Registration Dossier

Environmental fate & pathways

Biodegradation in water: screening tests

Currently viewing:

Administrative data

Link to relevant study record(s)

Description of key information

Key value for chemical safety assessment

Additional information

In the test on ready biodegradability (OECD 301D, Solvay 1993), sodium perborate degraded by ca. 85% after 48 hours incubation. Degradation was determined by a colometric method measuring the decrease of active oxygen. However, slower degradation was found compared to the studies of Guhl (2000), where half-lifes in the range of minutes were observed. An explanation for the slower degradation is - besides the lower inoculum density - possibly the pretreatment of the sludge (aerating before start of incubation). By this procedure microbial activity of the inoculum is expected to be significantly reduced due to shortage of substrate. As no additional substrate was added after diluting the sludge in aqueous mineral solution and starting of incubation, no recovery of the microbial activity (degradation potential) was possible which may have led to the reduced degradation of sodium perborate compared to the test of Guhl (2000).

In laboratory tests Guhl (2000) found rapid removal of 1 -25 mg/L sodium perborate (measured as H2O2) by domestic activated sludge (DT50 = 0.5 - 1.3 minutes) and also by domestic raw waste water (DT50 = 1 - 8.5 minutes), which was taken from the grit chamber of a STP. Besides the removal of sodium perborate also the degradation behaviour of hydrogen peroxide as initial test substance was determined in the study. Half-lives for this compound in activated sludge (DT50 = 0.5 - 1 minutes) as well as in domestic waste water (DT50 = 0.5 - 8.2 minutes) were exactly in the range of perborate. This fact supports the conclusion that the degradation of the perborate to peroxide may have happened within a few seconds.