Amides, C16-18 and C18-unsatd., N,N-bis(hydroxyethyl)

Biodegradation in water: screening tests

Description of key information

Based on available and reliable guideline-compliant studies, amides, C16-18 (even-numbered) and C18-unsatd., N,N-bis(hydroxyethyl) is considered to be readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

A study was conducted to determine the biodegradability of amides, C16-18 (even-numbered) and C18-unsatd., N,N-bis(hydroxyethyl) according to OECD guideline 301D (closed bottle test). A solution of the test substance at 2 and 5 mg/L was inoculated with activated sludge (1 ml/L) and placed in closed bottles in the dark for 28 days. Due to the low solubility of the test substance, a dispersing agent (Disponil nonylphenol + 9.5 EO +5EO (1:1)) was used. Degradation was followed by determining biological oxygen demand (BOD) on Days 7, 14, 21 and 28. The reference substance used was sodium benzoate. The reference substance reached the pass levels for ready biodegradability within 7 days. The mean degradation extent of the test substance was 60% within 28 days and the 10-day window criteria was met. Under the test conditions, the test substance was considered to be readily biodegradable (Richterich, 1997).

A study was performed to assess the ready biodegradability of amides, C16-18 (even-numbered) and C18-unsatd., N,N-bis(hydroxyethyl) according to the OECD guideline 301B and EU method C.4-C in compliance with GLP. The test substance was exposed to the activated domestic sewage sludge micro-organisms at a concentration of 10 mg C/L in sealed culture vessels in the dark at 21⁰C for 28 days. The test substance attained 62% degradation after 28 days but did not meet the 10-day window criterion. The degradation rate was also calculated on Days 0 and 28 for dissolved organic carbon (DOC) and was found to be 74 and 76%, respectively for the two replicates and 100% for the toxicity control. Further, the reference substance, sodium benzoate attained 99% degradation after 28 days, thereby confirming the suitability of the inoculum and test conditions. Under the test conditions, the test substance was considered to be readily biodegradable but failing the 10-day window (Mead C, 1997).

A study was conducted to determine the biodegradability of the test substance according to the Coupled Units test, as described in Directive 87/302/EEC. Two activated sludge pilot units were run in parallel. The test substance was added to the domestic sewage of one of the units, while the other received sludge alone. Only one unit was used for the determination of primary biodegradation. Dissolved organic carbon (DOC) was measured in the effluents. DOC reduction corresponded to 95.46% within 30 days. Therefore, under the study conditions, the test substance was considered to be ultimately biodegradable (Schöberl, 1991).