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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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Description of key information

ased on the available studies on biodegradation, the substances are estimated to be readily biodegradable. The 10-days-window criterion should not be evaluated for a UVCB thus there is no requirement for performing a soil biodegradation test (Annex IX. 9.2.1.3). No simulation tests for degradation rates under environmental conditions are available for primary fatty amine ethoxylates but for a very similar substance (hexadecyl amine) and these results will be used for read-across to primary fatty amine ethoxylates (2EO). For soil and aerobic sediment this is a half-life value of 17 days at 12 °C.

In addition a waste water treatment simulation test was performed with 2,2’(octadec-9-enylimino)-bisethanol (25307-17-9). More than 99.999% removal was observed using specific chemical analyses (LCMS/MS) of the effluent during day 44 to 48 (n=5). Also  the sorption to sludge was measured and this accounted for 0.16 % of the total removal which means that 99.83% is removed by biodegradation.

Key value for chemical safety assessment

Half-life in freshwater:
15 d
at the temperature of:
12 °C
Half-life in freshwater sediment:
17 d
at the temperature of:
12 °C

Additional information

Biodegradation in a sewage treatment simulation test:

More than 99.999% removal is observed for 2,2’(octadec-9-enylimino)-bisethanol (25307-17-9) in waste water treatment simulation test. From this removal 99.83% is removed via biodegradation and 0.16 % via sorption. The test result can be used for the other primary fatty amine ethoxylates as a worst-case because all primary fatty amine ethoxylates

The removal ofoctadecenyl bis(2-hydroxyethyl)amine in biological treatment plants was simulated in a continuously-fed activated sludge (CAS) unit fed with domestic wastewater spiked with octadecenyl bis(2-hydroxyethyl)amine (AkzoNobel, 2010). Octadecenyl bis(2-hydroxyethyl)amine was exposed to micro-organisms maintained by addition of domestic wastewater in the CAS test. Octadecenyl bis(2-hydroxyethyl)amine was spiked at a nominal influent concentration of 50 mg/L (37.0 mg/L carbon; calculated) for a period of 48 days and included a control fed with domestic wastewater only.

The immediate high removal percentages can be attributed to adsorption and probably biodegradation. The mean removal percentage of octadecenyl bis(2-hydroxyethyl)amine calculated over 15 measurements obtained from day 34 to 48 of the test was 102±0.8% (95% confidence interval). These high removal percentages strongly indicate that octadecenyl bis(2-hydroxyethyl)amine is biodegraded completely. Formation of water soluble compounds during biological treatment of octadecenyl bis(2-hydroxyethyl)amine can be excluded. An accurate assessment of the removal of octadecenyl bis(2-hydroxyethyl)amine was established with specific analyses. The mean removal percentage of octadecenyl bis(2-hydroxyethyl)amine in the test unit was quantified from day 44 to 48 and was more than 99.999% usingoctadecenyl bis(2-hydroxyethyl) amineas representative component as a worst-case. These analyses demonstrate that the removal of octadecenyl bis(2-hydroxyethyl)amine is complete. Octadecenyl bis(2-hydroxyethyl)amine concentrations in the mixed liquid suspended solids (activated sludge) of the reactor sampled on days 47 and 48 were 3.2 mg/L. Mean removal percentages of octadecenyl bis(2-hydroxyethyl)amine from the influent through adsorption onto sludge assessed in two samples was therefore 0.16% demonstrating that octadecenyl bis(2-hydroxyethyl)amine is primarily removed by biodegradation.

In conclusion, the CAS test demonstrates thatoctadecenyl bis(2-hydroxyethyl)amine isalmost completely removed from the wastewater in conventional biological wastewater treatment plants.Octadecenyl bis(2-hydroxyethyl)amineis primarily removed by biodegradation.

 

Biodegradation in sediment:

Default half-life’s

For the derivation of the default half-life’s the bioavailability is taken into account via the sorption properties of the substance. This is realistic for soluble non-toxic substances. For poorly soluble/strongly sorbing substances however, the degradation rate in a standard ready test is limited by the dissolution rate and in many cases not 60% degradation is achieved within 28 days but in a slightly longer time frame. Such a substance is in fact completely degraded to CO2and H2O and thus completely biodegradable. The bioavailable fraction is readily biodegradable but the due to the stringency of the test setup the substance this cannot be observed.

The Kpsoil was determined as 4526 L/kg. The suggested maximum half-life for a readily degradable substance with a Kpsoil in the range >1000 and < 10000 L/kg is 3000 days for soil (at 12 ºC). These values are considered as extremely conservative but in the absence of measured data can be used in the exposure assessment as a worst-case. The half-life of the bioavailable fraction of primary fatty amine ethoxylates in the water phase of soils is expected to be in the order of a few days, which is based on experiments with dialkyldimethylammonium salts (van Ginkel et al, 2003).

Read across from primary alkyl amines

For hexadecylamine[1-14C] a substance which isvery similar to 2,2'-(C12-18 evennumbered alkyl imino) diethanol (CAS no 71786-60-2) there is an OECD 307 aerobic soil transformation study available and the results of this study will be used for read across to the primary alkyl amine ethoxylates for both the soil and sediment compartment. Although this C16 amine is strongly sorbing to soil (median Kp soil of 3875 L/kg at lowest measured concentration) the following half-life’s at 20 °C were determined for three soils: Soil 1 t1/2 = 9.0 d; Soil 2 t1/2 = 8.1 d; Soil 3 t1/2 = 8.9 d.

The median Half-life of 8.9 d at 20 °C corresponds to a median Half-life of 16.9 d at an environmental temperature of 12 °C (see REACH Guidance). This study demonstrates that 1-Hexadecanamine (C16 amine) is rapidly degraded in various soils and the results indicate that the assumption of low degradation rates for strongly sorbing substances could be unjustified.