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Advanced Membrane Fouling Characterization 113
Permeate flux (ms –1 )
1.2×10 –5
1.1×10 –5
1.0×10 –5
9.0×10 –6
8.0×10
0 100 200 300 400 500
–6
Time (min)
Fig. 3.5. Decline of permeate flux with time in fouling experiments with different colloidal concentrations
of 25 mg/L ( filled square), 50 mg/L ( filled circle), 100 mg/L ( filled triangle), 150 mg/L ( filled
inverted triangle), and 200 mg/L ( filled diamond ). Driving pressure = 1.5 10 6 Pa, salt concentration
= 1,000 mg/L NaCl, and feed crossflow velocity = 0.15 m/s.
Table 3.2
Properties of the
fitted lines at
different colloidal
concentrations
Colloidal
concentration
(mg/L)
25 1.55 10 10
50 3.19 10 10
100 5.99 10 10
150 8.22 10 10
200 1.11 10 9
Gradient Initial flux (m/s) kf (Pa s/m 2 )
9.84 10 6
9.83 10 6
1.01 10 5
9.69 10 6
1.01 10 5
3.97 10 9
8.32 10 9
1.47 10 10
2.33 10 10
2.87 10 10
synthetic feed water with different colloidal concentrations, determined from the lines best
fitted to the flux data shown in Fig. 3.5.
Table 3.2 shows that the fouling potential of the synthetic water increases with colloidal
concentration. This phenomenon is reasonable because more colloidal particles are brought
onto membrane surface at higher particle concentration. The fouling potentials are plotted
against colloidal concentrations and shown in Fig. 3.6. The graph shows that all the data
points can be well fitted with a straight line. The strong linear relationship between fouling
potential and colloidal concentration indicates that fouling potential is an excellent indicator
of the amount of foulants in the feed water.