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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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Description of key information

Based on the available study on biodegradation, di (2-hydroxypropyl) tallow alkylamine is found 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 propoxylates but for two very similar substances di (2-hydroxyethyl) oleylamine  and tri (2-hydroxyethyl) hydrogenated tallow diamine results are available and these results will be used for read-across to primary fatty amine propoxylates (2PO).

A removal percentage of >99.97 is adopted as a worst-case for di (2-hydroxypropyl) tallow amine based on the removal determined in a wastewater simulation test with tri (2-hydroxyethyl) hydrogenated tallow diamine. The adopted removal of di (2-hydroxypropyl) tallow amine through adsorption in a biological treatment plant of 1.63% is based on linear interpolation of the removal percentages of di (2- hydroxyl ethyl) oleyl amine and tri (2-hydroxyethyl) hydrogenated tallow diamine due to sorption when related to the calculated Koc.

No half-life data are available for sediment. The half-life is therefore read-across from hexadecylamine for which a half-life of 16.9 days at 12 °C was observed in soil. Read-across from hexadecylamine to di (2-hydroxypropyl)tallow amine is considered to be justified because both substances are readily biodegradable and have a comparable anticipated sorption to sediment and soil. Because of the possible uncertainty in the sorption behavior of di (2-hydroxypropyl)tallow amine when compared to di (2-hydroxy ethyl)oleyl amine an additional safety factor of 2 is applied to the half-life in sediment.

Key value for chemical safety assessment

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

Additional information

Removal in biological waste water treatment systems

Behavior of organic substances in biological wastewater treatment systems is mainly determined by their biodegradability, capacity to adsorb, and evaporation. SimpleTreat does integrate adsorption, stripping and biodegradation (Struijs et al., 1991, Struijs, 1996). The justness of read-across of removal of organic substances from wastewater in biological treatment systems should therefore be based on these properties. The fate of di (2 -hydroxypropyl) tallow amine in wastewater treatment systems is assessed through read across with di (2-hydroxy ethyl) oleyl amine and tri (2 -hydroxy ethyl) hydrogenated tallow diamine. The removal of di (2-hydroxy ethyl) oleyl amine and tri (2-hydroxy ethyl) hydrogenated tallow diamine have been determined in CAS tests.

The removal of the readily biodegradable di (2-hydroxyl ethyl) oleyl amine (CAS no: 25307-17-9) and tri (2-hydroxy ethyl) hydrogenated tallow diamine(CAS no 90367-25-2) in biological treatment plants was assessed in continuously-fed activated sludge (CAS) unit fed with domestic wastewater spiked with the respective test substances (Akzo Nobel, 2010 and 2011). Di (2-hydroxyl ethyl) oleyl amine and tri (2-hydroxyethyl) hydrogenated tallow diamine were exposed to micro-organisms maintained by addition of domestic wastewater in the CAS test. Both substances were spiked at nominal influent concentrations of 50 mg/L (resp. 37.0 and 28.2 mg/L carbon; calculated) for a period of resp. 48 and 62 days, respectively, and included a control fed with domestic wastewater only.

The mean carbon removal percentage of di (2- hydroxyl ethyl) oleyl amine calculated over 15 measurements of the test was 102± 0.8% (95% confidence interval). These high removal percentages strongly indicate that di (2-hydroxyl ethyl) oleyl amine is biodegraded completely. Formation of water soluble compounds during biological treatment of di (2-hydroxyl ethyl) oleyl amine can be excluded. An accurate assessment of the removal of di (2-hydroxyl ethyl) oleyl amine was established with specific analyses. The mean removal percentage of di (2-hydroxyl ethyl) oleyl amine in the test unit was >99.999% using octadecenyl bis(2-hydroxyethyl) amine as most representative component. These analyses demonstrate that the removal of di (2-hydroxyl ethyl) oleyl amine is complete. Mean removal percentages of octadecenyl bis(2-hydroxyethyl) amine from the influent through adsorption onto sludge assessed in two samples was 0.16% demonstrating that octadecenyl bis(2-hydroxyethyl) amine is primarily removed by biodegradation.

The mean carbon removal percentage of tri (2-hydroxyethyl) hydrogenated tallow diamine calculated over 15 measurements of the test was 99 ± 2% (95% confidence interval). These high removal percentages strongly indicate that tri (2-hydroxyethyl) hydrogenated tallow diamine is biodegraded completely. Formation of water soluble compounds during biological treatment of tri (2-hydroxyethyl) hydrogenated tallow diamine can be excluded. An accurate assessment of the removal of tri (2-hydroxyethyl) hydrogenated tallow diamine was established with specific analyses. The mean removal percentage of tri (2-hydroxyethyl) hydrogenated tallow diamine in the test unit was >99.97.% using tri (2-hydroxyethyl) octadecyl diamine as most representative component. Mean removal percentages of tri (2-hydroxyethyl) hydrogenated tallow diamine from the influent through adsorption onto sludge assessed in two samples was 3.8% demonstrating that tri (2-hydroxyethyl) hydrogenated tallow diamine is primarily removed by biodegradation.

