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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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In accordance to Regulation (EC) No. 1907/2006 Annex XI, 1.5, read-across to other structurally related category members was conducted. Read-across data for similar substances, C12-14AS Na (CAS 85886-07-8), C16-18AS Na (CAS 68955-20-4) and C14AS Na (1191-50-0) was used.

The key simulation biodegradation test with C12-14AS Na (CAS 85886-07-8) was conducted according to OECD 303 A by Potoms (1992). It was demonstrated that approximately 100% of the DOC were eliminated using domestic non-adapted activated sludge after 67 days. There was no indication of the presence of any biodegradation residues or non-biodegradable minor components.

One reliable non-GLP simulation test with C16-18AS Na (CAS 68955-20-4) according to OECD 303 A guideline is available (Richterich 2001). Adapted activated sludge from municipal sewage treatment plant was used as inoculum and the initial concentration of the test substance was 20 mg/L as DOC. The inoculum was adapted to synthetic waste water for one week. Biodegradation measured as DOC removal reached 96% after 30 days.

Two supporting studies performed according OECD guideline 314 B and 314 D (Federle 1996a, Federle 1996 b, respectively) are available for C14AS Na (1191-50-0). The OECD 314 B test showed that the removal of C14AS Na (CAS 1191-50-0) was around 98.5% in two activated sludge die-away tests (24 hours). The substance was mineralized (66-69%), incorporated into solids (20-26%), transformed into a metabolite (6-10%), or remained as parent (1.5-2%), after 24 hours. The OECD 314 D test revealed that the substance was completely removed from surface water. After 23 hours 53% was mineralized, 40% was non-extractable (solids), and no substance remained as either parent compound or metabolite. The rate constants for primary biodegradation, ultimate biodegradation, and mineralization in surface water were 3.17, 2.12, and 0.34 h-1, respectively.