## 4 Membrane process parameters

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Video 4 outlines the definitions of flux, pressure, permeability, membrane aeration, recovery and rejection.

Video 4 Membrane process operating parametersVideo player: 4a%20Membrane%20process%20parameters.mp4

The equations for flux, pressure, permeability, SADm, SADp, recovery, rejection and concentration factor are as follows:

 Flux, L/(m2h) or LMH J = Q/A Permeability, LMH/bar K = J/TMP Recovery, R Qp/Qf Rejection, r Cp/Cf Concentration factor, CF 1/(1+R), when r = 100% Specific aeration demand for membrane air scouring, Nm3/m2 membrane area, SADm Qa/A Specific aeration demand for membrane air scouring, Nm3/m3 permeate, Q'a,m SADm/J', J' in units of m3/(m2h)

where

TMP is the transmembrane pressure in bars, 1 bar = 100,000 Pa

Cp and Qp are the permeate flow and concentration

Qf and Cf are the feed flow and concentration

Qa is the air scour rate in Nm3/hr, Nm3 = 'normal cubic metres', 'normal' being standard temperature and pressure taken as 20°C and 1 atmosphere pressure (~1 bar).

Question 7:

Using the above equations, calculate the flux, in both LMH and SI units, for a permeate flow of 150 m3/hr through 200 membrane modules each having an area of 30 m2.

Question 8:

If the permeability is 80 LMH/bar, what is the TMP?

Question 9:

If the feed flow is 43 L/s, what is the recovery?

Question 10:

Calculate the specific aeration demand in

(i) Nm3/h per m2 membrane area, and
(ii) Nm3 per m3 permeate, if air is delivered to these 200 modules at a rate of 2400 Nm3/h.

SADm = Aeration rate/area = 2400/(200 x 30) = 0.40 Nm3/h per m2.