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Environmental fate & pathways

Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
26 Sep - 25 Oct 2016
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 310 (Ready Biodegradability - CO2 in Sealed Vessels (Headspace Test)
Version / remarks:
2014
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.29 (Ready Biodegradability - CO2 in Sealed Vessels (Headspace Test))
Version / remarks:
2014
Deviations:
no
GLP compliance:
yes (incl. certificate)
Remarks:
Swiss federal office of public health consumer protection directorate notification authority for chemicals
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: activated sludge of the local waste water treatment plant, ARA Birs, Birsfelden, Switzerland
- Storage conditions: aerated with CO2-free air at room temperature
- Storage length: holding period of two days prior to use
- Preparation of inoculum for exposure: washed three times by centrifugation, decantation of the supernatant liquid phase and resuspension of the solid material in tap water and finally in mineral medium
- Concentration of sludge: 4 mg dry material per liter
- Initial cell/biomass concentration: 4 mg dry material per liter
- Water filtered: no
Duration of test (contact time):
28 d
Initial conc.:
26.4 mg/L
Based on:
test mat.
Initial conc.:
20 mg/L
Based on:
TOC
Parameter followed for biodegradation estimation:
inorg. C analysis
Details on study design:
TEST CONDITIONS
- Composition of medium: according to the guidelines; pH adjusted to 7.7 to 7.4
- Test temperature: 20 °C
- pH: 6.8 (test item bottle), 7.3 (inoculum control bottle)
- Continuous darkness: yes

TEST SYSTEM
- Test vessel: 160 mL-Wheaton glass serum bottles (total volume), sealed with aluminium crimp caps with Teflon lined chlorobutyl septa
- Culturing condition: on an orbital shaker, shaking rate of 200 rpm in a temperature-controlled environment
- Number of culture flasks/concentration: 30 bottles (test item, inoculum control), 20 bottles (reference control), 12 vessels (toxicity control), at least three bottles were measured on each sampling timepoint
- Method used to create aerobic conditions: sealed bottles with a headspace of air
- Measuring equipment: inorganic carbon (IC) measured with TOC infrared gas analyzer, equipped with an automatic sampler (i.e. vario TOC cube from Elementar Analysensysteme GmbH, Germany)
- Test item application: injected into sealed bottles containing the inoculated mineral medium using a high precision syringe

SAMPLING
- Sampling frequency: Test item and inoculum control: Exposure Day 0, 2, 5, 7, 10, 14, 21 and 28; Procedure control: Exposure Day 0, 2, 7, 14 and 28; Toxicity control: Exposure Day 0, 14 and 28;
- Sampling method: 1 mL of 7M NaOH solution injected in each bottle and shaken for 1 h at the test conditions; test and control bottles were removed from the shaker and allowed to settle; suitable volumes of the liquid phase were withdrawn and subjected to IC analysis; 3 bottles were measured on each sampling occasion and 5 bottles from each series (except the toxicity control) were analyzed at the end of the test

CONTROL AND BLANK SYSTEM
- Inoculum blank: 3 replicates per sampling time (5 replicates at test end)
- Toxicity control: 26.4 mg/L test item and 26.1 mg/L reference item (corresponding to 20 mg TOC/L and 19.2 mg TOC/L); 3 replicates per sampling time (5 replicates at test end)
- Reference control: was tested with 26.1 mg/L 1-octanol (corresponding to 19.2 mg TOC/L); 3 replicates per sampling time (5 replicates at test end)

Reference substance:
other: 1-octanol
Key result
Parameter:
% degradation (CO2 evolution)
Value:
89
Sampling time:
28 d
Remarks on result:
other: 95 % confidence interval of ± 1.0 %
Details on results:
- pass level (10% degr.) reached after 14 days
- 10-day time window was fulfilled
Results with reference substance:
Functional control (1-Octanol): 86% degradation after 14 days
Toxicity control: 100% degradation within 14 days

Table 1: Percentage Biodegradation of the Test Item and the Reference Item 1-Octanol during the Incubation Period

Time (days)

% Degradation

Test item

Reference item

Replicate No.

Replicate No.

1

2

3

4

5

mean

1

2

3

4

5

mean

0

0.7

1.2

0.7

--

--

0.8

0.7

1.7

0.7

--

--

1.0

2

0.0

0.5

0.0

--

--

0.2

31.7

30.1

29.1

--

--

30.3

5

13.7

12.7

11.7

--

--

12.7

--

--

--

--

--

n.a.

7

33.6

46.1

31.6

--

--

37.1

71.2

67.6

72.2

--

--

70.3

10

59.5

50.4

57.5

--

--

55.8

--

--

--

--

--

n.a.

14

64.3

61.3

60.8

--

--

62.1

84.9

86.4

85.9

--

--

85.7

21

94.0

96.0

94.0

--

--

94.7

--

--

--

--

--

n.a.

28

88.1

88.6

90.6

88.1

89.6

89.0

98.1

97.1

98.1

94.5

92.4

96.0

(table continued below)

Time(days)

%Degradation

Toxicity control1

Replicate No.

1

2

3

mean

0

1.7

0.7

1.2

1.2

2

--

--

--

n.a.

5

--

--

--

n.a.

7

--

--

--

n.a.

10

--

--

--

n.a.

14

95.3

103.1

100.5

99.6

21

--

--

--

n.a.

28

116.3

106.4

107.5

110.1

1: Based on the added TOC from the reference item only.

--: No samples taken.

n.a.: Not applicable

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The substance was found to be readily biodegradable under the test conditions, with a mean percentage biodegradation of 89% at the end of the 28-day exposure period. The pass level for ready biodegradability (IC production of at least 60% of ThIC in a 10-day window within the 28-day test period) was reached on exposure day 14 (62%).

Description of key information

Readily biodegradable (89% within 28 d, OECD 310)

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

One experimental study is available investigating the biodegradability of the substance. The study was performed according to the OECD 310 (GLP). Non-adapted, domestic activated sludge from a sewage treatment plant was used as inoculum. After 28 d a mean degradation of 89% was recorded based on CO2-evolution (IC production increased from Day 2 until Day 21). Thus, the substance is considered to be readily biodegradable according to the OECD criteria. A toxicity control containing both, reference substance and test substance, did not indicate inhibitory effects to the inoculum (100% degradation after 14 d). All validity criteria of the study were met.