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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. Due to the very rapid hydrolysis of tert-butyl(chloro)dimethylsilane, the distribution calculation is done for the silanol hydrolysis product, tert-butyl(dimethyl)silanol.

Table: Distribution modelling for STP

Fraction of emission directed to water by STP



Fraction of emission directed to air by STP



Fraction of emission directed to sludge by STP



Fraction of the emission degraded in STP



tert-Butyl(chloro)dimethylsilane hydrolyses very rapidly to form tert-butyl(dimethyl)silanol and hydrochloric acid. Ready biodegradation is not relevant for hydrochloric acid being inorganic. tert-Butyl(dimethyl)silanol is not expected to undergo any significant biodegradation and is predicted to have low Henry’s Law constant and low log Kow/log Koc. Distribution modelling for STP indicates that water is the main compartment to which it is expected to partition in a sewage treatment plant. Water is also likely to be the main compartment to which tert-butyl(dimethyl)silanol will partition in the wider environment.