Trisodium bis[4-[4,5-dihydro-4-[(2-hydroxy-5-nitrophenyl)azo]-3-methyl-5-oxo-1H-pyrazol-1-yl]benzene-1-sulphonato(3-)]cobaltate(3-)

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

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Version / remarks:

1984

GLP compliance:

no

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

The sludge was coarsely sieved, centrifuged, the supernatant liquid phase decanted, the solid material resuspended in tap water and again centrifuged. This procedure was repeated a further 2 times. An aliquot of the final sludge suspension was weighed, dried and the ratio of wet sludge (ml) to its dry weight (g) determined. Based on this ratio, a volume of washed sludge suspension corresponding to 4 g dry material were made up with Soerensen buffer (pH = 7) to 1 l. To that mixture, 50 ml OECD recommended synthetic sewage feed were added. Thereafter, the sludge was incubated overnight at 20-25 °C under aeration.

Water media type:

freshwater

Total exposure duration:

3 h

Test temperature:

22 °C

Dissolved oxygen:

aeration 0.2 l/min

Nominal and measured concentrations:

10, 100 mg/l

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Duration:

3 h

Dose descriptor:

IC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Details on results:

100 - (2Rs /(Rc1 + Rc2) × 100 = percent inhibition
Rs = oxygen consumption rate at tested concentration of test article
Rc1 = oxygen consumption rate, control 1
Rc2 = oxygen consumption rate, control 2

Results with reference substance (positive control):

IC50 = 9 mg/l (i.e. between 5 and 30 mg/l)

Validity criteria fulfilled:

yes

Remarks:

variance between controls 11.9 %; inhibitory effect of positive control within 5 and 30 mg/l.

Conclusions:

IC50 (3h) > 100 mg/l

Executive summary:

The inhibitory effect of test substance on aerobic waste-water bacteria was investigated in a respiration test.

No inhibition was seen up to 100 mg/l, thus IC50 > 100 mg/l upon a 3 -hour exposure.

Positive control 3,5 -dichlorophenol showed an IC50 = 9 mg/l.

Description of key information

IC50 (3h) > 100 mg/l

Additional information

OECD guideline 209.

No inhibition of the respiration rate was seen upon a 3 -hour exposure of an activated sludge at the highest tested concentration of 100 mg/l.