Blog / Technical guide
When to specify RO or NF for process water
Compare reverse osmosis and nanofiltration against individual ion targets and the project’s concentrate constraints.
HOSON WATER editorial ·
Write product limits for the constituents that matter
List the required conductivity and any separate limits for hardness, chloride, sulfate, silica or other constituents that affect the process. Reverse osmosis is commonly selected for broad salt reduction. Some nanofiltration elements can meet applications focused on hardness or multivalent ions, with rejection varying by ion and membrane. The useful comparison is the modeled product composition at your site conditions.
Use the same water analysis across projections
Provide a representative ion analysis, operating temperature range and expected flow. Ask vendors to use the same feed basis, staging assumptions and product target. Request the predicted product and concentrate composition at each operating case. Review any upstream dosing and whether the concentrate route can accommodate the projected flow and chemistry.
Set a test that checks the end use
If a constituent is critical to performance, include it explicitly in the sampling plan. Conductivity is useful for tracking process trends and should be paired with constituent-specific testing where the application needs it. Specify sample locations and agree on stable operating conditions before comparing results.