As mentioned, water permeability was measured before and
after every use (filtration or cleaning process). This has allowed
us to determine the loss of permeability due to fouling during
the must filtration and the recovery after the cleaning process.
Results are presented in Table 4. The water permeability obtained
is within the range given by the manufacturers. It can be noticed
that after nanofiltration of white must, water permeability was
reduced by 35% and there is a slight recovery after the cleaning process, without reaching the original value of the brand
new membrane (there is a final reduction of 20% over the original permeability). After filtration of red must, the permeability
loss is almost negligible when compared with the permeability of
departure and there is no recovery after the subsequent cleaning
process.