Membrane Flux Rate Calculator
Calculate the permeate flux for Reverse Osmosis (RO), Ultrafiltration (UF), and Nanofiltration (NF) systems.
Calculated Flux Rate:
What is Membrane Flux Rate?
In water treatment and membrane technology, Membrane Flux represents the volume of fluid (permeate) that passes through a unit area of membrane surface over a specific period. It is the primary indicator of how efficiently a membrane system is operating.
Understanding flux is critical for engineers because it directly relates to the fouling rate. Operating at a flux rate that is too high can lead to rapid membrane scaling or organic fouling, requiring more frequent chemical cleanings (CIP) and reducing the lifespan of the membrane elements.
The Membrane Flux Formula
The standard calculation for flux (J) is expressed as:
Where:
- J: Flux (usually in LMH or GFD)
- Q: Permeate Flow Rate (Volume/Time)
- A: Active Membrane Surface Area
Common Units of Measurement
Depending on the region and industry, two main units are used:
- LMH: Liters per Square Meter per Hour (Standard Metric unit).
- GFD: Gallons per Square Foot per Day (Standard US Imperial unit).
To convert from GFD to LMH, multiply the GFD value by 1.699.
Typical Flux Rate Ranges
Different water sources require different flux rates to prevent fouling:
| Source Water | Typical Flux (GFD) | Typical Flux (LMH) |
|---|---|---|
| RO Seawater | 8 – 12 | 13.5 – 20.5 |
| RO Brackish Well Water | 14 – 18 | 24 – 30.5 |
| RO Surface Water | 10 – 14 | 17 – 24 |
Practical Example
Imagine an industrial RO system with 5 membrane elements. Each element has an active area of 40 m² (Total Area = 200 m²). If the system produces 3,000 Liters per hour of permeate:
- Flow Rate (Q) = 3,000 L/h
- Total Area (A) = 200 m²
- Flux (J) = 3,000 / 200 = 15 LMH