2,6-bis(1,1-dimethylethyl)-4-(phenylenemethylene)cyclohexa-2,5-dien-1-one

Toxicity to microorganisms

Administrative data

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP guideline study according to OECD 209

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1998

Report date:

1998

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

no

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

-

EC Number:

429-460-4

EC Name:

-

Cas Number:

7078-98-0

Molecular formula:

C21 H26 O

IUPAC Name:

2,6-bis(1,1-dimethylethyl)-4-(phenylenemethylene)cyclohexa-2,5-dien-1-one

Details on test material:

- Physical state: yellow crystalline solid
- Storage condition of test material: in the dark at ambient room temperature

Sampling and analysis

Analytical monitoring:

no

Test solutions

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
Five stock solutions of the test substance were prepared directly in the Erienmeyer test flask. The stock solutions were spaced by a factor of no more than 3.2. Each stock solution was prepared by adding the appropriate amount of test substance (0.0498 g,0.0161 g, 0.0054 g, 0.0018 g, and 0.0008 g) into the test flask and then bringing to volume with 100 mL of DI water.

Test organisms

Test organisms (species):

activated sludge

Details on inoculum:

Approximately 12 liters of secondary effluent were collected on August 20, 1998 from the Loxahatchee Environmental Control District
sewage treatment plant in Jupiter, Florida. The effluent was collected from a tank containing a mixed liquor suspended solids (MLSS) concentration of 4000 - 6000 mg/L. Following collection, the effluent was allowed to settle for 30 minutes and then the supernatant was decanted. The sludge was then centrifugated at 2500 rpm for 15 minutes and the supernatant was decanted again. The solid material was resuspended in tap water, centrifugated and decanted again. The latter procedure was repeated twice. A portion of the final sludge was weighed, dried and the water content of the
sludge was determined. The water content in the sludge was found to be 88.9%.
Based on this water content, a sludge suspension containing about 4.0 g dry material per liter was made up with DI water. This solution will give the -final sludge content of approximately 1.6 g/L in the test medium. Because the sludge suspension was not used on the day of collection, 50 mL of synthetic sewage was added to each liter of sludge and the sludge was kept aerated at 20°C until use.
Before use, the pH of the sludge was determined to be 7.95.

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test conditions

Test temperature:

20 °C

Nominal and measured concentrations:

Nominal: 1.6, 3.6, 10.8, 32.2 and 99.6 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 1000-mL Erienmeyer flasks
- Aeration: the contents in each flask were aerated using compressed air at an air-flow rate of approximately 0.5 liter/minute for 3 h.
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 2
- No. of vessels per reference substance control (replicates): 1

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: deionized water (DI water) from an ion exchange treatment system

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Results and discussion

Effect concentrations

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Results with reference substance (positive control):

EC50 (3h) = 19 mg/L
This EC50 value lies within the guideline recommended range of 5 to 30 mg/L.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

The inhibition of the degradation activity of activated sludge is not anticipated when introduced in appropriate low concentrations.