Pyridinium toluene-4-sulphonate

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method C.4-A (Determination of the "Ready" Biodegradability - Dissolved Organic Carbon (DOC) Die-Away Test)

Version / remarks:

May 2008

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 A (Ready Biodegradability: DOC Die Away Test)

Version / remarks:

July 1992

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 835.3110 (Ready Biodegradability)

Version / remarks:

1998

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): local wastewater treatment plant, ARA Birs (Birsfelden / Switzerland)
- Method of cultivation / Preparation of inoculum for exposure: The aerobic activated sewage sludge was washed three times by centrifugation, decantation of the supernatant liquid phase and resuspension of the solid material in tap water and finally in mineral medium. Aliquots of the homogenized final sludge suspension were weighed, thereafter dried and the dry weight of the suspended solids was determined.
Based on this determination, a calculated amount of wet sludge was suspended in mineral medium to obtain a concentration equivalent to 4 g dry material per liter. During the holding period of three days prior to use, the sludge was aerated at room temperature.

Duration of test (contact time):

28 d

Initial conc.:

30 mg/L

Based on:

DOC

Initial conc.:

54 mg/L

Based on:

test mat.

Remarks:

corrected for the water content

Parameter followed for biodegradation estimation:

DOC removal

Details on study design:

TEST CONDITIONS
- Composition of medium: mineral medium according to testing guidelines; analytical grade salts were dissolved in ultrapure water (ELGA PURELAB Option-Q water purification system)
- Test temperature: 22 °C
- pH: 7.4 at the start of the test and 7.0 to 7.4 at the end
- pH adjusted: no
- Suspended solids concentration: 30 mg/L
- Continuous darkness: no (diffuse light)

TEST SYSTEM
- Culturing apparatus: 2000 mL Erlenmeyer glass vessels, filled to a volume of 1000 mL, loosely covered with an aluminum cap to reduce losses by evaporation. The test vessels were incubated in an incubator with automatic temperature control and equipped with an orbital platform shaker, at approximately 130 rpm to prevent settlement of the inoculum and to maintain aerobic conditions.
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: orbital shaking at approximately 130 rpm
- Measuring equipment: TOC infrared gas analyzer equipped with an automatic sampler
- Test performed in open system: yes

SAMPLING
- Sampling frequency: Test item and inoculum control: Exposure Day 0, 2, 5, 7 and 8; procedure and toxicity control: Exposure Day 0, 2, 7 and 8. Sampling was ended before 28 days because the biodegradation curve reached a plateau for three determinations.
- Sampling method: Prior to sampling, water evaporation losses were determined by weighing the vessels and were compensated by adding purified water. Deposits on the test vessels were resuspended. Then, one sample of about 10 mL was taken from each sampled test vessel per sampling occasion. Samples were filtered through a 0.45 µm filter. The first 2-3 mL of the filtrate were discarded.
- Sample storage before analysis: Samples were immediately analyzed for DOC.

CONTROL AND BLANK SYSTEM
- Inoculum blank: 2 flasks containing inoculated mineral medium
- Reference: 2 flasks containing inoculated mineral medium and sodium benzoate (31 mg DOC/L)
- Toxicity control: 1 flask containing inoculated mineral medium, test material (31 mg DOC/L) and sodium benzoate (31 mg DOC/L)

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (DOC removal)

Value:

97

Sampling time:

8 d

Details on results:

The test was discontinued after 8 days since the test material was completely degraded.

Average biodegradation the toxicity control was >35 % by Exposure Day 8, indicating that the test substance was not inhibitory to activated sludge at the tested concentration of 54 mg/L.

For the individual results see attached document "Tables - DOC concentrations and % biodegradation.pdf"

Results with reference substance:

Average biodegradation of the reference item sodium benzoate was >60 % by Exposure Day 8, thus confirming suitability of the activated sludge, thus confirming the suitability of the used activated sludge inoculum (see "Attached background material" – "Tables - DOC concentrations and % biodegradation.pdf").

Validity criteria fulfilled:

yes

Remarks:

The difference between the degradation values of the replicate test vessels containing the test item was less than 20 % at the end of the test; the percentage degradation of the reference item reached > 70 % in a 10-day window by Day 14.

Interpretation of results:

readily biodegradable

Description of key information

Biodegradation in water: screening tests: aerobic biodegradation >90% (DOC) in 28 days (OECD 301A, EU C.4 -A)

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

[Type of water: freshwater]