Pre-filtration for reverse osmosis (RO): small filter, major difference

But it is also a sensitive system. RO membranes are not very resistant. Dirt, biofilm and undissolved particles lead to pressure build-ups, membrane damage and expensive cleaning operations. It often begins with one single error: poor pre-filtration or no pre-filtration at all.

Why pre-filtration is indispensable

Without pre-filtration for an RO system, all kinds of contaminants will land directly on the membrane.  Examples of these contaminants include:

• Floating solids (such as sand, sediment, rust particles)
• Organic fractions (such as proteins or biofilm)
• Oxidising agents such as chlorine

Failing to filter out these contaminants beforehand will result in:

• Blockages
• Greater pressure drop
• Increased load on the high-pressure pump
• Very frequent washing and cleaning
• Shortened membrane element lifespan (a typical lifespan is 4-5 years)

In other words, output falls and the costs per litre of purified water surge.

Choose effective pre-filtration

A well-designed pre-filtration process will eliminate everything that should not end up in the RO system, ranging from coarse particles to fine fractions, and it often also includes an absorption phase.

Depending on the source or process quality, pre-filtration is done using:

• Depth filters (e.g. 10 → 5 → 1 µm) for multi-stage dirt removal
• Activated carbon filter cartridges or modules to eliminate free chlorine, odour and flavour substances
• Absolute filters for maximum certainty in critical processes

We also look at flow, pressure drop and chemical compatibility in selecting the filter. Too much resistance or too little dirt removal is also a risk.

Additionally, our specialists always factor cost-effectiveness, sustainability and operator safety into the advice. It is our mission to recommend the best possible filtration solution to our customer.

Benefits of proper pre-filtration

• Less membrane fouling
• Fewer cleaning and washing cycles
• Lower energy and maintenance costs
• Reliable water quality and longer system service life

BÈTA industrie’s specialists will join your thought process on how to set up your RO pre-filtration

The right filter line is designed based on a water analysis such as an SDI index measurement, consumption data and installation details. Modular, replaceable, and adapted to the existing system. Not a standard solution, but precisely what’s needed.

Owing to our many years of experience with pre-filtration for RO at drinking water companies in the Netherlands and Belgium, as well as at water treatment system manufacturers and end users in the industry, we base our advice not only on figures on paper.

If you want to brainstorm about pre-filtration for an RO system,

schedule an appointment now using the contact form.