What is Nanofiltration and How is it Used in Desalination Processes?

Nanofiltration is an advanced membrane filtration process utilizing semi-permeable membranes. In the high-stakes world of water filtration, an innovative upstart process aims to outperform conventional methods. Introducing nanofiltration — the hot new membrane separation built for speed, precision and efficiency!

You can find more information on our web, so please take a look.

So how does this promising prodigy filter water? It leverages next-gen nanoporous membranes containing holes measured in mere billionths of a meter. When water streams under pressure against this intricate network, only target molecules narrow enough to snake through the constricting labyrinth emerge unscathed. Organics, particulates, salts and unwanted solvents face biological-membrane inspired exclusion.

With system pore architecture finely tuned between reverse osmosis and ultrafiltration extremes, nanofiltration provides elite selectivity. It unravels mineral molecules, humbles heavy metals and softens hardness while permitting more innocuous ions to pass. This lets single-step nanofiltration replace multi-stage treatments.

In recent years, nanofiltration has rapidly gained popularity across industrial and municipal water treatment applications for its abilities to reliably purify water at relatively lower operational costs compared to alternatives.

Nanofiltration — Next-Gen Membranes Channel Purified Flows

Nanofiltration relies on ingenious membrane sieves designed with intricate nanopores to filter water flows down to the billionths of a meter scale. As incoming feed waters rich in contaminants stream against these high-tech barrier layers, it’s almost like an intense molecular showdown at the nano corral!

Only the tiniest of dissolved molecules narrow enough to thread through the membrane’s sub-nanoscopic architecture will be granted passage to the permeate side as purified product water. Larger organic compounds, particulate matter, and troublesome salts face exclusion by the membrane’s carefully controlled gnarled pathways — rejected outright from traversing the nano-maze.

This selective molecular separation leaves behind ultrapure flows fit even for exacting technical processes. And nanofiltration accomplishes it all through clever membrane optimization leveraging intrinsic hydraulic pressure from the feed influx itself.

Common materials used to manufacture nanofiltration membranes include:

• Polyamide thin-film composites
• Cellulose acetate
• Polypiperazine amides

Key properties that define nanofiltration membrane performance include:

• Nanopore diameters ranging from 1–10nm
• Molecular weight cut off (MWCO) from 300– Dalton
• High water flux rate per unit membrane area
• Selectivity towards divalent ions over monovalent salts
• Surface charge determining separation capabilities

Capabilities and Applications of Nanofiltration Processes

The tightly controlled nanopore structures lend nanofiltration technology unique separation abilities from other membrane technologies like MF, UF and RO processes.

Nanofiltration is capable of rejecting:

• Bacteria and viruses
• Proteins
• Sugars
• Dyes
• Pesticides
• Heavy metals like arsenic, lead, chromium
• Water hardness causing divalent salts

It can also partially soften hard water and reduce total dissolved solids present. This makes nanofiltration ideal for:

• Surface water treatment
• Purification of brackish/seawater
• Wastewater recycling
• Food and beverage processing
• Pharmaceutical purification
• Pre-treatment prior to RO desalination

Advantages Over Reverse Osmosis Processes

While reverse osmosis utilizes tighter nanopores for superior separation of monovalent salts, nanofiltration provides significantly lower capital and operating costs. This is due to:

• Lower hydraulic pressure requirements of 70–120 psi compared to 150–300 psi for reverse osmosis
• Higher water recovery and permeate flux rates
• Lower membrane pretreatment needs
• Longer lasting membrane element lifetimes

The ease of use and cost benefits expand possibilities for decentralized and portable nanofiltration units to provide clean, potable water access.

Current and Future Outlook for Nanofiltration Adoption

With worsening freshwater scarcity globally and increased pollution impacting available water resources, nanofiltration is likely to play a big role across municipal and household water treatment applications in the future. Its capabilities spanning surface, brackish and wastewater sources also support usage for agricultural needs.

Advances in nanomaterials, membrane surface modifications and modular system fabrication techniques provide promising pathways to further enhance nanofiltration process performance. This includes improving permeate flux, anti-fouling capabilities and salt rejection rates.

