Membrane and Desalination Technologies - TCE Moodle Website

124 L. Song and K.Guan Tay
Average permeate flux (m/s)
9.0×10 –6
8.0×10 –6
7.0×10 –6
6.0×10 –6
increase in driving pressure doubled the duration of the constant average flux with only
marginal increase in the magnitude of the average flux.
4.3. Influence of Feed Water Fouling Potential
With the introduction of the new fouling potential of the feed water and the development of
the mathematical model for fouling development in a long membrane channel, the effect of
membrane fouling on the system performance at different operating scenarios can be quantitatively
predicted. Figure 3.18 shows the fouling development in a long membrane channel
(indicated by the average permeate flux) for feed waters with different fouling potentials.
Operating conditions in Table 3.3 are used in the simulations. The initial average permeate
fluxes are identical for all feed waters since the same clean membrane resistance is used in the
simulations. The period of constant average flux increases with decreasing fouling potential
of the feed water. It is also noted that feed water with higher fouling potential has a larger
decline in average permeate flux with time. This phenomenon is similar to that observed in
fouling tests using laboratory-scale membrane cells.
4.4. Influence of Channel Length
1.38×10 6
1.21×10 6
5.0×10
0 20 40 60 80 100
–6
Time (Day)
Fig. 3.17. The duration of constant average permeate flux greatly affected by driving pressure.
A long membrane channel is commonly adopted in most full-scale RO systems to increase
the permeate recovery. This is achieved by connecting several membrane modules in series in
a pressure vessel. The influence of channel length on the system performance is simulated with
operating parameters in Table 3.3 using feed water with a fouling potential of 10 9 Pa s/m 2 and