6-diazo-5,6-dihydro-5-oxonaphthalene-2-sulphonyl chloride

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:

2018-04-13 to 2018-05-16

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))

Version / remarks:

22 July 2010

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)

Version / remarks:

30 May 2008

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: As the test substance was known to be highly degradable in water, appropriate amounts of test substance were weighed and stored frozen overnight (-20ºC) until use. On the day of the study the test substance samples were added by direct addition to appropriate vessels immediately before the inoculum was added (to minimise degradation).
- Controls: pure water, synthetic sewage and inoculum, but without addition of test item

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

Test System: Activated sludge
Origin: Burley Menston Sewage Treatment Works (West Yorkshire, U.K.)
Reason for the selection: Predominantly domestic catchment
Pretreatment: The sludge was transported to the test facility in a closed container with an adequate headspace to prevent the sample from becoming anoxic. On arrival at the test facility, the sludge was aerated with a compressed air supply standardly delivered through an air pump.
The suspended solids concentration was determined gravimetrically following homogenisation and adjusted using dechlorinated tap water to 3 g/L (± 0.3 g/L), as necessary. The suspended solids content was determined to be 2.8 g/L for the definitive test.
The sludge was maintained at 20 ± 2°C with aeration. The sludge was collected on the 12 June 2018 and stored for 1 day before use for the definitive test. When stored, the sludge was maintained at 20 ± 2°C and fed daily with synthetic sewage concentrate at a rate of 50 mL/L.
The initial pHs of the sludge for the definitive was 6.81. The sludge used was adjusted with NaOH to a pH 7.55.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

3 h

Test temperature:

20.4°C

pH:

control: 7.15 to 7.19
test item: 7.11 to 7.54

Dissolved oxygen:

The dissolved oxygen level at the start of the measurement was low (ca 4 mg/L) and plummeted to just above 2 mg/L, before it levelled into a linear line, therefore, the rate has been calculated on a short linear line which extended below 2 mg/L.

Nominal and measured concentrations:

test item: 62.5, 125, 250, 500, 1000 mg/L (nominal)
positive control: 0.1, 2.0 and 40 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 250 mL glass conical flasks
- Type: open
- Aeration: yes
- No. of vessels per test item concentration (replicates): 3
- No. of vessels per positive control concentration (replicates): 1
- No. of vessels of control (replicates): 4
- Sludge concentration (weight of dry solids per volume): 3 g/L
- Nitrification inhibitor used: N-allylthiourea

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: dechlorinated tap water



EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
TEST CONCENTRATIONS
- Test item concentrations: 62.5, 125, 250, 500, 1000 mg/L (nominal)

Reference substance (positive control):

yes

Remarks:

3,5-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

Results with reference substance (positive control):

3,5-Dichlorophenol
EC50 = 12 mg/L (total respiration)

Validity criteria fulfilled:

yes

Conclusions:

Based on nominal test concentrations, the NOEC for nitrification, total respiration and heterotrophic respiration was estimated to be 1000 mg/L.

Executive summary:

The effects of the test substance, F6-chloride on the activated sludge micro-organisms of the biological (aerobic) stage of waste-water treatment plants was determined in accordance with OECD Guideline 209 (Adopted July 2010). Based on nominal test concentrations, the EC50 for total respiration, heterotrophic respiration and nitrification respiration were estimated to be >1000 mg/L respectively. Based on nominal test concentrations, the NOEC for nitrification, total respiration and heterotrophic respiration was estimated to be 1000 mg/L. All validity criteria were met therefore the test is considered valid.

Description of key information

The test item had no inhibiting effects on the respiration rate of activated sludge up to and including 1000 mg/L.

The NOEC was determined to be 1000 mg /L. The 3-hour EC50 value exceeded 1000 mg/ and could not be established.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

1 000 mg/L