test temperature: 20.5 - 21.9 °C (within the range of 22 +-2°C)
- pH: 8.17 - 8.24
- pH adjusted: yes:
- test substance stock solution was prepared in mineral medium, pH adjusted to 8.0 with NaOH to achieve solubility of ASC plus
- the test substance solution (C0: 27 mg/L = DOC = 15.56 mg/L) with mineral medium was adjusted with NaOH to 7.4 without any precipitations
- Aeration: with CO2 free air
- Suspended solids concentration: 10.8 mg/L

TEST SYSTEM
The following seven bottles (3 l glass flasks, each fitted with aeration tube and outlet) were prepared:

Flask 1, 2 – containing test substance (pH 8.2) and inoculum (test suspension)
Flask 3, 4 – containing only inoculum (inoculum blank)
Flask 5 – containing reference compound and inoculum (procedure control)
Flask 6 – containing test substance and sterilising agent (abiotic sterile control)
Flask 7 – containing test substance, reference compound and inoculum (toxicity control)

- Method used to create aerobic conditions: bubbling CO2-free synthetic air through the suspensions at a rate 30 – 100ml/min
- Details of trap for CO2: absorption flask with 0.05 mol/L NaOH

CONTROL AND BLANK SYSTEM
- Inoculum blank: mineral medium and inoculum only
- Abiotic sterile control: contained test substance and sterilising agent: 1 ml/L of a solution containing 10 g/L HgCl2
- Toxicity control: contained mineral medium, test item, reference substance, inoculum
- Procedure control: mineral medium, reference substance (D+ glucose monohydrate) and inoculum
Reference substance
Reference substance:
other: D+ glucose monohydrate (C6H12O6.H2O)

Results and discussion

% Degradationopen allclose all
Parameter:
% degradation (CO2 evolution)
Remarks:
based on ThCO2
Value:
25.83
Sampling time:
28 d
Parameter:
% degradation (CO2 evolution)
Remarks:
based on ThCO2
Value:
42.54
Sampling time:
43 d
Details on results:
Degradation after 43 days:
- based on CO2 evolution: 42.54%
- based on DOC: 39.01 %
Based on measuring the test substance concentration by HPLC, the test substance was 2/ 0.2/ <0.1 mg/L at the 14th/ 21th/ 28th day of the test.

BOD5 / COD results

Results with reference substance:
85.95% degradation after 28 d.
96.28% degradation after 43 d.

Any other information on results incl. tables

Table 1 - Results of analyses based on TIC – % Degradation

Day

                 T-SL

Degradation % D = –––   x 100

                   ThCO2

D1

D2

D

(average)

1st

2.47

1.99

2.23

3rd

5.16

5.18

5.17

6th

5.89

6.80

6.35

8th

5.99

6.81

6.40

10th

7.91

5.96

6.94

14th

8.69

9.98

9.34

21st

20.28

22.35

21.32

28th

21.97

29.69

25.83

35th

23.89

29.61

26.75

43rd

AF I

34.93

35.27

42.54

(mean)

AF II

7.80

7.08

Table 2-Results of analyses of TIC , procedure control, Abiotic control and toxicity control

Day

                    T-SL

Degradation % D = –––   x 100

                       ThCO2

PC

AC

TC

1st

1.56

0.03

0.81

3rd

16.91

1.24

14.14

6th

38.07

1.23

37.82

 8th

41.35

1.36

37.19

10th

60.96

0.93

37.43

14th

78.07

1.42

39.59

21st

77.96

1.57

44.21

28th

85.95

1.75

52.92

35th

98.33

1.79

55.36

43rd

96.28

1.74

66.20

Table 3– Percentage of biodegradation by DOC

Flask No

DOC[mg/l]– the 1st

day

DOC[mg/l]– the 28thday

DOC[mg/l]– the 42ndday

% of biodegradation

  the 28thday 

% of biodegradation

the 42ndday

1

16.25

13.73

10.44

17.02

17.77

(mean)

38.49

39.01

(mean)

2

14.86

12.37

9.43

18.51

39.52

3

1.69

1.52

1.39

-

-

4

1.61

1.47

1.16

-

-

5

15.24

5.81

1.96

68.58

94.39

6

14.68

14.62

14.12

0.27

3.38

7

29.43

12.91

10.28

60.46

68.23

Table 4 - Results of analysis by HPLC

Concentration of the test substance ASC Plus [mg/L]

Flask No

the 1st

day

the 8th

day

the 14thday

the 21stday

the 28thday

the 35thday

the 42ndday

1

27.2

23.8

1.8

 0.2

< 0.1

< 0.1

< 0.1

2

26.6

22.5

2.1

0.2

< 0.1

< 0.1

< 0.1

6

27.8

27.7

26.3

27.8

27.4

27.9

27.6

 

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
inherently biodegradable
Conclusions:
Under the conditions of this study the test item is regarded as not readily biodegradable. Inherent biodegradation can be assumed.
Executive summary:

The test item ASC Plus was tested for ready biodegradability according to OECD 301 B (modified Sturm Test) using activated sludge of a sewage treatment plant receiving predominantly domestic sewage over 43 days.

Degradation after 28 / 43 days:

- based on CO2 evolution: 25.83% / 42.54%

- based on DOC: 17.77% / 39.01 %

Based on measuring the test substance concentration by HPLC, the test substance was 2/ 0.2/ <0.1 mg/L at the 14th/ 21th/ 28th day of the test.

Thus, the test item ASC plus was degraded. Results imply that within the test period the resulting metabolites were not completely degraded based on the CO2 development.

The test item is regarded as inherently biodegradable based on the conditions of this study.