Nanofiltration System Companies
NF solution providers for selective ion removal, softening, color removal, and high-recovery applications between UF and RO.
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Buyer's guide
The buyer's guide to nanofiltration system
Nanofiltration System Design: Divalent Ion Rejection, Softening Applications, and Operating Parameters
Nanofiltration (NF) membranes have molecular weight cut-off (MWCO) of 200 to 1,000 Daltons and pore sizes of approximately 0.001 to 0.01 microns, positioned between ultrafiltration and reverse osmosis in the membrane spectrum. NF selectively rejects divalent ions (Ca2+, Mg2+, SO42-) at 90 to 98 percent while allowing monovalent ions (Na+, Cl-, K+) to pass at 20 to 50 percent.
This selectivity makes NF ideal for: water softening (hardness removal without full demineralisation, retaining beneficial mineral content for drinking water); natural organic matter (NOM) removal (coloured organic acids, humic substances, MW above 500 Da, 90 to 99 percent rejection); disinfection by-product precursor removal; and selective concentration of divalent salts in industrial streams.
Operating parameters for drinking water NF: feed pressure 3 to 10 bar (vs 15 to 70 bar for RO), water permeability 3 to 8 L per m2 per hr per bar (vs 1 to 3 for RO), recovery 70 to 85 percent from groundwater or surface water with low TDS.
Fouling of NF membranes follows similar mechanisms to RO: organic fouling by NOM requires coagulation pretreatment or periodic alkaline CIP (NaOH pH 11 to 12 plus NaOCl); scaling by divalent salts (CaSO4, CaCO3, BaSO4) requires anti-scalant dosing at 2 to 5 mg per L; biological fouling controlled by biocide dosing and periodic CIP. Lower operating pressure of NF (vs RO) reduces energy consumption by 30 to 60 percent for the same feed water, making NF cost-effective for applications where complete ion removal is not required.
Industrial NF applications: dairy wastewater (concentration of lactose at MW 342 Da, 90 percent rejection, enabling lactose recovery and water reuse); textile dye removal (reactive dyes MW 300 to 1,500 Da, 90 to 99 percent rejection, enabling water reuse and dye recovery); pharmaceutical fermentation broth processing (concentration of small-molecule APIs MW 300 to 1,000 Da); water desalination for domestic supply in areas with moderately brackish groundwater (TDS 500 to 3,000 mg per L) where RO would produce excessively pure, tasteless water.
NF capital cost for a 100 m3 per hr system: $500,000 to $2,000,000. Operating cost: $0.15 to $0.50 per m3. Membrane elements (8-inch by 40-inch NF elements): $300 to $600 each, replacement every 5 to 10 years.
Frequently asked questions
When should nanofiltration be used instead of reverse osmosis?
Choose nanofiltration over RO when: (1) Full desalination is not needed - NF removes hardness and organic matter while retaining sodium and chloride (beneficial for drinking water taste, reduces need for remineralisation post-treatment); (2) Energy cost is a priority - NF operates at 3 to 10 bar vs 15 to 70 bar for RO, saving 30 to 60 percent on energy per m3; (3) Target removal is divalent ions, colour, or organic matter rather than total TDS - NF efficiently removes Ca2+, Mg2+, SO42-, and NOM at 90 to 98 percent while RO is required to remove Na+ and Cl-; (4) Feed water is moderately brackish (TDS 500 to 3,000 mg per L) and target product TDS is 200 to 800 mg per L - NF achieves this without over-treating. Choose RO when: complete TDS reduction to below 100 mg per L is required, PFAS removal is needed, or feedwater is highly saline.
Does nanofiltration remove nitrates?
NF removes nitrates at 40 to 60 percent rejection (monovalent NO3- passes more freely than divalent ions). For drinking water nitrate removal below 11.3 mg per L NO3-N (50 mg per L as NO3, EU DWD limit), NF provides partial removal but may be insufficient for high-nitrate feeds above 100 mg per L. In a two-pass NF system (NF permeate blended or re-filtered), nitrate removal efficiency can be increased to 70 to 85 percent. For complete nitrate removal below EU DWD limits from high-nitrate groundwater, either: (1) RO (95 to 99 percent nitrate rejection), (2) ion exchange with nitrate-selective resin, or (3) biological denitrification (heterotrophic denitrification using methanol or ethanol as carbon source, achieves effluent below 3 mg per L NO3-N) is required. NF plus blending with unaffected source water is a cost-effective approach where alternative lower-nitrate groundwater sources are available.
What pretreatment is needed before nanofiltration?
NF pretreatment requirements are similar to RO but slightly less stringent due to lower operating pressure and less tight membrane. SDI (Silt Density Index) target: below 5 for NF (vs below 3 for SWRO). Pretreatment train for surface water NF: coagulation (alum or ferric at 5 to 15 mg per L, inline without sedimentation for DOC control and membrane protection), multimedia or ultrafiltration (SDI reduction), dechlorination (sodium metabisulphite to below 0.05 mg per L free chlorine - polyamide NF membranes are chlorine-sensitive), cartridge filter (5 micron). For groundwater NF: iron and manganese removal (oxidation plus filtration, iron below 0.05 mg per L before NF to prevent colloidal iron fouling); hardness reduction to reduce scaling propensity (where very high calcium). Anti-scalant dosing for CaSO4, BaSO4, SiO2, and CaCO3 is required at recovery above 70 percent for most ground and surface waters.
