2-[4-[[2-(cyanoimino)hexahydro-4,6-dioxo-5-pyrimidyl]azo]phenyl]-6-methylbenzothiazole-7-sulphonic acid, compound with 2,2',2''-nitrilotris[ethanol] (1:1)

Biodegradation in water: screening tests

Description of key information

The ready biodegradability of the test substance was investigated in a study (BASF SE, 2017) according to the OECD guideline 301 B (1992). The test substance was biodegraded by 20 - 30 % over 28 days. The test substance is determined to be not readily but inherently biodegradable according to the OECD criteria.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

The ready biodegradability of the test substance was investigated in a study (BASF SE, 2017) according to the OECD 301 B (1992) under GLP conditions. The biodegradation of the test substance was followed by exposing it over 28 days in the activated sludge from a municipal sewage plant (Municipal waste water treatment plant Mannheim, Germany). The inoculum was collected from the aeration tank of the plant. A suitable aliquot of the activated sludge suspension was sieved by a finely woven mesh with a mesh size about 1 mm. At the day of exposure the suspension was washed one time with drinking water. After settling, the supernatant was discarded and the remaining sludge suspension was filled up with drinking water and the concentration of the sludge was adjusted to 6.0 g/L dry weight. Aliquots of 7.5 mL were added to the test vessels to obtain an activated sludge concentration of 30 mg/L dry weight. To reduce the content of inorganic carbon in the blank controls the activated sludge was aerated with carbon dioxide free air for about 48 hours at 22 ± 2 °C. 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. The TIC- and DOC-analyses were performed as repeat determination. 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. 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 TIC-value of the freshly prepared sodium hydroxide solution was determined and considered by the calculation of biogenic produced carbon dioxide amount. The initial concentration of the test substance was ca. 45 mg/L (corresponding to 20 mg/L TOC). As a reference compound (aniline) was tested simultaneously under the same conditions. In the toxicity control no inhibitory effect on the microorganisms was observed. In the procedure controls, the reference compound aniline was biodegraded by 91 % after 14 days of exposure.  The required pass level for ready biodegradability within a ten days window was not reached. It can be assumed that the degree of biodegradation was mainly caused by the by product in the test item (19.9 g/100 g tri ethanol amine). At the end of the test, after 28 days the test substance was biodegraded by 20-30 %. The test substance is determined to be not readily but inherently biodegradable according to the OECD criteria. The validity criteria were met.

 

In addition, a supporting study (BASF SE, 1996) was performed to assess the inherent biodegradability of the test substance. Activated sludge from a commercial wastewater treatment plant was used as inoculum. The test substance was available in a preparation, but the test substance concentration reported in the study was based on the active ingredient (0.99 mg/L measured). Test substance concentrations were measured at the beginning and at the end of the 3 hours test period. Two replicates were tested and the test substance concentration was measured using liquid chromatography. The measured concentrations were used to calculate the adsorption rate (22.2 %) instead of the elimination. The test was conducted according to OECD Guideline 302B but with several deviations (only 3 hours tested instead of 28 days, no measurement of DOC removal, no reference substance was used). In conclusion, the rate of bioelimination by adsorption was 22.2 %, but no conclusion on biodegradation rate was determined.Therefore the study was regarded as klimisch 2.