Reaction mass of Disodium decyl(sulphonatophenoxy)benzenesulphonate and Disodium oxybis[decylbenzenesulphonate]

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

read-across based on grouping of substances (category approach)

Adequacy of study:

key study

Study period:

1998

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP, guideline study

Justification for type of information:

Please see read across justification document.

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

reference to other study

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

no

Remarks:

Not specified in report

Qualifier:

according to guideline

Guideline:

other: European Economic Community (EEC), EEC Directive 67/548 amended November 18, 1987 (87/302), Part C: Methods for the determination of ecotoxicity, Publication No. L133, 'Biodegradation: Activated sludge respiration inhibition test", adopted 5/30/88

Deviations:

no

Remarks:

Not specified in report

Principles of method if other than guideline:

Not applicable

GLP compliance:

yes

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material:
None

Analytical monitoring:

no

Details on sampling:

No data

Vehicle:

yes

Details on test solutions:

TEST SUBSTANCE CONCENTRATIONS
A stock solution of 0.5 g/L was prepared in Milli-Q water. Thorough mixing (vortex) was used to accelerate dissolving and to ensure homogeneity.
The pH of the stock solution was 7.5.

100 mg/L, corresponding to 100 ml of the prepared stock solution in 500 ml final volume, was tested in duplicate.

REFERENCE SUBSTANCE CONCENTRATIONS
A solution of 3,5-dichlorophenol (Aldrich, Cat. no. D 7,060-0, purity 97%) was prepared by dissolving 124.7 mg in 2.5 ml 1N NaOH, diluting it to
approximately 7.5 ml with Milli-Q water and adding under stirring 1 N H2SO4 to the point of incipient precipitation (approximately 2 ml of 1N H2SO4 was required). Finally the solution was diluted to 250 ml with Milli-Q water.
The pH was 7.8.
Three concentrations were tested: 3.2, 10 and 32 mg/ L .

Test organisms (species):

activated sludge, domestic

Details on inoculum:

Source: Municipal sewage treatment plant: 'Waterschap de Maaskant', 's-Hertogenbosch, the Netherlands.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

30 min

Hardness:

No data

Test temperature:

19-23C

pH:

7.1-7.3

Dissolved oxygen:

Not aerated during test

Salinity:

No data

Nominal and measured concentrations:

Nominal: 100 mg/L

Details on test conditions:

TEST SYSTEM
Test System: Micro-organisms in activated sludge.
Source: Municipal sewage treatment plant: 'Waterschap de Maaskant', 's-Hertogenbosch, the Netherlands.
Number of micro-organisms: Number of micro-organisms was determined as the amount of Mixed Liquor Suspended Solids (MLSS) per litre test medium.
Preparation of the sludge: The sludge was coarsely sieved and washed with tap-water. A small amount of the sludge was weighed and dried at ca. 105°C. From this result the amount of suspended solids was calculated: the level was 3.7 g/L of sludge.
The batch of sludge was used on subsequent days (maximum four days), therefore 50 ml of synthetic sewage feed was added to each litre of activated sludge at the end of each working day. The sludge was kept aerated at test temperature until use. Before use the pH was checked (measured value: 7.8 ) .
Rationale: Recognized by international guidelines as the recommended test system.

TEST PROCEDURE AND CONDITIONS
Contact time: 30 minutes, during which aeration and stirring took place.
Vessels: All glass, 500 ml beakers and 300 ml oxygen bottles.
Milli-Q water: Tap-water purified by reverse osmosis and subsequently passed over activated carbon and ion-exchange cartridges (Millipore Corp.,Bedford, Mass., USA).

