Tetrasodium 3,3'-[carbonylbis[imino(5-methoxy-2-methyl-4,1-phenylene)azo]]bis(naphthalene-1,5-disulphonate)

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:

02-November 2016

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 (Carbon and Ammonium Oxidation))

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

not required

Vehicle:

no

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Name and location of sewage treatment plant where inoculum was collected: Severn Trent Water Plc sewage treatment plant, Loughborough, Leicestershire, UK
- Method of cultivation: used on day of collection (maintained on continuous aeration in the laboratory at a temperature of approximately 21 ºC)
- Pretreatment: none
- Initial biomass concentration: SS 3.0 g/L

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

21 ºC

pH:

6.6-7.5 (the pH at 1000 mg/L was adjusted to 7.1)

Dissolved oxygen:

5.8-8.1 (65-91% of saturation)

Nominal and measured concentrations:

Range finding study: 3 inoculum controls, 3 test concentrations (single at 10 and 100, triplicate at 1000 mg/L), 1 abiotic control, 3 reference substance controls (3.2, 10 and 32 mg/L dichlotophenol )
No main test performed

Details on test conditions:

TEST SYSTEM
- Test vessel: 0.5L glass
- Aeration: 0.5-1.0 L/min
- Biomass loading rate: inoculum concentration 3.0 g/L

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: deionized reverse osmosis water containing less than 1 mg/L Dissolved Organic Carbon

OTHER TEST CONDITIONS
- Adjustment of pH: at 1000 mg/L from 6.6 to 7.1
- Temperature: 21 °C

EFFECT PARAMETERS MEASURED : dissolved oxygen concentration over 30 seconds intervals over 5 minutes post exposure (10 minutes post exposure for positive controls)

TEST CONCENTRATIONS
- Range finding study: 10, 100 and 1000 mg/L
- Test concentrations: no main test performed

Reference substance (positive control):

yes

Remarks:

dichlorophenol

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Key result

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Details on results:

- Adsorption (e.g. of test material to the walls of the test container): none observed
- Blank controls oxygen uptake rate: 38-0-40.8 mg O2/L/h (Specific 26.30 mgO2/dry sludge weight/h)
- Coefficient of variation of oxygen uptake rate in control replicates: 3.09%

Results with reference substance (positive control):

EC50 5.8 mg/L ( 4.4 – 7.7 mg/L)

Reported statistics and error estimates:

NA

Oxygen Consumption Rates and Percentage Inhibition Values after 3 Hours Contact Time in the Range-Finding Test

Nominal Concentration (mg/L)		Initial O2 Reading (mg O2/L)	Measurement Period (minutes)	Final O2Reading (mg O2/L)	O2Consumption Rates (mg O2/L/hour)	% Inhibition
Control	R1	5.9	6	1.9	40.00	-
	R2	5.7	6	1.8	39.00	-
	R3	5.6	6	1.8	38.00	-
	R4	5.6	5	2.2	40.80	-
Test Item	10	5.2	5	1.9	39.60	0
	100	5.2	5	1.8	40.80	0
	1000 R1	5.0	5	1.9	37.20	6
	1000 R2	5.7	6	2.0	37.00	6
	1000 R3	6.1	7	2.1	34.29	13
3,5-dichlorophenol	3.2	6.9	10	2.5	26.40	33
	10	7.5	10	5.4	12.60	68
	32	8.2	10	7.5	4.20	89

 

R₁– R₄= Replicates 1 to 4

Validity criteria fulfilled:

yes

Remarks:

see remark on O2 consumption rate

Conclusions:

The NOEC for respiration inhibition of activated sludge is 1000 mg/L.

Executive summary:

In a test according to OECD 209, no inhibition of the respiration of micro-organism in activated sludge was observed at 10, 100 and 1000 mg/L. The NOEC is 1000 mg/L.

Description of key information

In a test according to OECD 209 (Envigo 2017), no inhibition of the respiration of micro-organism in activated sludge was observed at 10, 100 and 1000 mg/L. The NOEC is 1000 mg/L. This confirms the results of an earlier study (RCC 1989) where the inhibition of oxygen at 100 mg/L was 12.4% (IC50 is > 100 mg/L).

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

1 000 mg/L