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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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The continuous activated sludge (CAS) test was performed according to ISO Guidelines, and in compliance with the OECD principles of Good Laboratory Practice. Amides, C18-unsatd., N-[3-(dimethylamine)propyl] were exposed to micro-organisms maintained by addition of domestic wastewater in the CAS test. The substance was spiked at a nominal influent concentration of 50 mg/L (36.5 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 Amides, C18-unsatd., N-[3-(dimethylamine)propyl] calculated over 14 measurements obtained from day 35 to 48 of the test was 105 +/-1% (95% confidence interval). These high removal percentages strongly indicate that the substance is biodegraded ultimately. Formation of water-soluble compounds during biological treatment of Amides, C18-unsatd., N-[3-(dimethylamine)propyl] can be excluded.

An accurate assessment of the removal of Amides, C18-unsatd., N-[3-(dimethylamine)propyl] was established with specific analyses. The method (LC-MS/ MS) for the determinati on of substance was satisfactory with regard to the linearity, repeatability of the injections, limit of quantification (LOQ), recovery and specificity. The mean removal percentage of substance in the test unit was assessed with the specific analysis from day 44 to 48 was >99.997% using octadecenamide-N- [3-(dimethylamino)propyl] as representative component. These analyses demonstrate that the removal of Amides, C18-unsatd., N-[3-(dimethylamine)propyl] is almost complete. Concentrations in the sludge of the reactor sampled on days 47 and 48 were 341 and 24 µg/L. Mean removal percentages of test substance from the influent through adsorption onto sludge assessed in two samples was therefore <0.02% demonstrating that the substance is primarily removed by biodegradation. In conclusion, the CAS test demonstrates that the substance is almost completely removed from the wastewater in conventional biological wastewater treatment plants. Amides, C18-unsatd., N-[3-(dimethylamine)propyl] is primarily removed by biodegradation.