In conclusion, the CAS test demonstrates that both ethoxylated fatty amine derivatives are almost completely removed from the wastewater in conventional biological wastewater treatment plants. These surfactants are primarily removed by biodegradation.

The biodegradability, capacity to adsorb and evaporation of the three alkoxylated fatty amines are given in the Table below. The alkoxylated fatty amine derivatives have been classified as readily biodegradable. The Henry’s Law constants of the surfactants demonstrate that evaporation is negligible. The Log Koc indicates that the potential of di (2-hydroxypropyl) tallow amine to adsorb onto activated sludge is in between of those of di (2- hydroxy ethyl) oleyl amine and tri (2-hydroxy ethyl) hydrogenated tallow diamine.The properties of di (2- hydroxyl ethyl) oleyl amine (CAS no: 25307-17-9), di (2-hydroxypropyl) tallow amine (CAS no: 68951-72-4)and tri (2-hydroxyethyl) hydrogenated tallow diamine(CAS no 90367-25-2) demonstrate that read across is justified.

A removal percentage of >99.97 is adopted as a worst-case for di (2-hydroxypropyl) tallow amine based on the removal determined in a wastewater simulation test with tri (2-hydroxyethyl) hydrogenated tallow diamine. The adopted removal of di (2-hydroxypropyl) tallow amine through adsorption in a biological treatment plant of 1.63% is based on linear interpolation of the removal percentages of di (2- hydroxyl ethyl) oleyl amine and tri (2 -hydroxyethyl) hydrogenated tallow diamine due to sorption when related to the calculated Koc.


 

Table: Biodegradability test results (OECD 301 D), Henry’s law constant and the Log Koc of the ethoxylated fatty amine derivatives and removal percentages of di (2- hydroxy ethyl) oleyl amine and tri (2-hydroxy ethyl) hydrogenated tallow diamine determined in CAS tests (OECD 303). The removal percentages of di (2-hydroxypropyl) tallow amine obtain trough read across are indicated in red.

Substance

Biodegradability

Henry’s Law constant

Pa.m3/mol

(Evaporation potential*)

Log Koc

L/kg

(Potential to adsorb)

Total removal in CAS test

%

Removal via sorption in CAS test

%

Di (2- hydroxy ethyl) oleyl amine

(CAS no: 25307-17-9)

Readily

1.215 * 10 -5(calculated EPI)

 

0.071 (calculated from ratio measured VP/CMC)

 

(Negligible)

Log Koc = 3.70 (calculated, EPI)

 

Log Koc = 4.96 (measured, range 4.61 – 4.97)

>99.999

(measured)

  0.16

(measured)

Di (2-hydroxy propyl) tallow amine (CAS no: 68951-72-4)

Readily

1.885 * 10 -4(calculated EPI)

 

2.2 (calculated from ratio VP/S)

 

(Negligible)

Log Koc = 4.19 (calculated, EPI) Read across from Bis (2 -hydroxyethyl) oleyl amine

>99.97 ( worst-case)

1.63 (interpolation in relation to calculated Koc)

Tri (2-hydroxy ethyl) hydrogenated tallow diamine

(CAS no: 90367-25-2)

Readily

2.878 * 10-10(calculated EPI)

 

 

(Negligible)

Log Koc = 4.91 (calculated, EPI)

Log Koc = 5.81 (measured, range 5.09 – 6.26)

>99.97

(measured)

   3.8

(measured)

*If the Henrys law constant is in the range 10-2< kH < 1 Pam3/ mol, the test substance volatilizes slowly at a rate dependent on the Henrys law constant. If the Henry’s law constant is in the range 1 < kH < 102Pam3/mol, the test substance volatilizes not rapid but possibly significant.

Half-life in sediment

 

No measured half-life data is available for di (2 -hydroxypropyl) tallow aminein soil or sediment. In absence of half-life data in these compartments these can as a worst-case be estimated based on the readily biodegradability and the sorption data as determined in a sorption/desorption test.

As an alternative also read-across from a similar substance may be applied.

For 14C hexadecylamine a half-life in three soils was measured according to an OECD 307 test. Although this C16 amine is strongly sorbing to soil (median Kp soil of 3875 L/kg at lowest measured concentration), half-life’s of 8.14 to 8.98 days were observed at 20 °C. This value can be recalculated (EUSES) to 12 °C a maximum half-life in soil of 16.9 days. As both primary alkyl amines and primary alkyl amine propoxylates (2PO) are readily biodegradable, strongly sorbing and structurally strongly related, it is considered acceptable to use a half-life of 16.9 days in soil and sediment for the primary fatty amine propoxylates risk assessment as well. However because of the absence of real measured sorption data for di (2 -hydroxypropyl)tallow amine an additional precautionary safety factor of 2 is applied on the half-life of 16.9 d to compensate for the possible uncertainty in the sorption leading to a half-life of 33.8 d at 12°C in sediment.