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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; OECD Guideline 303A; RL2, GLP; read-across MDEA-Esterquat C16-18 and C18 unsatd.

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Additional information

Although not required under REACH Annex VIII following information about biodegradation simulation tests in water with the structurally similar source substance MDEA-Esterquat C16 -18 and C18 unsatd. will be given:

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 Guideline 303A, Simulation test - Aerobic Sewage Treatment, Activated Sludge Units and GLP standards. On average >99% parent MDEA-Esterquat C16-18 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-Esterquat C16-18 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 result of a second experiment (in accordance with an early version of the newly adopted OECD Guideline 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 .

In an influent die-away experiment, cold and radiolabelled MDEA-Esterquat C16-18 and C18 unsatd. were dosed at a combined concentration of 1 mg/L in raw domestic sewage. No mineralization was observed in the test system. Primary degradation was observed in the biotic treatment. The Rad-TLC analysis of the biotic treatment indicates that parent underwent degradation after a short lag period. The % parent remaining after 6, 24 and 48 h was 57%, 29% and 12%, respectively. Based on an initial recovery of ~70% from both treatments, it appears the half-life of parent in influent would be ~20 hr. Due to the very low recovery of radioactivity from the water extract after the 6 hr sampling interval and post lyophilization, the characterization of these extracts is inconclusive. However, it can be concluded that intermediates more polar than parent were present in the 24 and 48 samples because the majoirty of the radioactivity partitioned into the water phase and not the ethyl acetate phase. The study is not reliable due to methodological deficiencies. It can, however, be regarded as supportive study.