## 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.

You're now able to calculate the key parameters impacting on specific energy consumption in membrane processes specifically. Next we'll look at the immersed membrane bioreactor (iMBR) process.

You can now move to Section 5 The immersed membrane bioreactor process