Disodium 7-[[4,6-bis[(2-hydroxyethyl)amino]-1,3,5-triazin-2-yl]amino]-4-hydroxy-3-[[4-[(4-sulphonatophenyl)azo]phenyl]azo]naphthalene-2-sulphonate

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:

May 23rd, 1989

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Version / remarks:

adopted Aprll 4, 1984

GLP compliance:

no

Details on test solutions:

The test article was dissolved in distilled water at a concentration og 500 mg/l.

Test organisms (species):

activated sludge, domestic

Details on inoculum:

- Source: the tests were run with aeroblc actìvated sludge from a domestic waste-water treatment plant (ARA, Sissach/Switzerland).
- Pretreatment: the sludge was coarsely sieved, centrifuged, the supernatant liquld phase decanted, the solid material resuspended in tap water and again centrlfuged. This procedure was repeated a further two times.
- Preparation of inoculum for exposure: an aliquot of the flnal 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 suspenslon corresponding to 4.0 g dry material were made up with Soerensen buffel (pH 7) to t litre. To that mixture, 50 ml OECD recommended synthetic sewage feed were added. Thereafter, the sludge was incubated overnight at 20 - 25 °C under aeration.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

180 min

Test temperature:

22.0 °C

pH:

7.7

Nominal and measured concentrations:

100 and 10 mg/l nominal

Details on test conditions:

TEST SYSTEM
- Test vessel: glass-flasks (500 ml).
- Aeration: flasks were aerated with 0.2 l/minute.
- No. of organisms per vessel: 200 ml of activated sludge.
- No. of vessels per concentration: one replicate.
- No. of vessels per control: two replicates.
- No. of vessels per vehicle control: three concentrations tested (i.e. 50, 10 and 3.2 mg/l); one replicate each one.

TEST MEDIUM / WATER PARAMETERS
- Preparation of dilution water: according to the OECD guideline.

EFFECT PARAMETERS MEASURED
- Parameter: oxygen consumption.
- Sampling: after 180 minutes of aeration at 22.0 °C, the first sample was taken for oxygen measurement over a period of up to 10 minutes. Thereafter, in 15 minutes intervals, the rest of the samples were submitted to measurement of oxygen concentration.
Sampling was started with the control 1. Thereafter, the measurements were continued with the positive controls and the test article samples. Finally,
the oxygen consunption of control 2 was deternined.
- Measurements: oxygen consumption was measured over a period of 10 minutes. During measurement, the sample was not aerated but continuously stirred on a magnetic stirrer. The apparatus used for oxygen meesurements was the WTW OXI 91 (Wissenschaftlich-Technische Werkstaetten, Weilheim/Federal Republìc of Gernany).

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol sodium salt (500 mg/l)

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

Remarks:

respiration rate

Details on results:

The aeration of the test medium with test article caused the solutions to foam. The foam was coloured. Under these conditions, the respiration rate of the sludge was not inhibited (0 %) at the highest concentration of the test substance of 100 mg/l.

Results with reference substance (positive control):

- Results with reference substance: valid.
- Relevant effect levels: IC50 was found to be 10.6 mg/l. Almost complete inhibition (93.6 %) was observed at 50 mg/l.

Influence of the test substance on oxygen consumption of activated sludge

	Concentration [mg/l]	Oxygen consumption [mg O2/ l min]	Inhibition [%]	Starting pH
Control	-	0.46	-	7.7
Control	-	0.48	-	7.7
Mean± s		0.47 ± 0.01	4.3	-
Test item	100	0.47	0	7.7
Test item	10	0.48	-2.1	7.7
3,5-dichlorophenol	50	0.03	93.6	7.7
3,5-dichlorophenol	10	0.28	40.4	7.7
3,5-dichlorophenol	3.2	0.36	23.4	7.7

Validity criteria fulfilled:

yes

Remarks:

the two controls respiration rated were withing 15 % of each other and the IC50 (3h) of 3,5-dichlorophanol resulted to be in the accepted range 5 to 30 mg/l

Conclusions:

IC50 (3h) > 100 mg/l (nominal)

Executive summary:

Acute toxicity of the test substance to microorganisms was examined according to OECD guideline 209. This method determines the respiration rate (oxygen consumption) of an aerobic activated sludge. Aerobic activated sludge from a domestic waste-water treatment plant was used in the test. Two blank controls were used and 3,5 -dichlorophenol was employed as the reference standard. Nominal test substance concentrations were 100 and 10 mg/l.

Percentage inhibition by reference standards and test concentrations were determined as a function of mean oxygen consumption of the blank controls. The aeration of the test medium with test article caused the solutions to foam. The foam was coloured. Under these conditions, the respiration rate of the sludge was not inhibited (0 %) at the highest concentration of the test substance of 100 mg/l.

Conclusion

IC50 (3h) > 100 mg/l (nominal)

Description of key information

Not harmful/toxic for microorganisms.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

100 mg/L

Additional information

Acute toxicity of the test substance to microorganisms was examined according to OECD guideline 209. This method determines the respiration rate (oxygen consumption) of an aerobic activated sludge. Aerobic activated sludge from a domestic waste-water treatment plant was used in the test. Two blank controls were used and 3,5 -dichlorophenol was employed as the reference standard. Nominal test substance concentrations were 100 and 10 mg/l.

Percentage inhibition by reference standards and test concentrations were determined as a function of mean oxygen consumption of the blank controls. The aeration of the test medium with test article caused the solutions to foam. The foam was coloured. Under these conditions, the respiration rate of the sludge was not inhibited (0 %) at the highest concentration of the test substance of 100 mg/l (Ritter, 1989).