Guerbet alcohols, C24-26, branched and cyclic

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:

September 2019 to January 2020

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test (Carbon and Ammonium Oxidation))

Version / remarks:

July 22, 2010

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: The test itm was directly weighed into the test vessel and dstilled water was added.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Name and location of sewage treatment plant where inoculum was collected: Shenyang North Sewage Treatment Plant 1 (aeration tank)
- Preparation of inoculum for exposure: Coarse particles were remoed by settling for 15 minutes and by decanting the upper layer of finer solids. The sludge was centrifuged for 5 minutes at ca. 2500 rmp to produce a clear supernatant and pellet of sewage solids. The supernatant liquid was discarded and the sludge was re-suspended in chlorine-free tap water by shaking. The wash-water was removed by re-centrifuging and discarding again. After re-suspension of the sludge pellet in chlorine-free tap water, the solids concentration was determined by drying 4 replicates of 10 ml suspended sludge at 105°C for 1 hour and 48 minutes. From the measured results, the sludge was diluted further in chlorine-free tap water to obtain the required sludge solid concentration of 3.0 g/L. The activated sludge was fed with 50 ml/L syntheic sewage feed and continuously aerated at the test temperature (20.0-21.4 °C) overnight prior to use in the test. Before the inoculum was used in the test, the concentration of the sludge was determined again by the drying method, and the concentration was adjusted to 3.0 g/L.

Test type:

static

Water media type:

other: distilled water

Limit test:

no

Total exposure duration:

3 h

Test temperature:

20.1-21.4 °C

pH:

7.01-7.73

Dissolved oxygen:

60-70 %

Nominal and measured concentrations:

nominal

Details on test conditions:

TEST SYSTEM
- Aeration: clean oil-free air, flow rate 0.5 - 1 L/min
- No. of vessels per concentration (replicates): 1 (10, 100, 300 mg/L and reference substance) 3 (1000 mg/L)
- No. of vessels per control (replicates): 4 per concentration
- No. of vessels per abiotic control (replicates): 3
- Sludge concentration (weight of dry solids per volume): 3.0 g/L
EFFECT PARAMETERS MEASURED (with observation intervals if applicable): oxygen consumption
TEST CONCENTRATIONS
- Test concentrations: 0, 10, 100, 300, 1000 mg/L

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol (3,5-DCP)

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Key result

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

>= 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Details on results:

No oxygen uptake in the abiotic control. In the test item mixture, the average percentage inhibition was - 1.0% at 1000 mg/L (no significant inhibitory effect)
- Blank controls oxygen uptake rate: 23.6 mg(g*h) oxygen
- Coefficient of variation of oxygen uptake rate in control replicates: 8.1 %

Results with reference substance (positive control):

- Results with reference substance valid: yes
- Relevant effect levels: EC50= 8.8 mg/l

Validity criteria fulfilled:

yes

Conclusions:

The EC50 (3 h) of the test item for total respiratory inhibition to activated sludge was greater than 1000 mg/L.

Executive summary:

To investigate the toxicity to microorganisms an activated sludge respiration inhibition test was conducted. Activated sludge was incubated with test item at 4 different concentrations of up to 1000 mg/L. The rate of respiration of each incubation mixture was determined after the 3 hours exposure. Based on the results, there was no oxygen uptake in the abiotic control. In the test item mixture, the average percentage inhibition was -1.0 % at the concentration of 1000 mg/L. Therefore, the EC50 (3h) of the test item for total respiratory inhibition in activated sludge is greater than 1000 mg/L under the conditions of the study.

Description of key information

To investigate the toxicity of Guerbet alcohols, C24 -26, branched and cyclic to microorganisms an activated sludge respiration inhibition test was conducted. Activated sludge was incubated with the test item at 4 different concentrations of up to 1000 mg/L. The rate of respiration of each incubation mixture was determined after the 3 hours exposure. Based on the results, there was no oxygen uptake in the abiotic control. In the test item mixture, the average percentage inhibition was -1.0 % at the concentration of 1000 mg/L. Therefore, the EC50 (3h) of the test item for total respiratory inhibition in activated sludge is greater than 1000 mg/L under the conditions of the study.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

1 000 mg/L