Fig. 2 shows the flux reduction in the fouling tests. Values were
calculated dividing the final permeate flux by the initial flux measured
using distilled water. It was observed that Renylat 45 was
the feed stream that caused the highest membrane fouling (the
highest flux decrease for all the membranes), followed by BSA/
CaCl2 solution and finally by BSA solution. As previously reported
by Shi et al. [12], the presence of calcium in the feed solution
increased membrane fouling since this cation can form a bridge
between proteins and membrane, as well as among proteins. In
addition, the heterogeneous composition of Renylat 45, with both
salts and lactose, enhanced membrane fouling