Methyl toluene-4-sulphonate

Endpoint summary

Description of key information

The mean biodegradation of 10% of PTSM was reached at day 6 (ThOD_NH4). At the end of the 10-day window at day 16, the mean degradation of PTSM was 58% (ThOD_NH4) and therefore the 10 day window criterion was not passed. The mean biodegradation at test end after 28 days was 73% (ThOD_NH4).

Therefore, PTSM is considered to be readily biodegradable, but failing 10-day window.

Additional information

Summary

Title: PTSM: Ready Biodegradability in a Manometric Respirometry Test

 

Material and Methods:

Test Species: Aerobic activated sludge (microorganisms from a domestic wastewater treatment plant) was supplied by the sewage treatment plant of Rossdorf, Germany.

 

Test Design: The test item PTSM was investigated for its ready biodegradability in a Manometric respirometry test over a period of 28 days. The biodegradation was followed by the oxygen uptake of the microorganisms during exposure. As a reference item sodium benzoate was tested simultaneously under the same conditions as the test item, and functioned as a procedure control.

 

Endpoints: Degradation rate of test item calculated by the oxygen consumption of the aerobic activated sludge microorganisms after 28 days of incubation.

 

Test Item Loading Rate (initial concentration in medium C₀): 102.5 mg/L corresponding to an oxygen demand of about 184.9 mg/L (ThOD_NH4)

 

Reference Item: Sodium Benzoate

Reference Item Loading Rate: 103.3 mg/L corresponding to an oxygen demand of about 172.1 mg/L (ThOD_NH4)

 

Test Conditions: 22°C ± 1°C, darkness

 

Results:

Biodegradation of PTSM: The criterion for ready biodegradability under the conditions of a manometric respirometry test is the degradation of the test item of at least 60%, reached within a 10-day window; the 10-day window starts when the degradation of the test item reaches at least 10% degradation.

The mean biodegradation of 10% of PTSM was reached at day 6 (ThOD_NH4). At the end of the 10-day window at day 16, the mean degradation of PTSM was 58% (ThOD_NH4) and therefore the 10 day window criterion was not passed. The mean biodegradation at test end after 28 days was 73% (ThOD_NH4).

Therefore, PTSM is considered to be readily biodegradable, but failing 10-day window.

 

Biodegradation of Sodium Benzoate: The reference item sodium benzoate was sufficiently degraded to 93% after 14 days and to 102% after 28 days of incubation, thus confirming the suitability of the aerobic activated sludge inoculum used.

 

Biodegradation of the Toxicity Control: In the toxicity control containing both, the test item and the reference item sodium benzoate, 45% biodegradation was noted within 14 days and 68% biodegradation after 28 days of incubation. According to the test guidelines, the test item can be assumed to be not inhibitory to the aerobic activated sludge microorganisms because degradation was >25% within 14 days.