Feed water quality flux rates

Hence, traditional spiral wound NF membranes require the same level of pretreatment as spiral-wound RO membranes, as well as the same flux and flow rate considerations with respect to feed water quality (see Chapters 9.9 and 9.4). 

One can easily infer from Eq. (13.2) that to maintain the same flux rate (7) at a given temperature, one needs to increase dp to reduce AP (NDP), which is related to the feed pressure by Eq. (13.1). Largerporediameters will allow a higher passage of ionic impurities into the permeate water, and as a result one can see a deterioration in the permeate quahty. Designers of UPW systems should pay adequate attention to this issue when selecting the RO membrane modules. Especially, one needs to ensure that the RO permeate quality should be acceptable for the downstream EDI devices in any UPW system. 

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