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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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Description of key information

Half live in sediment determined from TGD default values for  readily degradable substances and with calculated Kpsed. 
Simulation test performed in continuously fed activated sludge (CAS) unit

Key value for chemical safety assessment

Additional information

Biodegradation in sediment

The Kpsed was determined as 50000 L/kg. The suggested half-life for a readily degradable substance with a Kpsed in the range >10000 - <=100000 L/kg is 30000 days for the sediment layer. This value is considered as extremely conservative but in the absence of measured data will be used in the exposure assessment as a worst-case. The half-life of the bioavailable fraction of alkyl dipropylene triamines in the water phase of sediments is expected to be in the order of a few days, which is based on experiments with dialkyldimethylammonium salts (van Ginkel et al, 2003).

Biological wastewater treatment

The removal oleyl polypropylene polyamine consisting of 36% of dipropylene triamine and 43% of tripropylene tetramine in biological treatment plants was simulated in a continuously-fed activated sludge (CAS) unit fed with domestic wastewater spiked witholeyl polypropylene polyamines(Akzo Nobel, 2009b). A control unit fed with only domestic wastewater was included in the study.The incubation temperature of both CAS units ranged from 19 to 21°C. The pH of the effluent of the CAS units varied from 6.0 to 7.4. The CAS test was started with sludge from a plant treating domestic wastewater and maintained by the daily addition of primary settled sewage. The hydraulic retention time and the sludge retention time were 6 hours and 10 days, respectively. The dry weight in the CAS units ranged from 2.7 to 3.5 g/L. The hydraulic retention time was set at 6 hours.

The immediate high removal percentages observed are attributed to adsorption and may be some biodegradation. The removal remained high throughout the study. The mean removal percentage of oleyl polypropylene polyamines-carbon calculated over 15 measurements obtained from day 44 to 60 of the test was 88±5% (95% confidence interval). The high removal percentage over a period of more than 8 weeks indicates that oleyl polypropylene polyamines includingoleyl dipropylene triamine arebiodegraded ultimately. Formation of water soluble compounds during biological treatment ofoleyl dipropylene triaminecan be excluded.

Removal ofoleyl dipropylene triaminein the test unit was assessed with the LC-MS method from day 56 to day 63. A mean removal of 99.9% was determined with octadecyl dipropylenetriamine as representative component. These analyses demonstrate that the removal from the aqueous phase is almost complete. The meanoleyl dipropylene triamineconcentration in the sludge of the test unit sampled on days 59 and 60 was 115 mg/L also determined with octadecyl dipropylene triamine as representative component. The calculated mean removal percentage of oleyl dipropylene triamine from the influent through adsorption onto sludge was 5.8 demonstrating that oleyl dipropylene triamineis primarily removed by biodegradation.In conclusion, the CAS test demonstrates that oleyl dipropylene triamine will be biodegraded almost completely in a conventional biological wastewater treatment plant.