Reaction mass of 2-[4-[(Hexahydro-2,4,6-trioxo-5-pyrimidyl) azo]phenyl]-6-methylbenzothiazole-7-sulphonic acid, compound with 2,2',2''-nitrilotris[ethanol] (1:1) and Lithium 2-[4-[(hexahydro-2,4,6-trioxopyrimidin-5-yl)azo]phenyl]-6-methylbenzothiazole-7-sulphonate

Biodegradation in water: screening tests

Description of key information

The test item was not readily biodegradable according to OECD criteria, but moderately/partially biodegradable in a carbon dioxide evolution test, since the pass level for ready biodegradability within a ten days window was not reached and the degree of biodegradation after an exposure period of 28 days was 20-30% CO2/ThCO2.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

The ready biodgeradability of the test item was assessed in compliance with GLP principles and according to the guidelines OECD 301 B and EU Method C.4 -C. Municipal activated sludge from a wastewater treatment plant was exposed to the test item for 28 days (test temperature: 22 ± 2° C) at the test concentration of 20 mg/L TOC, which corresponds to approximately 43 mg/L test substance. Additionally, a blank control (with inoculum, but without the test item), a positive control (with inoculum and the reference substance aniline) as well as an inhibition control (with inoculum, the test item and the reference substance) was performed. Aliquots of activated sludge suspension were added to all test vessels, to adjust the concentration of activated sludge to 30 mg/L dry weight. The pH-values in the test vessels were measured and adjusted to 7.4 ± 0.2, if necessary. The test was performed in 2 L incubation bottles filled up to a volume of 1.5 L. The bottles were connected to two serial scrubbing bottles (total volume 250 mL) filled with 100 mL 0.05 mol sodium hydroxide solution for the adsorption of carbon dioxide from biodegradation processes. The incubation bottles were stirred on magnetic stirrers; the aeration was performed with carbon dioxide free air at a flow of approximately 800 mL per hour. Usually twice a week the Total Inorganic Carbon (TIC) values of the adsorption solutions of the first trap were determined and used for the calculation of the produced carbon dioxide. After each sampling the second trap was moved forward and the new trap with fresh sodium hydroxide solution was placed into the second position. Each trap was analyzed separately. The measured amount of carbon dioxide at the end of the test was compared with the calculated maximal theoretical production (ThCO2) and indicated as biodegradation degree in percent. The degree of biodegradation of the reference substance after 14 days reached 101 % CO2/ThCO2 and the degree of biodegradation in the inhibition control after 14 days was 50 % CO2/ThCO2.

For the test item the pass level for ready biodegradability within a ten days window was not reached and the degree of biodegradation after an exposure period of 28 days was 20-30%. Therefore, the test item is not regarded to be readily biodegradable according to OECD criteria, but moderately/partially biodegradable. All validity criteria of the test guidelines were fulfilled.