Reverse osmosis (RO) membranes, as the core component of water treatment equipment, play an indispensable role in numerous fields due to their efficient, cost-effective, and environmentally friendly characteristics. With the continuous advancement of technology and the emergence of new materials, reverse osmosis technology is progressively addressing various water treatment challenges, providing humanity with safer and more stable water resources. Through in-depth analysis, it becomes evident that the RO membrane holds a pivotal position in the water treatment sector. It not only elevates water quality standards but also drives innovation and progress in water treatment technology as a whole. Driven by the ever-increasing awareness of water resource conservation, the application of reverse osmosis technology will become increasingly widespread, contributing significantly to the sustainable utilization of global water resources.
How to Evaluate the Performance of Reverse Osmosis Membranes? Generally, the performance of reverse osmosis (RO) membranes is measured by three key indicators: recovery rate, water production rate (and flux), and salt rejection rate.
1. Recovery Rate
The recovery rate is a critical indicator of the efficiency of an RO membrane or system. It represents the proportion of feed water converted into product water (purified water). The formula is:Recovery Rate (%) = (Product Water Flow Rate ÷Feed Water Flow Rate) × 100
2. Water Production Rate and Flux
Water Production Rate: Refers to the volume of purified water generated by the RO membrane per unit time under specific pressure conditions. Common units include GPD (gallons per day) and LPH (liters per hour).
Flux: Indicates the volume of water produced per unit area of the membrane per unit time. Units are typically GFD (gallons per square foot per day) or m³/m²·day (cubic meters per square meter per day).
Formula: Water Production Rate = Flux × Effective Membrane Area
3. Salt Rejection Rate
The salt rejection rate reflects the ability of a reverse osmosis (RO) membrane to remove impurities from water. Generally, the removal efficiency of RO membranes for specific contaminants follows these patterns:
Higher rejection rates for polyvalent ions compared to monovalent ions.
The removal rate of complex ions is higher than that of simple ions.
Lower removal efficiency for organic compounds with molecular weights below 100.
Reduced effectiveness against nitrogen-group elements and their compounds.
Additionally, the salt rejection rate is categorized into two types:
Apparent Salt Rejection Rate:
Apparent Rejection Rate (%) = 1-(Product Water Salt Concentration / Feed Water Salt Concentration)
Actual Salt Rejection Rate:
Actual Rejection Rate (%) = 1-2xProduct Water Salt Concentration / (Feed Water Salt Concentration + Concentrate Salt Concentration)] ÷2×A
A: Concentration polarization factor (typically ranging from 1.1 to 1.2).
This metric comprehensively evaluates the membrane’s impurity removal performance under real-world operating conditions.
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Post time: Jun-07-2025