Strontium 3-hydroxy-4-[(1-sulfonato-2-naphthyl)azo]-2- naphthoate 5/2 hydrate

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:

04 December 2007

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

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Molecular weight: 553.05
CAS Number: 15792-20-8
Description: Red powder
Batch: 070711
Purity: >96.4%
Test substance storage: At room temperature in the dark
Stability under storage conditions: Stable
Expiry date: 11 July 2011

Analytical monitoring:

no

Details on sampling:

Not applicable

Vehicle:

yes

Remarks:

Milli-RO water

Details on test solutions:

The batch of R507-2 was a red powder with a purity of at least 96.4%.

Under the conditions of the present test R507-2 was hardly soluble in water. Therefore, the test concentrations were prepared separately in Milli-RO water (tap water purified by reverse osmosis; Millipore Corp., Bedford, Mass., USA). Initial loading rates of 200 mg/I were stirred for 24 hours in the test bottles. Subsequently, synthetic sewage feed and sludge were added (see section 6.4) resulting in a loading rate of 100 mg/I. This loading rate was tested in duplicate. Optimal contact between the test substance and test medium was ensured applying continuous aeration and stirring.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

Activated sludge obtained from a municipal sewage treatment plant: 'Waterschap de Maaskant', 's-Hertogenbosch, the Netherlands, receiving predominantly domestic sewage.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

3 h

Post exposure observation period:

Not applicable

Hardness:

Not mentioned in study report

Test temperature:

18.1 to 18.5°C

pH:

8.2

Dissolved oxygen:

8.5-9.5 mg/L

Salinity:

Not applicable, as freshwater study

Nominal and measured concentrations:

100 mg/L loading rate

Details on test conditions:

Vessels: All glass, approximately 300 ml oxygen bottles and 1 litre test bottles.

Air supply: Clean, oil-free air

Performance of the test: Following the 24 hours of stirring, the synthetic sewage feed (16 ml) and the activated sludge
(200 ml) were added to the test substance mixture. Milli-RO water was added to provide a final volume of 500 ml with a final test substance loading of 100 mg/I. The mixture was aerated during the contact time, using a pipette as an aeration device.

After the 3-hour contact time, a well mixed sample of the contents was poured into a 300 ml oxygen bottle, and the flask was sealed with an oxygen electrode connected to a recorder, forcing the air out of the vessel. Oxygen consumption was measured and recorded for approximately 10 minutes. During measurement, the sample was not aerated but continuously stirred on a magnetic stirrer.
The pH and temperature were determined in the remaining part of the reaction mixture.

This procedure was repeated for the duplicate concentration. Two controls without test substance were tested in each test series, one at the start and one at the end.

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Details on results:

No inhibition of respiration rate of the sludge was recorded at 100 mg R507-2 per litre. The duplicate measurement confirmed the result of the first measurement (values of -1 and 5% inhibition only were recorded). Therefore, no further testing was needed.
Hence, the EC50 of R507-2 exceeded 100 mg/I (based on nominal concentrations).

Results with reference substance (positive control):

5 mg/L: 30% inhibition
12 mg/L: 65% inhibition
30 mg/L: 84% inhibition

Controls (C) and R507-2 (T): pH, oxygen concentration, oxygen consumption and percentage inhibition of the respiration rate

 

Flask	Loading rate (mg/I)	Oxygen cone. at the start (mg 02/l)	Oxygen consumption (mg 02/1/h)	% Inhibition respiration rate	pH
T1	100	9.0	50	-1*	8.2
T2	100	9.2	47	5	8.2

*A negative value indicates stimulation of the respiration rate of the sludge. This value is considered as not significant.

 

Validity criteria fulfilled:

yes

Conclusions:

Under the conditions of this present test, R507-2 was not toxic to waste water (activated sludge) bacteria at a nominal concentration of 100 mg/I. Thus, the EC50 of R507-2 exceeded 100 mg/I (based on nominal concentrations).

Description of key information

Under the conditions of this present test, R507-2 was not toxic to waste water (activated sludge) bacteria at a nominal concentration of 100 mg/I.

Thus, the EC50 of R507-2 exceeded 100 mg/l (based on nominal concentrations).

Key value for chemical safety assessment

EC50 for microorganisms:

100 mg/L