Additionally, integration with renewable energy and automated control systems can augment sustainability and ease decentralized operations in remote areas. Supportive environmental regulations and technology cost reductions will also enable wider nanofiltration adoption going forward.

Nanofiltration has demonstrated immense potential over the last decade through a widening range of industrial and drinking water production applications. As populations expand and climate change worsens water scarcity globally, nanofiltration can reliably amplify usable water supplies from unconventional sources to build resilience.

Ongoing innovation in nanofiltration membrane materials and system engineering will likely support rapid scale-up and provide clean water access to communities worldwide. Hence further development of nanofiltration technology will be crucial for sustainable development.

Demystifying Nanofiltration Membranes: Unraveling What Propels Water Purification and Softening

Nanofiltration through semipermeable membranes leverages selective diffusion principles to filter out contaminants while enabling clean water passage. These nano-scale filtration membranes possess controlled pore diameters in the range of 1–10 nanometers — small enough to separate dissolved microscopic and ionic particles from the water stream. But how exactly do these nanofiltration membranes selectively facilitate transport of water molecules?

Carefully optimizing membrane pore size distributions and charge properties allows the filtration membranes to effectively reject contaminants and treat water to desired quality levels for different purposes like safe potable usage or industrial process needs.

Membrane Structures: Materials Defining Nanofiltration Separation Performance

Early nanofiltration membranes used materials like cellulose acetate polymers. However, these displayed weaker mechanical strengths and undesirable charge properties. Today, thin film composite (TFC) polyamide membranes dominate high-performance nanofiltration offerings.

TFC membranes enhance separation capacity and selectivity power through:

1. Thin dense polymer barrier coating layer scarcely exceeding 500 nm facilitates high flow rates. This nanoporous separating layer gets supported atop heavier porous backing providing additional structural reinforcement
2. Tailored interfacial chains with ionizable amine groups impart a net negative charge throughout the operational pH level range, helping attract cations while repelling anions to augment flux rates and ion selectivity.

Pore Size Distributions: Getting into the Nanoscale Pores Powering Performance

The nanoporous matrix of created nanofiltration membranes possesses a narrow distribution of pores sized from 1–10 nm in diameter. It comprises mostly mesoporous structures from 2–50 nm mixed with some micropores less than 2 nm along the surface layer.

Actual pore sizes are optimized by manufacturers to achieve target salt rejection levels and permeate flux in relation to feed water quality overall. Denser pores reduce total free volume available for water transport, decreasing throughput rates but boosting salinity reduction strengths.

Tuning the nanopore size distribution also minimizes concentrative internal polarisation phenomena that can severely impede water passage over time. These tightly controlled nanoporous matrices enable exceptional ionic and molecular size-based separation power that distinguishes nanofiltration from microfiltration or ultrafiltration processes.

Water Flow through Nanofiltration Membranes

As pressurized water flows through the nanofiltration membrane in either crossflow or dead end mode, the network of nanopores propels selective diffusion across the created osmotic concentration gradient. The net negative charge maintained by the membrane surface also hinders cations from permeating.

Efficient water purification via separation of contaminants occurs through two key rejection phenomenon — steric hindrance and Donnan exclusion.

Steric hindrance filtration occurs when particles or organic molecules exceed the limited physical pore opening sizes, getting physically obstructed from penetrating the pore channels. Donnan exclusion repulsion stems from electrostatic forces due to the fixed negative membrane surface charge interacting with ions carrying opposite positive charge, forcing them to be retained in the retentate zone.

In both cases, contaminant transport gets severely restricted allowing clean water flux passage. Thus nanofiltration leverages diffusion principles and charge controlled ion transport mechanics through nanoscale pores for expelling contaminants with high efficacy.

Harnessing Size Exclusion Principles: How Nanofiltration Leverages Molecular Dimensions for Effective Contaminant Removal

Nanofiltration stands out from other membrane-based filtration technologies due to its precise molecular weight cut-off separation abilities. With pore sizes ranging from 1–10 nanometers, nanofiltration membranes can effectively filter out dissolved particles, organic molecules and salts in the 200– Dalton molecular weight range.

