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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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Description of key information

water: >99% removal on average during the 3 weeks removal period; half-life 18-24 h; read across from MDEA Esterquat C16 -18 and C18 unsatd.

sediment: not required

Key value for chemical safety assessment

Additional information

As the substance is readily biodegradable, no simulation tests are required according to REACH regulation (Annex IX, 9.2.1., column II). However, simulation tests with teh closely related source substance MDEA Esterquat C16 -18 and C18 unsatd. are available. A justification for read-across is given in the Endpoint Summary "Biodegradation".

The removal of MDEA-Esterquat C16-18 and C18 unsatd. in an aerobic sewage treatment simulation test was investigated in a continuous activated sludge test system using influent and activated sludge collected from the wastewater treatment plant at Bochum (Germany) that receives primarily domestic wastewater. The study was conducted in accordance with OECD 303A, Simulation test - Aerobic Sewage Treatment, Activated Sludge Units and GLP standards. On average >99% parent MDEA-EsterquatC16-18 and C18 unsatd. was removed during the three weeks removal period. This was based on an average measured effluent concentration of 7.067 +/- 4.788 µg/L. However, the detection limit for the effluent samples was 12.72 µg/L. Based on the fluctuation in the effluent concentration and the highest effluent concentration observed (16 ug/L) the minimal removal during the test phase would have been 99.1%. The concentration of MDEA-EsterquatC16-18 and C18 unsatd. on the activated sludge solids was 50.43 µg/g over the three weeks removal period. The mass balance calculated in the 3 weeks removal period showed that more than 99% of the removed MDEA-Esterquat was eliminated by primary biodegradation.

The results of this experiment (in accordance with an early version of the newly adopted OECD 314) with non-adapted activated sludge indicated that 14C-MDEA-Esterquat C16-18 and C18 unsatd. (N-methyl group radiolabelled) and its hydrolysis products were fully biodegraded by microbes in unacclimated activated sludge. After 24 hr 20% of the parent remained, HP-1 (mono fatty acid ester) had virtually disappeared and HP-2 (diethanol dimethyl ammonium chloride) reached a maximum of 16%. The amount of activity incorporated into biomass was 25% and the amount trapped as 14CO2 was 35% during the same period. After seven days, the percentage of radioactivity converted to 14CO2 and incorporated into biomass totaled more than 75%, while the level of HP-2 remained at less than 5%. Based upon the kinetics of parent disappearance and metabolite production, it appears that MDEA-Esterquat C16-18 and C18 unsatd. is initially biologically hydrolyzed to HP-1, which very rapidly is hydrolyzed to HP-2, which is incorporated into biomass or evolved as 14CO2 without further accumulation of intermediates. HP-1 and HP-2 were both transient intermediates that did not accumulate. The half life for parent based upon the first order rate (k1) of primary degradation equaled 7 to 14 h using the equation t1/2=0.693/k1. Based on the kinetics of mineralization to 14CO2, the half life for mineralization equaled 18 -24 hr .

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