Nanofilter converts rivers into drinking water

The world's first and largest nanofiltration plant for treating river water in Paris runs its fully automated process for cleaning the filtration membranes - crucial to the quality of water output

The world's first and largest nanofiltration plant for treating river water north of Paris runs its fully automated process for cleaning the filtration membranes - a process crucial to the quality of the plant's water output - with 30 plastic-lined magnetic drive pumps from Richter.

In the north of Paris, the Syndicate des Eaux d'Ile de France (SEDIF) supplies 39 communities (800,000 inhabitants) from a plant that employs a new and very unique method of treating water from a river source.

Located in Merysur- Oise, the treatment plant needed to increase production capacity.

To do this, SEDIF decided to adopt a technology which had never been used before to treat river water: nanofiltration.

Nanofiltration is a membrane liquid separation technology that is positioned between reverse osmosis (RO) and ultrafiltration.

While RO can remove the smallest of solute molecules, in the range of 0.0001 micron in diameter and smaller, nanofiltration removes molecules in the 0.001 micron range.

As such, nanofiltration is especially suited to treatment of well water or water from many surface supplies like rivers or lakes.

In principle, all pressure-driven membrane filtration processes (microfiltration - ultrafiltration - nanofiltration - reverse osmosis) involve the water being pressed through a membrane by a transmembrane pressure difference.

The membrane then ideally retains all the undesirable water particles.

Which process is used depends on the type and size of the substances to be separated.

The Vivendi decision to go forward with nanofiltration proved to be correct, as the project manager responsible, Arnaud Douveneau notes, "Using nanofiltration, our plant in Merysur- Oise already satisfies the stringent EU demands placed on the quality of drinking water - and that with a much lower volume of chemicals than in conventional plants".

A major factor for the economic success of nanofiltration in water treatment, is the continuous monitoring and cleaning of the membranes.

In Mery-sur-Oise, this takes place in a fully automatic CIP process.

Each membrane is equipped with pressure, flow and conductivity sensors.

The condition of the membrane surfaces is therefore monitored around the clock.

The control takes each of the eight membrane lines out of production every 8 weeks and initiates the cleaning process, which involves acids, bases and detergents.

Dosing out these cleaning chemicals are leak-free, plastic lined magnetic drive pumps from Richter.

Richter specialises in pumps, valves as well as measuring and control equipment for corrosive and pure media.

Douveneau notes that, "Only a few staff work in the fully automated water treatment sector.

The reliability of the pumps must therefore be ensured in the long term".

Douveneau notes that, "We are demonstrating with this plant what the state of the art is today in drinking water technology.

Roughly 800,000 people in the Ile de France region obtain particularly high-quality drinking water - which is also demineralised".

Naturally, such a quality has a price: the plant cost roughly 1 billion French Francs (USD150 million).

But the advantages speak for themselves: people receive drinking water without any taste of chlorine - and a soft water which no longer causes any scaling problems in home plumbing.

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