3,5,5-trimethylhexanal

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

December 2012 until February 2013

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

Guideline study according to GLP guidelines

Qualifier:

equivalent or similar to guideline

Guideline:

EPA OPPTS 835.3110 (Ready Biodegradability)

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

Qualifier:

equivalent or similar to guideline

Guideline:

EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

Dry weight of suspended solids: 4.06 g/I, diluted to 1.53 g/I
To obtain a concentration of 30 mg/I (dry weight) in 103 ml total volume (Flasks 17 and
18), 2.00 ml of sludge was added (inoculum).
To obtain a concentration of 30 mg/I (dry weight) in 255 ml total volume (Flasks 1, 2, 13
and 14), 5.00 ml of sludge was added (inoculum).

Duration of test (contact time):

48 d

Initial conc.:

30 mg/L

Based on:

DOC

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

Test temperature: 21.4 - 22.4°c
Test duration: 48 days

TEST CONDITIONS
- Composition of medium: The following stock solutions were prepared:
Solution A:
KH2P04
K2HP04
Na2HP04 · 2 H20
NH4CI
8.5 g
21.75 g
33.4 g
0.5 g
dissolved in water and made up to 1 litre.
Solution B:
27.5 g
dissolved in water and made up to 1 litre.
Solution C:
22.5 g
dissolved in water and made up to 1 litre.
Solution D:
FeCl3 · 6 H2O
HCI Cone.
0.25 g
one drop
dissolved in water and made up to 1 litre.

Mineral medium

Prepared by mixing 50 ml of solution A and 2000 ml deionised water, adding 5 ml of
each of the solutions B, C and D and making up to 5 litres with deionised water. The pH
is measured and if necessary adjusted to 7.4 ± 0.2 with phosphoric acid or potassium
hydroxide.
- Test temperature: 21°c - 22.4°c
- pH: 7.4
- pH adjusted: yes
- Suspended solids concentration: 4.06 g/I, diluted to 1.53 g/I

TEST SYSTEM
- Culturing apparatus:
- Number of culture flasks: 2
- Measuring equipment: Oxitop system
- Test performed in closed vessels due to significant volatility of test substance

SAMPLING
- Sampling frequency: everyday
- Sampling method: Oxygen uptakes read on the Oxitop controller

CONTROL AND BLANK SYSTEM
- Inoculum blank: 2

Reference substance:

benzoic acid, sodium salt

Remarks:

Sodium benzoate (Fluka, Buchs, Switzerland, Art. No. 71300), purity: min. 99.0%.

Test performance:

Everyday the oxygen consumption of each flask is recorded and correct temperature
and stirring are checked.
At the end of the test period (normally 28 days), the pH of each flask is measured again.

Parameter:

% degradation (O2 consumption)

Value:

79

Sampling time:

48 d

Key result

Parameter:

% degradation (O2 consumption)

Value:

80

St. dev.:

0

Sampling time:

28 d

Remarks on result:

other: 80% degradation after 28 days

Details on results:

Oxygen uptakes, as read on the Oxitop controller, are corrected to account for the small
differences between actual and nominal concentrations of test and reference
substances.
Oxygen uptake curves can be found in Appendix 1. Calculated % biodegradation curves
and detailed results are reported in Appendixes 2 to 4.
Degradation of sodium benzoate exceeded 40% after 7 days and 65% after 14 days:
the activity of the inoculum was thus verified (validity criterion).
The repeatability validity criterion (not more than 20% difference between replicates) is
fulfilled for the flasks containing test substance. Therefore, the test is considered valid.

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

Aldehyde C9 lsononylic undergoes 80% biodegradation after 28 days (79% after 48
days) in the test conditions. The 10-day window criterion is also fulfilled (10%
biodegradation on day 7 and 73% on day 17).
Aldehyde C9 lsononylic did not inhibit the intrinsic respiration of the inoculum at the test
concentration and was therefore considered to be non-toxic to the inoculum at the test
concentration.
Thus, Aldehyde C9 lsononylic should be regarded as readily biodegradable according
to this test.

Description of key information

According to test performed using OECD TG 301 F; the test substance showed 80% biogedradation afetr 28 days (79% after 48 days) . The 10- days window criterion is also fulfilled (10% biodegradation on day 7 and 73% on day 17. Thus the substance can be regarded as readily biodegradable according to the test results.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater

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