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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:
16 Nov - 14 Dec 2001
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: GLP Guideline study with acceptable restrictions: Inoculum is not specified.
Qualifier:
according to
Guideline:
other: Circular on Test Methods of New Chemical Substances (Japan), ready biodegradability test
Deviations:
no
GLP compliance:
yes
Remarks:
other: according to the Japanese GLP Standard
Oxygen conditions:
aerobic
Inoculum or test system:
not specified
Details on inoculum:
- Source of inoculum/activated sludge: purchased at Chemicals Evaluation and Research Institute, Japan
Duration of test (contact time):
28 d
Initial conc.:
100 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: medium as recommended in guideline
- Test temperature: 25 ± 1 °C

TEST SYSTEM
- Culturing apparatus: closed oxygen consumption measuring machine with 300 mL culture bottle
- Number of culture flasks/concentration: 3 (sludge + test sub.)

SAMPLING
- Sampling frequency: continuously
- Sterility check if applicable: no

CONTROL AND BLANK SYSTEM
- Inoculum blank: 1
- Abiotic sterile control: 1 (water + test sub.)
Reference substance:
aniline
Parameter:
% degradation (O2 consumption)
Value:
85
Sampling time:
28 d
Details on results:
A biodegradation of 85% was reached within a time period of 28 days. No 10-day window is required for this test. Hence, the substance is readily biodegradable according to OECD criteria.
Results with reference substance:
The oxygen consumption for aniline in the above used test system reached 57% and more than 60% degradation after 7 days and 14 days, respectively.

Table 1: Results of analysis of BOD, DOC and HPL

water + test sub.

Treatment (sludge + test sub.)

Theoretical Amount

Mean

(sample 1 – 3)

replicate 1

replicate 2

replicate 3

BOD*

[mg]

0.0

63.7

62.1

64.0

74.4

 

[% ]

-

86

83

86

 

85

DOC

[mg/L]

4.0

1.0

1.4

1.8

68.9

 

HPLC**

[mg/L]

65.4

1.7

3.2

1.7

100

 

[% ]***

35

98

97

98

 

98

*: Treatments were calculated by subtracting blank values.

**: Residue of test substance

***: Disappearance rate was calculated as followed: Residue percentage = (Theoretical amount - Residue amount) / Theoretical amount x 100. Residue percent of DOC was not calculated due to the low water solubility.

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable

Description of key information

Readily biodegradable: 85% (O2 consumption) in 28 days 

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

One study investigating the ready biodegradability of Propane-1,2,3-triyl 2-ethylhexanoate (CAS No. 7360-38-5) is available. The study was conducted by a Japanese authority according to the Japanese guideline “Circular on Test Methods of New Chemical Substances, ready biodegradability test” under aerobic conditions (METI, 2002). The inoculum was not specified. Based on O2 consumption a mean degradation of 85% was observed after 28 days. No 10-day window is required. Hence, the test substance is determined to be readily biodegradable according to OECD criteria.