This allows nanofiltration to eliminate contaminants including bacteria, proteins, sugars, dyes, pesticides, and heavy metals — while permitting water and tiny dissolved solids to pass through.

But how exactly does nanofiltration facilitate such selective discrimination based on the size of particles trying to penetrate through the nanoporous membrane layer?

The Fundamentals: Steric Hindrance and Molecular Sieving

The separation process relies on a principle termed “steric hindrance” — where solute molecules or particles exceed the actual physical pore diameter sizes present on the membranes. As they approach the nano-scale membrane pores during the crossflow filtration process, the sheer size limitation physically blocks entry and transport across to the permeate side.

This generates a “molecular sieving” effect by the membrane nanopores, effectively screening entities based on dimensions relative to the created pore structures.

Smaller particles like water molecules, minerals and salts measuring below the 1–10 nm cutoff threshold can easily flow through. While larger molecules get obstructed and retained on the feed retentate side — enabling purified water passage as permeate.

The retailers outwardly convey the nanofiltration membrane’s molecular weight cut off (MWCO) rating to define this separation cutoff threshold explicitly.

But what key particle types can nanofiltration membranes eliminate thanks to such steric hindrance principles leveraging its nanoscale filtering matrix?

Removing Bacteria and Organic Macromolecules Common disease-causing waterborne bacteria like E. Coli, Salmonella, Streptococcus measure 500– nm — clearly excluded from penetrating 1–10 nm nanopores. Similarly, organic macromolecules like proteins (albumin, hemoglobin) possess diameters of 3–20 nm unable to breach nanofiltration membranes.

Sugar molecules also occupy dimensions between 0.5–10 nm hindered through membrane screening. Natural organic matter fractions contributing to disinfection byproduct formation also carry sufficient molecular weight to enable removal.

Heavy Metals and Inorganic Ions

Dissolved heavy metal salts and inorganic cation/anions represent smaller targets compared to microorganisms — but still exceed nanofiltration membrane pore sizes.

Scale-inducing divalent ions like calcium, magnesium and sulfate present as ionic radii complexes spanning 0.9 to 1.14 nm — thereby blocked via steric effects. Other problematic heavy metals like chromium, arsenic and lead also occur as larger hydrated ionic forms hindered by size constraints.

However, the smaller atomic size of sodium (0.97Å) and chloride (1.67Å) means partial nanofiltration membrane passage. Though electrostatic charge interactions assist further selectivity.

Achieving Ultrapure Water Quality

Pharmaceutical applications demand ultraclean water, with nanofiltration complementing reverse osmosis and ion exchange polishing stages. The combination elicits over 99% impurity reduction — by leveraging size exclusion phenomenon at the nano-scale to deliver pure permeate water quality.

The precisely controlled 1–10 nm scale nanopores in nanofiltration membranes enable unprecedented selectivity in filtering dissolved salts, organics and particulates from feed water. This harnesses fundamental steric hindrance principles that force larger contaminating entities to be retained — while allowing clean water transport. Further fine-tuning membrane surface charge and hydrophilicity aids the separation performance.

Exploiting Size Matters Principles: Nanofiltration’s Nano-Precision in Screening Contaminants for Water Purification

When dealing with filtration, size does matter. For nanofiltration, size exclusion lies at the heart of its unmatched separation potential across filter technologies. With nanopores sized in the 1–10 nanometer range, nanofiltration membranes leverage molecular size constraints at a precision scale unmatched by alternative membrane filtration forms.

This facilitates effective elimination of dissolved particles and salts as tiny as 0.5 nanometers using steric hindrance phenomenon. The upshot? Exceptional selectivity in trapping diverse contaminants while permitting water permeation.

But what is it about the controlled nano-dimensions that empower such discrimination ability during the transport process?

Nanofiltration Separation Dynamics: Surface Interactions at Microscopic Levels

As the pre-pressurized feed water approaches the membrane surface, its dissolved components interact at the nanofiltration boundary layer through charge effects and restricted mobility.

