Disodium 3-[[2,2'-dimethyl-4'-[[4-[[(p-tolyl)sulphonyl]oxy]phenyl]azo][1,1'-biphenyl]-4-yl]azo]-4-hydroxynaphthalene-2,7-disulphonate

Toxicity to microorganisms

Administrative data

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

documentation insufficient for assessment

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1990

Report date:

1990

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Version / remarks:

adopted April 4, 1984

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

Acid Red 111

IUPAC Name:

Acid Red 111

Test solutions

Details on test solutions:

The test aricle was dissolved in bidistilled water at a concentration of 500 mg/l.

Test organisms

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Source: ARA, Sissach/Switzerland
- Pre-treatment: 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 two times. An aliquot of the final sludge suspension was weighed, dried and the ratio of wet sludge (ml) to its dry weight (g) detrmined.
- Preparation: a volume of washed sludge suspension corresponding to 4.0 g dry material were made up with Soerensen buffer (pH: 7) to 1 litre. To that mixture, 50 ml OECD recommended synthetic sewage feed were added.
- Incubation: sludged was incubated overnight at 20-25 °C under aeration.

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test conditions

Test temperature:

22 °C

pH:

Starting pH 7.7 in all vessels.

Nominal and measured concentrations:

10 and 100 mg/l

Details on test conditions:

TEST SYSTEM
- Test vessel: glass-flasks (> 500 ml)
- Aeration: aeration with 0.2 l/minute, instead of 0.5 l/minute to prevent possible foam development.
- No. of vessels per concentration: 1 replicate
- No. of vessels per control: 2 replicates
- Synthetic sewage per vessel: 16 ml
- Activated sludge amount: 200 ml

MEASUREMENTS
After exposure period, the first sample was taken for oxygen measurement over a period up to 10 minutes. Thereafter, in 15 minutes intervals, the rest of the samples were submitted to measurement of oxygen concentration.
During measurement, the sample was not aerated but cotinuously stirred on a magnetic stirrer. The apparatus used for oxygen measurements was the WTW OXI 91.

VALIDATION OF THE TESTS
The tests are validated by testing a known standard, i.e.3,5-dichlorophenol. The related IC50-value should be in the range of 5 - 30 mg/l.
Furthermore, the variation between the two control samples (start, end) should not be greater than 15 %.

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Results and discussion

Effect concentrations

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:

The aeration of the test mediun with test article caused the solution to foam. The foam was coloured. Under these conditions, the respiration rate of the sludge was moderately inhibited (25.1 %) at the highest concentration of test item, i.e. 100 mg/l.

Results with reference substance (positive control):

At a concentration of the standard of 10 mg/l, the respiration rate was highly inhibited by 56.7 %. The IC50 was found to be about 15.1 rng/l. Almost complete inhibition (86.0 %) was observed at 50 mg/l.

Any other information on results incl. tables

Influence of test item and reference control on oxygen consumption of activated sludge.

Vessel	Oxygen consumption (mg O2/l/min)	Inhibition (%)	Starting pH
Control	0.88	--	7.7
Control	0.83	--	7.7
Mean	0.85 ± 0.025 (5.7 %)
Test item 10 mg/l	0.79	7.6	7.7
Test item 100 mg/l	0.64	25.1	7.7
3,5-dichlorophenol 3.2 mg/l	1.04	-21.6	7.7
3,5-dichlorophenol 10 mg/l	0.37	56.7	7.7
3,5-dichlorophenol 50 mg/l	0.12	86.0	7.7

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Remarks:

the IC50-value of positive control resulted in the range of 5 - 30 mg/l and the variation between the two control samples was lower than 15 %

Conclusions:

IC50 (3h) > 100 mg/l

Executive summary:

The inhibitory effect of test item on aerobic wastewater bacteria was investigated in a respiration test. The test article showed only a moderate inhibition (25.1 %) of the respiration rate up to a concentration of 100 mg/l.

The IC50 was determined to be higher than 100 mg/l.

Conclusion

IC50 (3h) > 100 mg/l