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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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A waste water treatment simulation test was performed with Amines, N-C16-18-alkyl (evennumbered) propane-1,3-diamine (133779-11-0). 99.4% removal was observed using specific chemical analyses (LCMS/MS) of the effluent during day 56 to 60 (n=5). Besides to that the sorption to sludge was measured and this accounted for 4.1% of the total removal which means that 95.3% is removed by biodegradation. Based on the readily biodegradability of all diamines (C10-18) and the fact that the simulation test has been performed with the diamine with the lowest bioavailability, it is considered justified to use the same results for the other more bioavailable diamines as for these a higher total removal and lower removal via sorption are anticipated.

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The removal of Amines, N-C16-18-alkyl (evennumbered) propane-1,3-diamine was simulated in a continuous activated sludge (CAS) unit (Akzo Nobel, 2008b + 2008c; Dr U. Noack Laboratoriën, 2008). One unit was fed with domestic wastewater spiked with 50 mg/L of Amines, N-C16-18-alkyl (evennumbered) propane-1,3-diamine, the control unit was fed with domestic wastewater only. The aeration vessel had a capacity of 0.36 L, the flow rate was 1.1 L/day (i.e. the hydrolic retention time was 6 hours). The sludge concentration ranged from 2.4 to 3.1 g dw/L, The sludge retention time was 10 days. The units were maintained at 20 to 22°C. The test units were preconditioned for one week after which sludge wasting was started. After introduction of the test substance at day 0, removal of Amines, N-C16-18-alkyl (evennumbered) propane-1,3-diamine was monitored by non purgeable organic carbon (NPOC) analyses. Amines, N-C16-18-alkyl (evennumbered) propane-1,3-diamine was readily adsorbed by the sludge particles which lead to an immediate removal of approximately 100%.

During the last week of the test, 5 LC/MS measurements of the test substance were conducted and 99.4% removal of Amines, N-C16-18-alkyl (evennumbered) propane-1,3-diamine was observed. The removal determined in CAS tests is equal to the sum of degradation and adsorption onto sludge.

To assess the contribution of each removal process the removal due to sorption was quantified by taking test samples from the sludge on two days during the last week and subjecting them to chemical analysis. Al specific chemical analyses were performed using methods developed and validated according to SANCO/3029/99 rev.4 (11/07/00). Based on these measurements it is concluded than only 4.1% (3.4 – 4.7) of Amines, N-C16-18-alkyl (evennumbered) propane-1,3-diamine is removed by adsorption onto the sludge. The results demonstrate that Amines, N-C16-18-alkyl (evennumbered) propane-1,3-diamine is primarily removed by biodegradation (mineralization). In conclusion, the CAS test demonstrates that Amines, N-C16-18-alkyl (evennumbered) propane-1,3-diamine will be biodegraded almost completely in a conventional biological wastewater treatment plant.

These results as observed for Amines, N-C16-18-alkyl (evennumbered) propane-1,3-diamine

can in general be considered to represent the worst-case removal for diamines (C10 -18) in an STP. Shorter alkyl chain diamines will have a similar or higher removal than compared to the C16 -18 -alkyl (evennumbered) because of the higher bioavailability for biodegradation. Shorter alkyl chain diamines will be removed to a lower extend via sorption. It is therefore considered justified to use the results as observed for a

mines, N-C16-18-alkyl (evennumbered) propane-1,3-diamine also for other members of the diamines category.