The nanoporous matrix acts akin molecular sieves — screening components based on size cutoffs. Particles with larger relative molecular weights like organics, sugars and heavy metals exceed pathways dimensions. Their transport halts at the membrane exterior unable enter the pores.

However, the smaller hydrated diameter of water molecules, sodium and chloride ions allows partial equilibrium penetration into internal pore channels aided through diffusion.

It is this precise fine-tuning of pore diameters in the 1–10 nm levels that elicit a steric selectivity effect. Enabling nanofiltration exceptional control over filtering targets compared to conventional and loose microfiltration membranes.

Benchmarking Nanofiltration Separation Efficacy

But what metrics define efficacy of nanofiltration membranes? Parameters like molecular weight cut offs, rejection ratios and flux recovery help gauge process efficiency.

Tighter nanostructures with lower MWCOs near 300 Da can achieve over 90% dye and sugar elimination. While Da membranes reduce divalent salts, pesticides and acids at lower pressures. High rejections indicate reliable retention of dissolved contaminants.

Normalized flux rates quantify flow per membrane area. Values spanning 10–30 LMH/bar for seawater signify steady transports with minimal fouling concerns.

Nanofiltration thus demonstrate multi-fold higher throughputs than hyper-selective reverse osmosis membranes. This expands utility for moderate separations.

Applications: Industries Leveraging Nanofiltration’s Size-Based Potential

The capacity to discriminate based on subtle molecular weight and diameter variations find wide applications:

• Food/Beverage: Eliminate dyes, sugars, oils, preservatives
• Pharma: Concentrate thermally sensitive antibiotics by retaining proteins, endotoxins
• Textiles: Remove traces dyes complements, surfactants through appearance of dye in permeate
• Automotive: Extract paint solids reaching paint booth wastewater streams
• Semiconductors: Purify ultrapure water post-reverse osmosis for washing circuits

In each sector, nanofiltration facilitates further polishing and fractionation needs unachievable through conventional membranes.

Future Outlook

Advances in nanofiltration membrane fabrication using nanomaterial coatings, surface modifications and functionalization will elevate separation efficiency and expand applications across chemical, textile, food/beverage and energy industries through .

In particular, enabling organic solvent and extreme pH compatibility coupled with fouling resistance will widen usage scenarios. Supported integration with renewable energy and real-time monitoring will also boost sustainability credentials.

Nanofiltration vs Reverse Osmosis: Key Differentiators and Advantages of NF Membrane Systems

Reverse osmosis and nanofiltration rank among the most widespread pressure-driven membrane separation technologies across industrial and drinking water production applications. Both leverage semipermeable membranes to filter out dissolved salts, organics, proteins and particulates from feed water streams.

But nanofiltration offers unique advantages over reverse osmosis processes — making it an attractive technology for customized separation needs:

Lower Operating Pressures Nanofiltration membranes possess slightly larger pores than reverse osmosis ones — ranging from 1–10 nanometers versus the smaller 0.1–1 nm reverse osmosis filters. This enables nanofiltration systems to effectively operate at lower applied hydraulic pressures of 70–120 psi.

In contrast, reverse osmosis units require 150–300 psi to achieve desired deionization through the tighter nanopores. The high pressure demands substantial pumping energy. Nanofiltration’s lower pressure requirements thus save operating costs.

Higher Water Recovery and Permeate Flux Rates

The lower hydraulic pressure specifications also facilitate higher recovery rates — producing more purified water. Typical nanofiltration systems can achieve 70–85% recoveries from feed water volume, while standard reverse osmosis hovers at 50–60% conversion efficiency.

Likewise, permeate flux production measuring flow per membrane surface area reaches 25–30 LMH for nanofiltration. Reverse osmosis flux rates range 5–15 LMH in comparison due to the intense pressures compacting passageways. This further boosts process throughput.

Lower Fouling Tendencies

Tighter reverse osmosis membrane structures suffer more frequent fouling and mineral scaling issues that severely impede water transports. Nanofiltration’s slightly larger pores and operating conditions mitigate such fouling.

