Alcohols, C14-18 and C16-18-unsatd.

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

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study conducted to OECD and EC guidelines and in compliance with GLP

Qualifier:

according to guideline

Guideline:

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

Deviations:

yes

Remarks:

Water bath temperature marginal increased on two occasions, no impact on integrity of study findings

Qualifier:

according to guideline

Guideline:

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

Deviations:

yes

Remarks:

Water bath temperature marginal increased on two occasions, no impact on integrity of study findings

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge (adaptation not specified)

Details on inoculum:

A sample of activated sludge was obtained from a sewage treatment works, which treats predominantly domestic waste. At the time of collection, the
sludge was sieved (1 mm2) then transported to the laboratory and aerated until required.
The concentration of suspended solids in a blended and homogenous sample was determined before the start of the test. Aliquots (10 mL) of the sludge were filtered through dried and pre-weighed Whatman GF/C filters in triplicate, which were then dried again at approximately 105°C for one hour, allowed to cool in a desiccator and reweighed. The mixed liquor suspended solids (MLSS) content of the sludge was then determined and the volume required to give a solids level of 30 mg/L in test cultures was calculated.

Duration of test (contact time):

28 d

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

Reagents:
Sodium benzoate (for preparation of the reference substance stock solution).
Copper sulfate pentahydrate (for preparation of the 1 M electrolyte solution).
Potassium hydroxide pellets (for the preparation of the 2 M CO2 absorber solution).

In this test, a Co-ordinated Environmental Services (CES) Ltd automated respirometer and associated software was used to monitor the cumulative amount of oxygen consumed by the mixtures.

One day before test initiation, a volume (4 L) of mineral salts medium (MSM, was prepared (which contained the required amounts of mineral salts for 5 litres) and inoculated with freshly collected activated sludge.
The pH was then determined and adjusted to 7.57 with 5M HCl.
On the day of the test initiation, appropriate volumes of inoculated MSM were added to six amber glass culture bottles (500 mL) and the test substance or reference substance was added to appropriate bottles, which were then made to volume with pre-aerated ultrapure water.
A magnetic stirrer bar was added to each culture and eachbottle was fitted with an electrolytic cell assembly (containing the electrolyte, 1M copper sulfate solution, and the CO2 absorber, 5 mL of 2M potassium hydroxide) and connected to the respirometer.
The magnetic stirrer was set to give a vortex in each test mixture and the instrument was initiated.
Sodium benzoate (20 mL) was added as an aqueous stock solution (0.750 g/L) in MSM to the reference and inhibition assay cultures to give a final nominal concentration of 25 mg ThOD500 mL equivalent to 50 mg ThOD /L..
The pH of the cultures was measured and no adjustment was necessary.

Reference substance:

benzoic acid, sodium salt

Parameter:

% degradation (O2 consumption)

Value:

0

St. dev.:

0

Sampling time:

28 d

Details on results:

COD: Mean 178 mg O2/L, equivalent to ThOD of 3.56mg O2/mg for the test substance.
ThOD= 25 mg O2/500 mL
The blank-corrected oxygen demanded by the culture containing the reference substance had achieved 14.94 mg O2/500 mL or 60% of the ThOD (25 mg O2/500 mL) after 3 days of incubation. In the presence of UNJECOL 85AN, degradation of sodium benzoate had achieved 60% by Day 4. Cumulative levels of oxygen consumption by the controls after 28 days (24.77 and 20.83 mg O2/500 mL, equivalent to 49.54 and 41.66 mg O2/L) were considered to be acceptable for this assay system. These results confirm that UNJECOL 85AN was not inhibitory to the activity of the microbial inoculum and that the test was valid.

The pH of test mixtures ranged between 7.45 and 7.54 at the start of the test and 7.58 and
7.80 at the end. The temperature of the water bath ranged from 21.8 to 24.4C

Results with reference substance:

Sodium benzoate: C7H5O2Na MW = 144 ThOD: 1.67 mg O2/mg
Potassium hydrogen phthalate = 516 mg/O2/L

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

Mean oxygen consumption in mixtures containing the test substance was equivalent to 66% (25 mg O2/500 mL) after 28 days. UVCB substances that achieve ≥60% degradation within the 28 day test period in this type of test are considered to be readily biodegradable. Therefore, the test substance can be considered to be readily biodegradable under the conditions of this test.

Description of key information

‘Determination of Ready Biodegradability, Manometric Respirometry’ and OECD Procedure 301F

The test substance was considered to be readily biodegradable under the conditions of this test.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable