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Biodegradation in water and sediment: simulation tests

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The results of a CAS test (OECD 303A, GLP, reliability 1) demonstrate that the test substance is removed by 99.99% from the waste water in conventional biological waste water treatment plants. Chemical analysis of the test substance confirmed that removal occurred for 99.8% via biodegradation and for 0.2% via sorption to sludge. The mean organic carbon removal percentage of sodium capryliminodipropionate was 95±4%.

In accordance with column 2 (9.2.1.2) of REACH (Regulation 1907/2006/EC) Annex IX, simulation testing on biodegradation in water and sediment is not needed as the substance is readily biodegradable.

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Discussion

The continuous activated sludge (CAS) test was performed according to ISO Guidelines, and in compliance with the OECD principles of Good LaboratoryPractice. Sodium capryliminodipropionate was exposed to micro-organisms maintained by addition of domestic wastewater in the CAS test. Sodium capryliminodipropionate was spiked at a nominal active ingredient influent concentration of 45.2 mg/L (25.7 mg/L carbon; calculated) for a period of 63 days and included a control fed with domestic wastewater only.

The mean organic carbon removal percentage of sodium capryliminodipropionate calculated over 13 measurements obtained from day 43 to 63 of the test was 95±4% (95% confidence interval). The results demonstrate that the continuous activated sludge system treating domestic wastewater spiked with sodium capryliminodipropionate removes 95 % of the organic carbon of the test substance.

An accurate assessment of the removal of sodium capryliminodipropionate was established with specific chemical analyses. The method (LC-MS/MS) for the quantification of the test substance was satisfactory with regard to the linearity, repeatability of the injections, limit of quantification (LOQ), recovery, and specificity. The mean removal percentage of sodium capryliminodipropionate in the test unit as quantified with the specific analysis from day 59 to 63 was 99.99%. These analyses demonstrate that the removal of sodium capryliminodipropionate from the wastewater is complete. Sodium capryliminodipropionate concentrations in the sludge of the reactor sampled on days 62 and 63 were 3.7 and 3.1 mg/L. The mean removal percentage of sodium capryliminodipropionate from the influent through adsorption onto sludge assessed is therefore 0.2%.This means that 99.8% removal of sodium capryliminodipropionatein the CAS test unit is achieved by biodegradation. In conclusion, the CAS test demonstrates that sodium capryliminodipropionate, is completely removed from the wastewater in conventional biological wastewater treatment plants with biodegradation as the primary removal mechanism.

In accordance with column 2 (9.2.1.2) of REACH (Regulation 1907/2006/EC) Annex IX, simulation testing on biodegradation in water and sediment is not needed as the substance is readily biodegradable.

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