This lowers costs associated with membrane cleaning while retaining steady flux production over longer operational lifetimes before requiring element changeouts.

Customized Separation Selectivity

Nanofiltration leverages a tighter pore structure than ultrafiltration for removing viruses, proteins and macromolecules. Yet it is more size-selective than fully retentive reverse osmosis membranes.

This allows precise calibration of membranes with narrower or relaxed molecular weight cutoffs — enabling customized filtration of target contaminants based on application needs.

Reliable Water Softening and Organics Removal

The selective separation capabilities of nanofiltration also facilitate excellent hardness ion removal. This reliably softens water by eliminating scale-inducing divalent cations like calcium and magnesium.

ShekeSaisi are exported all over the world and different industries with quality first. Our belief is to provide our customers with more and better high value-added products. Let's create a better future together.

Simultaneously, nanofiltration membranes retain trihalomethanes precursors and natural organic matter — helping curb dangerous disinfection byproduct formation during downstream processing. Reverse osmosis does not offer such flexible selectivity.

Nanofiltration technology benefits from lower operating costs, higher recoveries, increased membrane life cycles and tunable separation cutoffs compared to full desalination reverse osmosis processes. This expands utility for moderate separations.

Ongoing advances in nanofiltration membrane fabrication and modular system design are poised to accelerate adoption across myriad industries from food and pharmaceuticals to metals production and semiconductors manufacturing.

Leveraging Nanofiltration Synergies for Optimized Reverse Osmosis Desalination Performance

With worsening freshwater scarcity globally, reverse osmosis (RO) technology plays a pivotal role in reliable production of potable water from seawater and brackish sources. However, the intense pressures and tightly packed membrane structures make RO units susceptible to frequent fouling while incurring major energy demands.

This is where nanofiltration (NF) technology offers synergistic advantages as upstream pretreatment before reverse osmosis desalination stages.

NF Softening Mitigates RO Scaling and Fouling

The slightly larger nanopores in NF membranes compared to RO provide customized selectivity. This permits elimination of divalent hardness ions like calcium and magnesium during softening — while allowing some monovalent salts passage.

Such selective separation prevents problematic scaling and fouling compounds from accumulating on downstream RO units. This is crucial given RO’s more intense operating conditions exacerbate precipitation and clogging issues that severely impede transport efficacy over time.

The NF softening pretreatment substantially reduces cleaning chemical usage for remediating such issues. This further lowers operating expenditures.

Stepwise Separation Boosts Recovery Rates

Leveraging NF as the initial separation stage also boosts overall system recovery upstream. Being less selectivity means each NF membrane element extracts relatively more purified water compared to standalone RO units.

This decreases the feed volume loading on the downstream RO process. Since less contaminant concentration minimizes osmotic back pressures, the RO membranes can now operate at optimal fluxes — improving online availability.

Such strategic multi-stage design raises production quantities from the initial feedwater intake — enhancing productivity metrics.

Lower Energy Requirements and Carbon Footprint

The NF system’s lowered hydraulic pressure specifications, alongside softened water minimizing RO polarization limits, collectively reduce net energy utilization by the process train.

This further diminishes the overall plant’s greenhouse gas emissions associated with power sourcing. Hence, appropriately integrating NF synergies cuts operational expenditures and environmental impacts.

Future Outlook for Compact Integrated NF-RO Systems

Ongoing advances in membrane module engineering using nanomaterials and functionalizations will elevate selectivity and throughput rates for next-generation NF offerings.

These will drive widespread adoption within compact, automated NF-RO process trains. Incorporation of renewable energy sources and remote performance analytics through the cloud also paint an innovative picture.

One where smart, modular NF-RO schemes reliably expand affordable access to clean drinking water sustainably.

Benefits of nanofiltration:

• Lower operating costs than reverse osmosis
• Higher water recovery rates (70–85%)
• Longer lasting membrane life
• Reduced fouling and scaling
• Customizable separation capabilities
• Reliable water softening
• High organic contaminant removal

Types of contaminants removed:

• Bacteria and viruses
• Sugars and dyes
• Pesticides and herbicides
• Natural organic matter
• Multivalent heavy metal ions
• Calcium and magnesium ions
• Organic pollutants and solutes

Industries using nanofiltration:

• Food and beverage
• Pharmaceutical and biotech
• Semiconductor manufacturing
• Textiles production
• Automotive industry
• Landfill leachate treatment
• Power generation systems
• Municipal water utilities

Nanofiltration membrane materials:

• Thin film composite polyamides
• Cellulose acetate
• Polypiperazine amides
• Carbon nanotube composites
• Graphene oxide membranes
• Ceramic membranes
• Hybrid organic-inorganic membranes

Pretreatment methods before NF:

• Screening and microfiltration
• Cartridge filtration
• Coagulation/flocculation
• Adsorption processes
• pH adjustment
• Chlorination
• Dechlorination

Future nanofiltration improvements:

• Fouling resistant coatings
• High selectivity membranes
• Nanomaterials-enhanced fluxes
• Organic solvent and extreme pH compatibility
• Automated self-cleaning modules
• Sensors for real-time monitoring
• Renewable energy integration
• Lower module costs

Frequently asked questions

What is nanofiltration and how does it work?

So what exactly is nanofiltration? Essentially, it uses specialized membranes with nanopores between 1–10 nanometers wide to filter out contaminants and particles from water. We’re talking pores over 100 times thinner than a human hair!

Imagine those membranes are super selective bouncers guarding the doors to an exclusive water purification club. As contaminated water pushes against the membranes, only the smallest and most desired water molecules get the VIP pass through those nanoscopic doorways. Dissolved salts, organic chemicals, minerals, bacteria and other Party Crashers all get rejected and bounce backs. The perfect flavor, phase and purity make it through!

It’s not quite as harsh as reverse osmosis which uses insane pressure at even smaller pore sizes to remove even more contaminants. But it generates far better water quality than ultrafiltration which uses way bigger pores that allow undesirables to slip by.

Nanofiltration operates at the “goldilocks” scale — just the right amount of pressure and membrane tune-ability letting designers target removal of specific water contaminants. Whether crafting the perfect cup of coffee or safely recycling industrial wastewater, nanofiltration leverages nanotechnology to actively purify almost any water source!

How is nanofiltration different from reverse osmosis and ultrafiltration?

Unlike overly aggressive reverse osmosis or lax ultrafiltration bouncers, nanofiltration membranes keep just the right restrictions at the molecular door to optimize water filtration.

While reverse osmosis uses crazy high pressures and micro-pores removing salts and minerals, nanofiltration artfully targets middle contaminants — rejecting pesticides, dyes, sugars and flexible organics up to 500 Daltons with lower energy demands. And compared to ultrafiltration’s gaping 20–100nm pores that scarcely filter lighter solutes, nanofiltration refuses biologically-harmful divalent metals, bacteria and viruses.

Optimally-tuned between these extremes, nanofiltration flexibly forms a personalized purification playlist — removing contaminants deemed undesirable depending on the industrial application while permitting other trace ions’ passage.

What types of contaminants can nanofiltration remove?

Nanofiltration membranes may seem nonthreatening as tiny sheets filled with imperceptible pores. But when contaminants try trespassing from water sources? These bouncers flex their finely-tuned capabilities!

With pore sizes craftily covering 1–10 nanometers, nanofiltration blocks anything above 300–500 Dalton molecular weights — rejecting pesticides, pharmaceutical residues, dyes, sugars, detergents, and other emerging trace organics.

And unlike lax ultrafiltration, nanofiltration membranes prohibit passage for insidious invisible contaminants too — eliminating bacteria, viruses, protozoa, and parasites through size exclusion. Those disease-causing agents can’t slip their sly submicron shapes through such well-guarded portals!

In addition, the membranes bare an intrinsic negative charge. This repels troublesome positively-charged metal ions like calcium, magnesium, iron, and heavy metals, refusing them entry and alleviating scale-inducing hardness.

