Flux Definition

Flux indicates the productivity of membrane and defined as equation (1). Table 1 summarizes the three different units commonly used.

image002        ————————– (1)

                                                                   Symbol Three different units commonly used
 image004 Flux LMH gfd m/d
 image006 Permeate volume L gal m3
 image008 Membrane area m2 ft2 m2
 image010 Time duration hr day day

The above units can be inter-converted using the following conversion factors.

1.00 gfd  = 1.70 LMH
1.00 gfd  = 0.041 m/d
1.00 m/d = 41.7 LMH
1.00 m/d = 24.5 gfd
1.00 LMH = 0.59 gfd
1.00 LMH = 0.024 m/d

Concentration factor (CF)

Concentration factor of membrane process is defined as the ratio of feed water volume over concentrate volume and calculated as equation (2). This is an important operating parameter in crossflow tubular membrane and reverse osmosis (RO). But this concept is not used in MBR with immersed membranes.

image012    ————————– (2)


Princi12= feed water volume (m3)
Princi16= permeate volume (m3)
Princi14= feed flow rate (m3/hr)
Princi17= permeate flow rate (m3/hr)


Recovery is a derivative variable from CF and indicates the efficiency of fresh water use in RO. It is calculated as equation (3).

image014————————– (3)

where Princi18is permeate volume (m3). All the volumetric parameters can be substituted with corresponding flow rate parameters.