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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:
30 Apr 2018 - 14 Jun 2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2018
Report Date:
2018

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Version / remarks:
1992
Deviations:
no
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
liquid
Details on test material:
Appearance: Clear colourless to pale yellow liquid
Test item storage: In refrigerator (2-8°C)

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: Municipal sewage treatment plant 'Waterschap Aa en Maas', 's-Hertogenbosch, The Netherlands, receiving predominantly domestic sewage.
- Preparation of inoculum for exposure: The freshly obtained sludge was kept under continuous aeration until further treatment. Before use, the sludge was coarsely sieved (1 mm) and washed with mineral medium.
- Concentration of sludge: After pretreatment, the concentration of suspended solids (SS) was determined to be 3 g/L in the concentrated sludge as used for the test. The sludge was used as inoculum at a concentration of 1 mL per litre of mineral medium, leading to a final concentration SS of 3 mg/L.
Duration of test (contact time):
28 d
Initial test substance concentrationopen allclose all
Initial conc.:
30.6 mg/L
Based on:
test mat.
Initial conc.:
80 mg/L
Based on:
ThOD
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: Mineral medium, according to OECD301
- Test temperature: 22 - 24 °C
- pH: 7.8 - 7.9 at start, 7.7 - 7.8 at day 28
- pH adjusted: no
- Continuous aeration: yes
- Continuous darkness: yes
- Other: continuous stirring.

TEST SYSTEM
- Culturing apparatus: 500 mL brown colored glass bottles, fill volume 360 or 244 mL, in order to obtain the required headspace-to-volume ratio.
- Number of culture flasks/concentration: 2 containing test item and inoculum; 2 containing only inoculum (inoculum blank); 1 containing reference item and inoculum (procedure control); 1 containing test item, reference item and inoculum (toxicity control).
- Preparation of bottles: At the start of the test (day 0), test and/or reference item were added to the respective bottles. The volumes of suspensions were made up to 360 mL or 244 mL using inoculated mineral medium.
Rubber gaskets containing two pellets of sodium hydroxide were inserted into each bottle. Subsequently, each bottle was sealed by screwing an automated respirometer head on top.
- Method used to create aerobic conditions: continuous aeration
- Measuring equipment: Lovibond BD600-GLP manometric respirometry system, equipped with an inductive stirring system.
- Test performed in closed vessels due to significant volatility of test substance: yes
- Details of trap for CO2 and volatile organics if used: The CO2 produced in each test bottle reacted with the CO2 absorbent (Sodium hydroxide pellets) in the rubber gaskets.

MEASUREMENTS
- Measurements were recorded on day 0-3-7-11-14-18-21-25-28. After recording the oxygen consumption on day 28, the pH was determined in all test vessels.

CONTROL AND BLANK SYSTEM
- Abiotic sterile control: no
Reference substance
Reference substance:
other: 1-octanol

Results and discussion

% Degradation
Key result
Parameter:
% degradation (O2 consumption)
Value:
80
Sampling time:
28 d
Remarks on result:
other: Bottle A: 85%; Bottle B: 75%.
Details on results:
The relative biodegradation values calculated from the measurements performed during the test period revealed 85% and 75% biodegradation of 6-hexyltetrahydro-2H-pyran-2-one (delta undecalactone), for A and B, respectively (based on ThOD). Furthermore, biodegradation of 6-hexyltetrahydro-2H-pyran-2-one (delta undecalactone) of at least 60% was reached within a 10-day window.
In the toxicity control, more than 25% biodegradation occurred within 14 days (79%, based on ThOD). Therefore, the test item was assumed not to inhibit microbial activity.

BOD5 / COD results

Results with reference substance:
Functioning of the test system was checked by testing the reference item 1-octanol, which showed a normal biodegradation curve (88% biodegradation within 14 days).

Any other information on results incl. tables

Table 1: Comparison of Biodegradation of the Test Item in Bottles A and B

Day

Biodegradation (%)

Bottle A

Bottle B

Mean A and B

∆ A-B1)

0

1

0

1

1

3

33

34

33

1

7

68

66

67

1

11

76

73

74

3

14

79

74

77

5

18

79

74

76

5

21

79

74

76

5

25

84

75

79

9

28

85

75

80

10

1): Absolute difference in biodegradation between bottles A and B

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Remarks:
See 'overall remarks' for details on validity criteria
Interpretation of results:
readily biodegradable
Conclusions:
The test item was 80% biodegraded after 28 days, and reached at least 60% within a 10-day window. Therefore, the test item is considered readily biodegradable under the conditions of the Manometric Respirometry Test.
Executive summary:

In a Manometric Respirometry Test, according to OECD guideline 301 F and GLP principles, the test substance was assessed for its ready biodegradability. The test substance was tested in duplicate at a target concentration of 31 mg/L, corresponding to a ThOD of 80 mg O2/L. The exposure period was 28 days and two inoculum blanks, a positive control and a toxicity control were included. The test item was added directly into the test bottles. The test solutions were continuously stirred during the test to ensure optimal contact between the test item and test organisms. The test substance was 75% and 85% biodegraded, in the duplicate bottles measured. Furthermore, at least 60% biodegradation was reached within a 10 -day window. Based on the average biodegradation of 80%, the substance is classified as readily biodegradable in the Manometric Respirometry Test. The test substance was found not to inhibit microbial activity and all validity criteria were met, thus the study was considered to be valid and reliable without restriction.