What industries use nanofiltration technologies?

With capabilities spanning water softening to pathogen removal, nanofiltration gets recruited by high-profile industries seeking specialized purification:

Sensitive pharmaceutical manufacturing depends on nanofiltration to concoct ultrapure compounds, while equally persnickety electronics firms trust nano shields to filter corrosive solutions and polish wastewater for reuse.

Seeking taste and profit margins exceeding purity itself, stalwarts across food and beverage, alcohol and sugars rigorously refine products through tailored nanofiltration.

Demanding textile dyeing and finishing processes leverage nanofiltration both pre-use for incoming water treatment and post-use for recycling wastewater streams after weaving their chromatic magic.

Oil and gas also mitigate high salinity extracted waters, as well as membrane-protected desalination for hydraulic fracturing fluid formulations through nanofiltration’s selective separation strengths.

What are the advantages of nanofiltration over other processes?

Compared to reverse osmosis, nanofiltration systems have significantly lower pumping requirements and capital costs. NF membranes also have higher water fluxes, higher water recovery, lower energy consumption and longer membrane life with reduced fouling tendencies. Compared to ultrafiltration, NF provides higher contaminant removal abilities. And unlike conventional filtration, NF offers non-destructive, selective molecular separations. These factors make it very cost-effective.

What is the typical rejection and recovery rate for nanofiltration processes?

Industry nanofiltration membranes can achieve 50–80% salt rejection for low to moderate salinity feeds. Rejection proportionally improves with increasing divalent salt contents. Water recovery rates typically range from 70–85% depending on water quality, system configuration and proper operational parameters. These outperform comparably sized reverse osmosis systems.

How is nanofiltration pretreatment useful for reverse osmosis units?

Nanofiltration pretreatment can help prevent scale formation from water hardness compounds and other foulants in reverse osmosis units. This is done by selectively removing the scaling species like calcium and magnesium upstream. NF softening also reduces entrained organics that can chemically degrade membranes over time or clog pores. The overall lower contaminant loading preserves RO element performance, enhancing operational efficiency.

What materials are used to make nanofiltration membranes?

Most modern nanofiltration membranes utilize thin-film composite (TFC) polyamide synthetics as the active separation layer coated over polysulfone or polypropylene backing support. TFC polyamides offer excellent mechanical durability, chemical resistance, and permeate flux rates critical for membrane filtration performance. New generation membranes also leverage nanomaterials like carbon nanotubes for advanced separations.

What is the future outlook for nanofiltration adoption globally?

Nanofiltration adoption for water treatment applications is expected to grow at over 12% CAGR over the next decade. Key supporting factors are worsening industrial wastewater pollution and freshwater scarcity necessitating recycling. Advances in lower fouling membrane materials, portable/decentralized systems, integration of automation and IoT monitoring will also accelerate nanofiltration installations across industrial and municipal water infrastructure.

How can nanofiltration support global sustainable clean water access?

By enabling unmatched, energy-efficient selectivity for eliminating diverse contaminants, nanofiltration technology can help tackle the pressing challenge of water insecurity facing communities worldwide. Deploying modular, intelligent NF-based water purification infrastructure leveraging advances in nanomaterials will support clean water accessibility targets while minimizing environmental impacts through responsibly managed water reuse, recycling and desalination.

Reverse osmosis and nanofiltration are often spoken about in unison as they are similar membrane technologies that solve a variety of process separation and filtration needs. The two technologies are being utilized more and more by industrial facilities looking to recycle and treat industrial wastewater for reuse and conservation. As water scarcity issues continue to increase, these technologies have become a long-term economical solution for avoiding astronomical discharge and water-usage fees in addition to serving other filtration requirements, such as process-water generation and product concentration.

If you are looking for a separation and/or filtration solution, you might be thinking RO/NF is a good fit. But what are reverse osmosis and nanofiltration, exactly, and how do they work?