What is the typical recovery rate for nanofiltration?
NF systems typically achieve 70 to 85 percent recovery from groundwater (TDS 200 to 2,000 mg per L): concentrate volume is 15 to 30 percent of feed. Surface water NF with low TDS (below 500 mg per L): recovery 80 to 90 percent. At high recovery, the concentration factor (CF = 1 divided by (1 minus R)) amplifies sparingly soluble salts in the concentrate: at 80 percent recovery, CF = 5; at 90 percent, CF = 10. Scaling limits recovery: CaCO3 precipitation above CF 4 to 10 depending on alkalinity; CaSO4 above CF 3 to 8 depending on sulphate; BaSO4 at CF above 2 (very low solubility). Anti-scalant dosing extends these limits. For brackish water with high hardness and alkalinity, softening pretreatment (ion exchange or lime softening) enables recovery above 85 percent without scaling risk.
Illustrative scenario · Small town drinking water supply, East Anglia
A composite drawn from typical projects in this category, not a single client engagement. Figures are indicative.
- Challenge
- A groundwater source serving 8,500 people had TDS of 1,100 mg per L dominated by calcium, magnesium, and sulphate, producing hard, scale-prone water causing consumer complaints. Total hardness was 420 mg per L as CaCO3. Full RO would have produced water requiring remineralisation and was energy-intensive; the utility needed a more cost-effective softening solution.
- Approach
- A two-stage NF system (NF elements, 6-bar operating pressure, 78 percent recovery) was designed to reduce hardness to 80 to 100 mg per L as CaCO3 while retaining sodium and chloride for taste. Concentrate (22 percent of feed) was blended back at 1:3 ratio with bypass raw water to achieve the target blended hardness of 180 mg per L. Anti-scalant dosing at 3 mg per L controlled CaSO4 scaling in the second stage.
- Outcome
- Consumer hardness complaints fell by 91 percent in the first year of operation. Energy consumption was 0.32 kWh per m3, versus 0.85 kWh per m3 modelled for an equivalent RO system. The system achieved DWI approval under WS(WQ)R 2016 within six months of commissioning.
Questions to ask shortlisted providers
5
- 01
What is the feed water composition including TDS, hardness, sulphate, bromide, and NOM concentration?
NF membrane selection and anti-scalant strategy depend on detailed water chemistry; bromide determines bromate risk if ozone is also used, sulphate governs scaling limits.
- 02
What is the target product water quality and is a specific TDS or hardness range required?
NF can be tuned to different softening levels by varying recovery and element selection; the target determines whether blending or two-pass design is needed.
- 03
How will concentrate be managed and what is the consent for disposal?
Concentrate at 15 to 30 percent of feed volume requires an EA permit or trade effluent consent; high-sulphate concentrate from NF is not acceptable for sewer discharge without dilution.
- 04
What CIP protocol is used and what is the warranty period for membrane elements?
NF elements can last 5 to 10 years with correct CIP; element warranty and CIP protocol should be specified contractually.
- 05
Is DWI approval required for the NF membranes and system materials?
Membranes and wetted materials must appear on the DWI List of Approved Products or require individual approval under WS(WQ)R 2016 before operation.
What drives cost in this category
4
- Feed water TDS and required recovery
- Higher TDS and tighter recovery targets increase anti-scalant consumption, CIP frequency, and operating pressure, raising OPEX by 20 to 40 percent.
- System capacity and number of membrane elements
- NF systems scale near-linearly with membrane count; 8-inch by 40-inch NF elements cost 300 to 600 GBP each, and element count drives both capital and replacement OPEX.
- Pretreatment complexity
- Surface water feeds with high SDI require UF pretreatment adding 30 to 50 percent to capital cost; groundwater with high iron or manganese needs oxidation and filtration before NF.
- Concentrate disposal route
- Sewer disposal is cheapest where consent is available; dedicated concentrate management infrastructure (evaporation, deep well) can equal or exceed the NF system capital cost.
Key regulations and standards
4
- Water Supply (Water Quality) Regulations 2016 (WS(WQ)R 2016)
- Require DWI approval for all treatment processes and materials in contact with drinking water; NF membranes and associated chemicals must appear on the DWI List of Approved Products.
- EU Drinking Water Directive 2020/2184 / UK DWD
- Sets parametric values for hardness (no mandatory limit in UK, but 60 to 500 mg per L as CaCO3 is the WHO guideline range), TDS, nitrate, and pesticides that NF is designed to address.
- WRAS BS EN 1717
- Water Regulations Advisory Scheme requirements apply to all water treatment equipment; back-siphonage and contamination prevention must be demonstrated for NF systems connected to mains supply.
- EPR 2016 and EA Trade Effluent Consent
- NF concentrate discharge to surface water requires an Environmental Permit; discharge to sewer requires trade effluent consent under WIA 1991 Section 118; both require TDS and ion concentration limits to be met.
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