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Environmental fate & pathways

Biodegradation in water: screening tests

Administrative data

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2009-10-05 to 2009-12-15
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: OECD guideline compliant GLP compliant

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2009
Report Date:
2009

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 301 A (Ready Biodegradability: DOC Die Away Test)
Version / remarks:
as at 1992
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.4-A (Determination of the "Ready" Biodegradability - Dissolved Organic Carbon (DOC) Die-Away Test)
Version / remarks:
as at 2008
Deviations:
no
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): R-Pantolactone
- Physical state: white to yellowish crystalline mass
- Analytical purity: 99.6 %
- Lot/batch No.: Bx TL 00906092
- Expiration date of the lot/batch: June 2011
- Storage condition of test material: at room temperature, protected from sunlight

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: aerobic activated sludge from municipal STP (ARA Ergolz II, Füllinsdorf, Switzerland)
- Method of cultivation: not cultivated
- Storage length: not stored, freshly obtained sludge was used
- Pretreatment: sludge was washed twice with tap water by centrifugation, decantation of supernatant and resuspension
- Concentration of sludge: 4 g (± 10%) dry matter per litre
Duration of test (contact time):
21 d
Initial test substance concentration
Initial conc.:
51.1 - 51.7 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
DOC removal
Details on study design:
TEST CONDITIONS
- Composition of medium: mineral medium was prepared in accordance with the technical guideline
- Additional substrate: not applicable
- Solubilising agent (type and concentration if used): not applicable
- Test temperature: 22 to 24 °C
- pH: 7.3 to 7.4
- pH adjusted: no
- Suspended solids concentration: 30 mg/L
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 2000 mL Erlenmeyer flasks, final volume of test medium was 1000 mL
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: flasks were loosely covered with aluminium foil to allow air exchange between flasks and surrounding environment, contents were continuously stirred
- Measuring equipment: TOC analyser equipped with automatic sampler (Shimadzu TOC-5000A)
- Test performed in open system: yes

SAMPLING
- Sampling frequency: test item and inoculum control were sampled on days 0, 3, 7, 10, 14, 21; positive reference substance control was sampled on days 0, 3, 7, 14 and 21; toxicity control was sampled on days 0, 7, 14 and 21
- Sampling method: one sample of about 10 mL was taken from each test flask per sampling date; prior to sampling, losses by water evaporation were determined and were compensated by adding purified water
- Sample storage before analysis: samples were analysed immediately or stored at -2 to -4 °C for 24 hours

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Abiotic sterile control: no
- Toxicity control: yes
Reference substance
Reference substance:
acetic acid, sodium salt
Remarks:
for details see above under "reference substance"

Results and discussion

Preliminary study:
not applicable
Test performance:
- Biodegradation started between experimental days 3 and 7
- 70% DOC removal was seen during a 10-day window in the flasks with test substance and activated sludge
- Complete DOC removal was seen within a test period of 21 days
- Postive reference substance was degraded (> 90%) within seven days
- The substance was not inhibiting to the activity of the active sludge
% Degradationopen allclose all
Parameter:
% degradation (DOC removal)
Value:
56 - 67
Sampling time:
7 d
Parameter:
% degradation (DOC removal)
Value:
100
Sampling time:
14 d
Details on results:
See tables under "Any other information on results"

BOD5 / COD results

Results with reference substance:
The positive control substance was degraded by at least 90% with 7 days.

Any other information on results incl. tables

Table 1: Dissolved organic carbon concentrations (DOC) in the test flasks

Time (days)

Dissolved organic carbon (DOC) in mg/L1, 2

Test substance

Positive control

Inoculum control

Toxicity control

Replicate No

Replicate No

Replicate No

Replicate No

1

2

Mean3

1

2

Mean3

1

2

Mean

13

0

31.5

30.5

27.7

32.4

31.6

28.7

4.3

2.3

3.3

56.5

3

30.8

31.3

28.5

3.7

2.4

0.5

1.9

3.3

2.6

--

7

11.9

14.4

10.7

4.4

3.4

1.3

2.7

2.5

2.6

28.2

10

2.9

3.1

0.2

--

--

--

2.5

3.2

2.9

--

14

2.6

2.1

0.1

3.2

2.3

0.5

2.4

2.2

2.3

1.5

21

2.3

2.2

0.0

2.3

2.5

0.2

2.3

2.2

2.3

1.6

1) Mean values of at least triplicate measurements per sample; 2) Sampling was ended before 28 days because the biodegradation curve reached a plateau for three determinations; 3) Values corrected for the inoculum controls; -- not determined

Table 2: Percentage biodegradation in the test flasks

Time (days)

Percentage biodegradation1, 2

Test

Positive control

Toxicity control

Replicated No.

Replicated No.

Replicated No.

1

2

Mean

1

2

Mean

1

0

0

0

0

0

0

0

0

3

0

-6

-3

96

101

98

--

7

67

56

61

94

97

95

50

10

100

99

99

--

--

--

--

14

99

101

100

97

100

98

97

21

100

100

100

100

99

99

97

1) Corrected for inoculum controls; 2) Sampling was ended before 28 days because the biodegradation curve reached a plateau for three determinations; -- not determined

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The substance was found to be readily biodegradable in a valid study according to the DOC Die Away test.
Executive summary:

The ready biodegradability of the test substance R-Pantolactone was studied under GLP in accordance with OECD TG 301-A (DOC Die Away test). Non-adopted activated sludge freshly collected from a municipal STP treating mainly domestic sewage was used in the test, which was suspended in standard mineral medium prepared according to the guideline at a concentration of 30 mg/L suspended matter. The concentration of test medium in the flasks was about 50 mg/L. The study was conducted in 2-L Erlenmeyer flasks that were loosely covered during the test. The test volume of continuously stirred test medium was 1000 mL per flask, the test temperature was 22 to 24 °C and the test was performed in the dark. In parallel, flasks with the inoculum alone, with the positive control sodium benzoate and with a mixture of positive reference substance and test substance (toxicity control) were tested under similar conditions. The reference substance was degraded by more than 90% within 14 days and the test substance did not inhibit the activity of the activated sludge. The test was considered as valid. Biodegradation of the test substance commenced between day 3 and 7 and reached more than 70% within a 10-day window. Complete biodegradation of the test substance was observed within 21 days and the test was ceased as biodegradation reached a plateau for three consecutive measurements.