This article will simplify these technological processes so you can get a better understanding of how they might be able to help your facility:

Reverse osmosis, also known as RO, is a membrane technology that uses a semipermeable medium to remove certain ions and particles from a liquid stream. RO removes contaminants based on their particle size and charge—generally anything that is 0. µm or larger, including:

• bacteria
• calcium
• colloidal particles
• fluoride
• iron
• manganese
• organic material
• pyrogens
• salt
• viruses

Because of its filtration properties, RO is often used to:

• clean wastewater to acceptable effluent standards or for reuse
• concentrate solvents used in the food and beverage industry, such as whey
• create ultrapure process water streams, such as required in the microelectronics industry
• desalinate seawater or other brine solutions
• generate potable drinking water

RO is also the reverse process of osmosis, a phenomenon that occurs naturally when a lower-solute stream (with a higher-water concentration) migrates toward a higher-solute stream (with a lower-water concentration) through a semipermeable membrane to achieve concentrate equilibrium.

[Download our free RO/NF membrane system e-book.]

While RO and NF are both membrane technologies that uses a semipermeable medium to remove certain ions and particles from a liquid stream, they can be distinguished based on the size of particulates that each is able to remove. Comparatively, RO and NF are capable of removing finer contaminants than microfiltration and ultrafiltration, with applications including the removal of:

• hardness
• heavy metals
• nitrates
• organic macromolecules
• radionuclides
• sulfates
• total dissolved solids (TDS)

Nanofiltration, however, delivers slightly coarser filtration than RO, with the ability to remove particles as small as 0.002 to 0.005 μm in diameter, including pesticide compounds and organic macromolecules, while retaining minerals that RO would otherwise remove. Nanofiltration membranes are capable of removing larger divalent ions such as calcium sulfate, while allowing smaller monovalent ions such as sodium chloride to pass through.

Because of its filtration properties, nanofiltration is often used to:

• concentrate and demineralize valuable byproducts, such as metals from wastewater
• generate potable drinking water
• remove nitrates
• remove pesticides from ground or surface water
• soften water

As mentioned above, RO is the reverse of osmosis, which is a passive, naturally occurring process that happens without the use of energy. For example, if you were to place a semipermeable membrane in a tub of water then add salt to one side, the water would naturally migrate from the side without salt to the side of the semipermeable membrane where you added the salt to dilute the concentrated, salt-contaminated liquid until the two sides were equally dilute. You would end up with one side having a higher level of water, creating what is known as osmotic pressure. RO and NF function similarly, the difference being what size particulates are being filtered out.

With RO/NF, since you are removing contaminants from a high-solute liquid stream, energy larger than the naturally occurring osmotic pressure must be applied to force the solvent from the (highly concentrated solution) through the semipermeable membrane in the opposite direction than what would occur naturally and without force. This causes the permeate to pass through the semipermeable membrane while trapping and filtering out any contaminates larger than the pure water that passes through to the lower-pressure side.

The pressure required to push the solvent through the semipermeable membrane depends on the concentrate of solids. The more concentrated the stream is, the more pressure you need to apply to overcome the osmotic pressure and force the permeate (filtered water) through. This leaves you with a highly concentrated reject stream that is either used or discarded, depending on the separation/concentration needs of the facility.

SAMCO has over 40 years’ experience custom-designing and manufacturing RO/NF systems for a range of industries and solutions, so please feel free to reach out to us with your questions.

For more information or to get in touch, contact us here to set up a consultation with an engineer or request a quote. We can walk you through the steps for developing the proper solution and realistic cost for your RO/NF treatment system needs.

Head on over to our blog to learn more about industrial filtration and process separation technology. Some articles that might be of specific interest to you include:

• Does Your Facility Need a Reverse Osmosis or Nanofiltration System?
• How Do You Choose the Best Reverse Osmosis and Nanofiltration Membrane System for an Industrial Facility?
• Reverse Osmosis and Nanofiltration Membrane Filtration Systems: Common Problems and How to Fix Them
• What Are the Best Companies for Reverse Osmosis and Nanofiltration Membrane Systems?
• Reverse Osmosis vs Nanofiltration Membrane Process: What Is the Difference?