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The distribution in a sewage treatment plant (STP) has been estimated using the SimpleTreat model (implemented in EUSES 2.1.2), see table below.

Table: Distribution modelling for STP



Fraction of emission directed to air by STP



Fraction of emission directed to water by STP



Fraction of emission directed to sludge by STP



Fraction of the emission degraded in STP



The constituents of phenyl silsesquioxanes are not expected to undergo any significant biodegradation, and are predicted to have high Henry’s Law constants and high log Kow/log Koc. Distribution modelling for STP indicates that sludge is the main compartment to which they are expected to partition in a sewage treatment plant, with partition to water and air also being significant. Sediment and soil are likely to be the main compartments to which phenyl silsesquioxanes will partition in the wider environment.