Synthetic sewage feed:
16 g peptone
11 g meat extract
3 g urea
0.7 g NaCl
0.4 g CaCl2 .2H2O
0.2 g MgSO4 .7H2O
2.8 g K2HPO4

Dissolved in 1 L Milli-Q water and filtered.
The pH was 7.0.
Air supply: Clean, oil-free air
Oxygen meter: Oxygen electrode (Tri Ox EO 200, WTW, FRG) supplied with a recorder (Kipp BD40).
Performance of the test: The synthetic sewage feed (16 ml) and an adequate amount of the test substance solution were mixed and made up to 300 ml with Milli-Q water. Activated sludge (200 ml) was added and the mixture was aerated in a 500 ml beaker during contact time using a pipette as an aeration device.

Then 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 not to remain in the vessel. Oxygen consumption was measured and recorded for approximately 10 min. During measurement the sample was not aerated but continuously stirred on a magnetic stirrer.
The pH was determined in the remaining part of the reaction mixture.

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

Each batch of activated sludge was checked for susceptivity by testing the reference substance 3,5-dichlorophenol.
The flasks were filled up to 500 ml final volume with: 16 mls synthetic sewage feed and 200 ml activated sludge per vessel.

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Duration:

30 min

Dose descriptor:

NOEC

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth inhibition

Details on results:

The percent inhibition for both test substance vessels at a concentration of 100 mg/L was 4%.
No significant inhibition in respiration rate of the sludge was recorded at 100 mg DOWFAX DRY HYDROTROPE POWDER per litre. The duplicate measurement confirmed the result of the first measurement. Therefore no further testing was needed.

Acceptability of the test
The mean respiration rate of control 1 and 2 was 35 mg O2/L/hr , The difference between the controls was 6%.

The mean respiration rate of control 2 and 3 was 38 mg O2/L/hr . The difference between the controls was 8%.

The EC50 of 3,5-dichlorophenol was 9 mg/L (regression line : Y = 60.0313 X -5.8981).

Since all criteria for acceptability of the test were met, this study was considered to be valid.

Results with reference substance (positive control):

The percent inhibition for the reference substance at concentrations of 3.2, 10 and 32 mg/L was 26, 51 and 86%, respectively.

The EC50 of 3,5-dichlorophenol was 9 mg/L (regression line : Y = 60.0313 X -5.8981).

Reported statistics and error estimates:

None

None

Validity criteria fulfilled:

yes

Conclusions:

Under the conditions of this present test DOWFAX* DRY HYDROTROPE POWDER was not toxic to waste-water bacteria at a concentration of 100 mg/L.

Executive summary:

DOWFAX* Dry Hydrotrope Powder is the dry form of a diphenyloxide based anionic surfactant which consists of disodium di- and monohexyl (linear C6) diphenyloxide disulfonate. The material was investigated for possible bactericidal effects with the activated sludge inhibition assay according to the OECD Guidelines No. 209 and to Directive 67/548/EEC, ammended Nov. 18, 1987 (87/302), Part C.

The effect of the test material on the respiration rate of activated sludge from a municipal waste water treatment plant was determined by comparing the oxygen consumption of two parallel samples treated with 100 mg/L of the test material with two untreated control samples (oxygen determination at the start and at the end of the experiment). The oxygen consumption was measured with an oxygen electrode after an incubation period of 30 minutes at 20 C.

The susceptibility of the activated sludge was evaluated by the addition of 3,5-dichlorophenol (3.2, 10.0 and 32.0 mg/L).

The test substance at a concentration of 100 mg/Lshowed no significant inhibitory effect on aerobic waste water bacteria. The control with 3,5-dichlorophenol showed an EC50 value of 9 mg/L indicating suitability of the used test conditions.

Additional information

No testing data are available with Dowfax 3B2 on toxicity to STP microorganisms. However, reliable studies on the inhibition of respiration in activated sludge (OECD TG 209) are available with two other members of the category, including Dowfax 8390 and Dowfax 6CL. With Dowfax 6CL, no effect was observed at the single concentration tested, yielding a 30 min NOEC of 100 mg/L. In the case of Dowfax 8390, percent inhibition increased from 11% at 25 mg/L, to 26% at 200 mg/L, but showed no further increase up to 284 mg/L (highest concentration tested). A NOEC value for Dowfax 8390 was not observed.