Daltonen Focusing on Separating Membrane Products and Fluid Technology Services.
The "Golden Partners" of Reverse Osmosis Membrane Systems: How to Select Membrane Combination Processes
Introduction
In water treatment projects, a single membrane technology often struggles to simultaneously meet both water quality compliance and cost-effective operation. Combining different membrane technologies is becoming standard practice in a growing number of projects.
Drawing on Dalton Membrane’s experience in the design and practical application of multi-membrane combination processes, this article outlines several common membrane combination processes and their applicable scenarios, helping readers quickly build a clear framework for process selection.
Why Combine Membrane Technologies?
Each type of membrane has its own optimal application range: ultrafiltration (UF) excels at intercepting large particles and colloids; reverse osmosis (RO) is highly effective at desalination; nanofiltration (NF) specializes in the selective separation of divalent ions and organic matter.
The essence of process combination is to treat specific pollutants with the matching technology, rather than expecting one membrane to solve all problems. This approach not only protects downstream membranes but also reduces energy and chemical consumption.
Common Membrane Combination Processes
The following three combinations are the most widely adopted routes in engineering practice.
1. Ultrafiltration + Reverse Osmosis (UF+RO)
Serving as pretreatment, UF efficiently removes suspended solids, colloids, bacteria, and viruses. Its permeate typically has a Silt Density Index (SDI) of ≤3 and stable turbidity below 1 NTU, fully satisfying RO feedwater requirements. RO then carries out advanced desalination to deliver consistently stable effluent quality.
This highly mature combination is applicable to scenarios including advanced municipal drinking water treatment, industrial wastewater reuse, and seawater desalination pretreatment.
2. Nanofiltration + Reverse Osmosis (NF+RO)
NF is used for salt separation and pre-concentration: it first separates monovalent salts from divalent salts, reducing the complexity of subsequent concentrate streams. RO further deeply concentrates the NF permeate to complete final desalination or volume reduction.
This combination is commonly used for salt separation and concentration in zero-liquid-discharge (ZLD) processes, as well as high-salinity wastewater treatment, and helps improve resource recovery efficiency.
3. Ultrafiltration + Nanofiltration (UF+NF)
UF removes suspended solids and colloids to protect NF membranes. NF then removes hardness, partial salinity, and organic matter, while retaining some monovalent salts to lower scaling risks.
Applicable scenarios include drinking water softening, partial industrial water treatment, and high-quality domestic water production.
Dalton Membrane Technology (Shenzhen) Co., Ltd. has achieved independent R&D and production of a full range of reverse osmosis, nanofiltration, and ultrafiltration membrane elements. The company can flexibly match different series of membrane elements according to varied water qualities and treatment targets, providing customized membrane combination process solutions.
How to Make the Selection?
When selecting a process, first identify the pollutants to be removed — this determines which membrane technologies to use. Next, check the effluent water quality requirements — these decide membrane precision and the number of combination stages. Finally, assess whether the combination’s complexity is reasonable in light of budget, operating costs, and operation & maintenance (O&M) conditions. The core principle is "adequate, stable, and economical".
Conclusion
The value of membrane combination processes lies neither in stacking as many membranes as possible nor in choosing the most expensive membranes, but in placing each membrane in its most suitable position. Only with the right combination can truly stable water quality, cost-effective operation, and hassle-free maintenance be realized.
If you have questions about membrane combination process selection for your project, Dalton Membrane Technology (Shenzhen) Co., Ltd. can provide selection advice and solution references based on your specific water quality needs and system configurations.
Related News
undefined
