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Membranes
RO flux and recovery
Recovery, concentrate flow, average flux and concentration factor of a reverse osmosis system.
Recovery—%
Average flux—L/m²·h
Concentrate flow—m³/h
Concentrate / feed concentration—×
Formula
Y = Qp / Qf Qc = Qf − Qp J = Qp / (N × S) Cc / Cf = [1 − Y(1 − R)] / (1 − Y)
Sources
- DuPont FilmTec Reverse Osmosis Membranes Technical Manual, Form No. 45-D01504-en, Rev. 8 (September 2021)
Recovery and permeate flux definitions, Table 27 Eq. 51 for the concentrate-to-feed concentration ratio. - FilmTec, Design Equations and Parameters, Form No. 609-02057-604 (The Dow Chemical Company)
Earlier edition of the same equations (Eq. 14).
Limits and assumptions
- Flux is averaged over the whole system. Lead elements run at higher flux than tail elements.
- The concentration ratio uses one average rejection value. It does not include concentration polarization at the membrane surface.
- Allowed flux depends on the feed water source and the membrane. Check the design limits in the manufacturer guidelines. They are not built into this calculator.
- The example values are for illustration only. Take the active area from the element datasheet.