Reverse osmosis (RO) & nanofiltration (NF)

The standard for producing demineralised water

Reverse osmosis is a powerful membrane technology that removes ions from water. By forcing water under pressure across a semi-permeable membrane, dissolved salts, minerals and organic substances are effectively removed. The result is demineralised water, essential for countless industrial processes.

What is it?

What is reverse osmosis and how does it work?

Reverse osmosis reverses the natural process of osmosis by applying external pressure. This forces water through a membrane that retains virtually all dissolved salts.

Permeate & concentrate

The installation splits the incoming flow into a pure product stream (permeate) and a residual stream (concentrate) in which all salts are concentrated.

Membrane selection

Depending on the source — mains water, rainwater, river water or even heavily loaded process water — we select the optimal membrane type (e.g. for desalination or specifically for demineralised water).

Pressure-driven

Operating pressure ranges from low pressure (for energy-efficient demineralisation) to high pressure (for more heavily loaded streams with a high salt load).

Attention to calcium and magnesium

High concentrations of calcium (Ca) and magnesium (Mg) can lead to scale formation and membrane clogging. That is why proper pretreatment and/or antiscalant dosing is important to keep the installation running efficiently and reliably.

Nanofiltration (NF): the intermediate step in membrane technology

Nanofiltration (NF) can be regarded as a less selective form of reverse osmosis (RO). Whereas RO retains virtually all dissolved salts, NF partially lets certain smaller and monovalent ions pass through.

Crossflow principle

As with RO, nanofiltration works on the crossflow principle, in which the main flow runs along the membrane and only the permeate is forced through it.

Energy-efficient

With an operating pressure of around 5 to 6 bar, NF is often more energy-efficient than a full RO installation when complete deionisation is not required.

Why choose an RO installation from PCA?

An RO installation is often the most cost-efficient and environmentally friendly way to produce high-quality water on a large scale without intensive chemical consumption.

Operational benefits

Desired water quality

Our systems can produce water with very low conductivity. This is crucial for the reliability of your production processes and protects your valuable machinery against limescale and corrosion.

Low maintenance thanks to pretreatment

To protect the membranes, we integrate appropriate pretreatment (softening or antiscalant dosing). This minimises scaling and fouling, so the membranes last for years.

Economic & sustainable gains

Low operating costs

Compared with conventional ion exchange, RO uses virtually no chemicals. Moreover, our installations are fully automated, which keeps operating costs low.

Minimal waste stream

We optimise the configuration for maximum concentrate thickening. This keeps water waste to a minimum and limits your environmental footprint.

Configurations tailored to your needs

No two water requirements are the same. That is why we offer a range of system configuration options.

Single-stage versus two-stage RO

Whereas a single-stage RO is often sufficient, a two-stage system delivers even higher purity by passing the water through a membrane twice. A two-stage RO can also be used to produce less concentrate, as the water is recovered further in a second stage.

Low pressure versus high pressure

We size the system based on the salt load of your influent, from energy-efficient low-pressure systems to robust high-pressure units for complex streams.

Post-treatment for ultrapure water

If extremely low conductivity is required, we install an EDI or mixed-bed ion exchanger downstream of the RO unit.

Protecting your investment

The lifespan and performance of an NF or RO installation depend not only on the quality of the feed water, but also on correct pretreatment, membrane selection and process settings. Depending on the composition of the water, we therefore provide the right protection: ultrafiltration (UF) can be used where suspended solids or an increased biological load are present, while softening or correct antiscalant dosing helps to prevent scaling caused by calcium and magnesium, among others.

In which applications do we use RO/NF?

Reverse osmosis (RO) and nanofiltration (NF) are used when high water quality, desalination or the removal of dissolved substances is required. Depending on the composition of the feed water and the desired permeate quality, we select the appropriate membrane type and tailor the installation for maximum water recovery and operational reliability.

Demineralisation

Removal of dissolved salts to produce low-conductivity process water, for example as feed water for industrial processes.

Water reuse

Upgrading treated waste water so that it can be reused as process, rinse or production water, reducing mains water consumption.

Selective removal with NF

Nanofiltration can be used for the selective removal of hardness ions and larger dissolved components, among others, while certain monovalent salts are partially let through.

Concentrating waste streams

RO and NF can concentrate dissolved substances into a smaller residual stream. This allows more water to be recovered and reduces the volume that needs further treatment or disposal.

FAQ: frequently asked questions about reverse osmosis

Is softening of the feed water always necessary?

To prevent scale deposits (scaling) on the membranes, it is essential that the incoming water is softened or treated with an antiscalant.

What is the service life of the membranes?

With correct pre-treatment and regular cleaning, membranes usually last for several years.

When should I choose nanofiltration instead of reverse osmosis?

Choose NF when you specifically want to remove larger ions, heavy metals or organic contaminants, but where the presence of monovalent salts (such as sodium chloride) in the water is not a problem.

Can you also desalinate seawater?

Yes, we build dedicated high-pressure installations with seawater-resistant membranes for desalination projects.

Experience the difference with PCA Water.

Would you like to know what your reverse osmosis system should look like? Get in touch with us.

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