(R)-3,7-dimethyloct-6-enal

Biodegradation in water: screening tests

Administrative data

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2007-09-03 to 2007-10-05

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP-guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2007

Report date:

2007

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Test guideline 2

Qualifier:

according to guideline

Guideline:

EPA OPPTS 835.3110 (Ready Biodegradability)

Test guideline 3

Qualifier:

according to guideline

Guideline:

EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)

Test guideline 4

Qualifier:

according to guideline

Guideline:

ISO DIS 9439 (Ultimate Aerobic Biodegradability - Method by Analysis of Released Carbon Dioxide)

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Citronellal

EC Number:

203-376-6

EC Name:

Citronellal

Cas Number:

106-23-0

Molecular formula:

C10H18O

IUPAC Name:

3,7-dimethyloct-6-enal

Details on test material:

- Name of test material (as cited in study report): Citronellal
- Substance type: aldehyde
- Physical state: clear, colorless liquid
- Analytical purity: 96.2 area-% (BASF report No. 07L00174)
- Impurities (identity and concentrations): not reported
- Purity test date: not reported
- Lot/batch No.: 66086277L0
- Expiration date of the lot/batch: 2008-04-05
- Stability under test conditions: not reported
- Storage condition of test material: test substance stored at room temperature, under nitrogen and light exclusion

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Municipal activated sludge taken from the wastewater treatment plant of Mannheim(Germany). The inoculum was collected on 05 September 2007 from the aeration tank of the plant and aerated in the laboratory until use.
- Laboratory culture: no
- Preparation of inoculum for exposure: After collection, the inoculum was aerated in the laboratory until use. A suitable aliquot of the activated sludge suspension was sieved by a finely woven mesh (size: ca. 1 mm). After settling the supernatant was discarded and the sludge suspension was filled up with tap water. The sludge of the suspension was adjusted to a concentration of 6 g/L dw and then added to the test vessels to obtain a sludge concentration of 30 mg/L dry substance. Finally the activated sludge suspension in the test vessels was pre-aerated for about 24 h at 22 +/- 2°C.
- Pretreatment: no
- Concentration of sludge: 30 mg/L dw
- Water filtered: not reported

Duration of test (contact time):

28 d

Initial test substance concentration

Initial test substance concentration 1

Initial conc.:

ca. 26 mg/L

Based on:

test mat.

Initial test substance concentration 2

Initial conc.:

20 mg/L

Based on:

other: TOC

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: according to guideline
- Additional substrate: no
- Solubilising agent (type and concentration if used): no
- Test temperature: 22 +/- 2 °C
- pH: at the beginning: 7.4; at the end: 7.3 (in the test vessels containing test substance each)
- pH adjusted: no (not necessary based on pH measurement in one test vessel)
- Aeration of dilution water: yes
- Suspended solids concentration: 30 mg/L dw
- Continuous darkness: not reported

TEST SYSTEM
- Culturing apparatus: 2-L incubation bottles filled up to a volume of 1.5 L
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: aeration of test medium in the absence of the test substance
- Measuring equipment: TOC-analyser (Shimadzu TOC-5000A)
- Test performed in closed vessels: yes
- Details of trap for CO2 and volatile organics if used: The test vessels were connected to two serial wash bottles (total volume 250 mL) filled with 100 mL 0.05 M sodium hydroxide solution. Usually twice a week the TIC values of the adsorption solution of the first trap were determined. After each sampling the second trap was moved forward and the new trap with fresh sodium hydroxide solution was placed into the second position. Each trap was analyzed separately.

SAMPLING
- Sampling frequency: sampling was performed on day 0 and after 1, 3, 5, 7, 10, 12, 14, 17, 21, 24, 27, 28, and 29 d (d 29: on day 28 the test vessels were acidified and the aeration was continued for further ca. 24 h and the released carbon dioxide in both traps determined and added to the calculated amount of day 28).
- Sample storage before analysis: not reported

CONTROL AND BLANK SYSTEM
- Inoculum blank: performed
- Toxicity control: performed
- Other: functional/procedural control (reference substance) performed

Reference substance

Reference substance:

aniline

Results and discussion

% Degradation

Parameter:

% degradation (CO2 evolution)

Value:

83

Sampling time:

28 d

Remarks on result:

other: test item proved to be readily biodegradable and fulfilling the 10-d window criterion

Details on results:

Mean biodegradation degree of citronellal (% CO2/ThCO2)
3 d: 5%
5 d: 22%
10 d: 51%
12 d: 58%
14 d: 63%
21 d: 74%
28 d: 83

BOD5 / COD results

Results with reference substance:

The reference substance aniline was biodegraded by 78% after 14 d and by 88% after 28 d.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

Citronellal proved to be readily biodegradable and fulfilling the 10-d window criterion (83% biodegradation after 28 d).

Executive summary:

In a study conducted according to OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test), EPA OPPTS 835.3110 (Ready Biodegradability), EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test), and ISO DIS 9439 (Ultimate Aerobic Biodegradability - Method by Analysis of Released Carbon Dioxide), citronellal proved to be readily biodegradable and fulfilling the 10 -d window criterion. Citronellal was biodegraded by 5% (3 d), 22% (5 d), 63% (14 d), and 83% (28 d) based on the ratio of % CO2/ThCO2. The reference substance aniline was biodegraded by 78% after 14 d and by 88% after 28 d (mean values each). An inhibition of the inoculum by citronellal could not be observed in the toxicity control (test item and reference substance concentration: 20 mg/L TOC each; 62% biodegradation after 14 d).