A mixture of: isomers of 2-(2H-benzotriazol-2-yl)-4-methyl-(n)-dodecylphenol; isomers of 2-(2H-benzotriazol-2-yl)-4-methyl-(n)-tetracosylphenol; isomers of 2-(2H-benzotriazol-2-yl)-4-methyl-5,6-didodecyl-phenol. n=5 or 6

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

13.07. - 22.08.1990

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Comparable to guideline study, none GLP. Instead a centrifuged sludge a settled sludge was used.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: EEC L 133, p. 118-122 (adopted on 30. May 1988 )

Deviations:

no

GLP compliance:

no

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: not specified
- Controls: Blank (dechlorinated drinking water)

Test organisms (species):

activated sludge, domestic

Details on inoculum:

- Preparation of inoculum for exposure:
Activated sludge collected from the sewage treatment plant of CH-4153 Reinach, Switzerland on 06/08/90. The preparation was carried out according to the method described in the guideline. The sludge was separated from the aqueous layer by settling instead of centrifugation.
- Initial biomass concentration: The sludge concentration in the test bottles was 1.7 g/L (dry weight).

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

20 °C +/- 2°C during the study

Nominal and measured concentrations:

Nominal: 100, 32, 10, 3.2 and 1 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 250 mL BOD flasks with gas inlet
- Aeration: no data
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 2
- Biomass loading rate: 1.7 g/L (dry weight)

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: dechlorinated drinking water
- Intervals of water quality measurement: Oxygen consumption per hour in mg/L with a ORION - Electrode Type 97-08, ORION Microprocessor lonalizer 901 and plotted on a recorder.

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: test was performed in the dark

EFFECT PARAMETERS MEASURED
The inhibitions were calculated on the basis of the measured time depend oxygen consumption of a Blank and Test solution.

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenole

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth inhibition

Details on results:

- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: no
- Effect concentrations exceeding solubility of substance in test medium: no

Results with reference substance (positive control):

For the reference substance 3,5-Dichlorophenol an EC 50(3h) rating of 14.6 mg/L was ascertained.

Description of key information

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

Additional information

In a 3-hr  acute toxicity study sewage sludge  micro-organisms were exposed to the test item at nominal concentrations of 100 mg/L in accordance with OECD 209. The IC50 value based on respiration rate was 100 mg/L after a 3 h contact time.  This toxicity study is classified as acceptable and satisfies the guideline requirements for OECD 209 toxicity study.