4,7-dimethyloct-6-en-3-one

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:

The study was conducted between 22 December 1998 and 20 January 1999.

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Lot No.: 286608
Aspect: colourless to pale yellow liquid
Purity: 96.6% (GC)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

Fresh activated sludge from a biological waste water treatment plant treating predominantly domestic sewage (City of Geneva, Aire, Switzerland) was used.
The sludge is collected in the morning, washed three times in the mineral medium, by centrifuging at 1000 g for 10 minutes, discarding the supernatant and re-suspending in mineral medium) and kept aerobic until being used on the same day.

Duration of test (contact time):

28 d

Initial conc.:

100 mg/L

Based on:

test mat.

Details on study design:

A measured volume of inoculated mineral medium containing a known concentration of test substance (100 mg/l) as the nominal sole source of organic carbon is stirred in a closed flask at a constant temperature (± 1 °C) for up to 28 days. Evolved carbon dioxide is absorbed in sodium hydroxide pellets. The consumption of oxygen is determined by measuring the quantity of oxygen (produced electrolytically) required to maintain constant the gas volume in the respirometer flask. The amount of oxygen taken up by the microbial population during biodegradation of the test chemical (corrected for update by blank inoculum, run in parallel) is expressed as a percentage of ThOD (Theoretical Oxygen Demand, calculated from the elemental composition, assuming that carbon is oxidised to carbon dioxide and hydrogen to water).

Apparatus
The respirometer used during this study is an SAPROMAT D 12, made by J.M.VOITH GmbH, D-7920 Heidenheim, Germany.

Water
The water used during this study is deionised water containing less than 10 mg/L dissolved organic carbon.

Stock solutions of mineral components
The following stock solutions were prepared:
Solution A.
KH2PO4: 8.5 g
K2HPO4: 21.75 g
Na2HPO4•2H2O: 33.4 g
NH4Cl:0.5 g
Dissolved in water and made up to 1 L.

Solution B.
CaCl2: 27.5 g
Dissolved in water and made up to 1L.

Solution C:
MgSO4•7H2O: 22.5 g
Dissolved in water and made up to 1L.

Solution D:
FeCl3•6H2O: 0.25 g
HCl Conc.: One drop
Dissolved in water and made up to 1L.

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 L with deionised water. The pH is measured and if necessary adjusted to 7.4 ± 0.2 with phosphoric acid or potassium hydroxide.

Determination of the dry weight of suspended solids
The dry weight of suspended solids is determined by taking two 50 mL samples of the homogenised sludge, evaporating water on a steam bath, drying in an oven at 105 – 110 °C for two hours and weighing the residue.

Preparation of the flasks
Test substance samples (25 mg corresponding to 100.0 mg/L in 250 mL flask) are weighed in small aluminium boats and added directly to the test flasks of the SAPROMAT, whereas reference substance samples (sodium benzoate) are added as 1.0ml of a 25mg/ml solution in mineral medium.

All flasks are filled with 250 mL of mineral medium. Samples of test or reference substance are added. Then, a volume of suspended sludge corresponding to 7.5 mg dry weight (as determined from 3.6, generally 1 to 3ml) is added. Except when the test substance has an acid or alkaline character, the pH of each flask is not measured by assumed to be the same as the mineral medium in order not to remove any floating undissolved test substance from the test medium by dipping a glass electrode in it. Neutral test substances, even sodium benzoate, were shown not to affect the pH of the medium by more than 0.1 pH unit. About 2 g of soda lime is placed in an attachment of the stopper, the flasks are closed and placed in the water bath of the SAPROMAT. After temperature and pressure equiibration, the oxygen meters of the instrument are set to zero (time zero of the experiment).

Performance of the test
Every day 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.

Test conditions for the present study:
Activated sludge
Dry weight of suspended solids: 2.742 g/L.
To obtain a concentration of 30 mg/L (dry weight) in 250 mL flask, 2.74 mL of sludge is needed (inoculum).

Reference substance:

benzoic acid, sodium salt

Parameter:

% degradation (O2 consumption)

Value:

77

Sampling time:

28 d

Details on results:

Oxygen uptakes as read on the SAPROMAT meters, are corrected:
- by deducting the basic oxygen uptake of sludge (flasks 1/5 and 1/6)
- proportionally to account for the small differences between actual and nominal concentrations of test and reference substances.
The test substance undergoes 77 % biodegradation after 28 days in the test conditions.
The test substance did not inhibit the intrinsic respiration of the inoculums at the test concentration and was therefore considered to be non-toxic to the inoculums at the test concentration.
The test substance should be regarded as readily biodegradable according to this test.

Results with reference substance:

Degradation of sodium benzoate exceeded 40 % after 7 days and 65 % after 14 days. The activity of the inoculum was thus verified (validity criterion).

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

The ready biodegradability of Dimethyl Octenone was determined by the Manometric Respirometry Test according to the OECD Guidelines for Testing of Chemicals, Method No. 301F.
Dimethyl Octenone undergoes 77 % biodegradation after 28 days in the test conditions. Biodegradation starts on day 7 and reaches 72% at the end of the 10-day window (days 7 to 17).
Thus, Dimethyl Octenone should be regarded as readily biodegradable according to this test.
At the concentration used in the test (100mg/L), Dimethyl Octenone is not inhibitory to the micro-organisms.

Executive summary:

The ready biodegradability of Dimethyl Octenone was determined by the Manometric Respirometry Test according to the OECD Guidelines for Testing of Chemicals, Method No. 301F.

Dimethyl Octenone undergoes 77 % biodegradation after 28 days in the test conditions. Biodegradation starts on day 7 and reaches 72% at the end of the 10-day window (days 7 to 17).

Thus, Dimethyl Octenone should be regarded as readily biodegradable according to this test.

At the concentration used in the test (100mg/L), Dimethyl Octenone is not inhibitory to the micro-organisms.

Description of key information

Dimethyl octenone undergoes 75% biodegradation after 28 days in the test conditions.

The 10-day window criterion is also fulfilled (biodegradation starts on day 7 and reaches 72% at the end of the 10 day window (days 7 to 17).

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

The Ready Biodegradability of Dimethyl octenone was determined by the Manometric Respirometry Test (OECD 301F).

Dimethyl octenone undergoes 75% biodegradation after 28 days in the test conditions. The 10-day window criterion is also fulfilled (biodegradation starts on day 7 and reaches 72% at the end of the 10 day window (days 7 to 17).

Dimethyl octenone did not inhibit the intrinsic respiration of the inoculum at the test concentration (100mg/l) and was therefore considered to be non-toxic to the inoculum at the test concentration.

Thus, Dimethyl octenone should be regarded as readily biodegradable according to this test.