Potassium perchlorate

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:

November 03, 2017 - December 13, 2017

Reliability:

1 (reliable without restriction)

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

adopted July 22, 2010

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)

Version / remarks:

dated May 30, 2008

Deviations:

no

Qualifier:

according to guideline

Guideline:

ISO 8192 (Water quality - Test for inhibition of oxygen consumption by activated sludge for carbonaceous and ammonium oxidation)

Version / remarks:

ISO 8192:2007

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Vehicle:

no

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

Activated sludge, microorganisms from a domestic waste water treatment plant was supplied by the municipal sewage treatment plant Bensheim, Germany.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

20 +- 2 °C

pH:

7 - 8

Dissolved oxygen:

6.6 - 8.7 [mg O2/L]^2

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

383.5 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of respiration due to nitrification

Key result

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

< 10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of respiration due to nitrification

Key result

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

< 10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of heterotrophic respiration

Key result

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

< 10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Key result

Duration:

3 h

Dose descriptor:

other: EC20

Effect conc.:

14.8 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Details on results:

Total respiration:
In comparison to the inoculum controls the total respiration rate of the activated sludge was moderately inhibited at the three lower test concentrations (up to 100 mg/L) and strongly inhibited for test item concentrations of 320 mg/L and 1000 mg/L. The inhibition was between 18% and 28% at test concentrations of 10 mg/L, 32 mg/L and 100 mg/L. For the test item concentrations of 320 mg/L and 1000 mg/L the inhibition rates were 39.2% and 47.4%, respectively. Concentrations exceeding 1000 mg/L nominal were not tested. No clear concentration dependant relationship could be determined.

No clear concentration dependant relationship could be determined. Due to the higher inhibition at 10 mg test item/L than 32 mg test item/L, only the EC20 could be determined.
The 3-hour EC20 for total respiration was established to be 14.8 mg/L; the NOEC was determined to be lower 10 mg/L, as the inhibition in the lowest test item concentration of 10 mg/L was already 24.9%.

Potassium perchlorate had effects on the respiration (total respiration and nitrification respiration) of activated sludge microorganisms from 10 mg/L up to 1000 mg/L; doserelated effects could not be clearly observed over all test item concentrations. Therefore, the NOEC for total respiration, heterotroph respiration and nitrification respiration is below a test item concentration of 10 mg/L. Contrariwise, the inhibition of total respiration and heterotrophic respiration by Potassium perchlorate never reached 50%, suggesting that the EC50 values are above the highest tested concentration of 1000 mg/L.

Results with reference substance (positive control):

The 3-hour EC50 of the reference item 3,5-dichlorophenol for the total respiration was 4.0 mg/L and therefore in the range of 2 to 25 mg/L for the used activated sludge batch.

Validity criteria fulfilled:

yes

Conclusions:

Total respiration: The 3-hour EC20 for total respiration was established to be 14.8 mg/L; the NOEC was determined to be lower 10 mg/L, as the inhibition in the lowest test item concentration of 10 mg/L was already 24.9%.

Respiration without nitrification (Heterotrophic Respiration): The 3-hour EC20 for heterotrophic respiration was determined to be 13.7 mg/L; the NOEC was determined to be <10 mg/L.

Respiration based on nitrification: For the nitrification respiration, the 3-hour EC20 and EC50 were established to be 12.9 mg/L and 383.5 mg/L, respectively; the NOEC was determined to be <10 mg/L.

Executive summary:

The influence of the test item potassium perchlorate on the activity of activated sludge was evaluated by measuring the respiration rate under defined conditions. The respiration rate (oxygen consumption) of an aerobic activated sludge fed with a standard amount of synthetic sewage was measured in the presence of various concentrations of the test item after an incubation period of 3 hours.

Description of key information

Total respiration: The 3-hour EC20 for total respiration was established to be 14.8 mg/L; the NOEC was determined to be lower 10 mg/L, as the inhibition in the lowest test item concentration of 10 mg/L was already 24.9%.

Respiration without nitrification (Heterotrophic Respiration): The 3-hour EC20 for heterotrophic respiration was determined to be 13.7 mg/L; the NOEC was determined to be <10 mg/L.

Respiration based on nitrification: For the nitrification respiration, the 3-hour EC20 and EC50 were established to be 12.9 mg/L and 383.5 mg/L, respectively; the NOEC was determined to be <10 mg/L.

Key value for chemical safety assessment

EC50 for microorganisms:

383.5 mg/L