United Water Resources' Parent,
Lyonnaise des Eaux
Builds Largest Membrane Filtration Plant
An important newly upgraded full-scale water treatment plant incorporating advanced membrane filtration technology recently went on line at Vigneux-sur-Seine just south of Paris. This French plant built by Suez Lyonnaise des Eaux is now the largest water treatment facility in the world using ultrafiltration as a final polishing step to produce drinking water that exceeds current quality and safety standards.
Designed and operated by Lyonnaise des Eaux, the upgraded and expanded plant can produce over 14.5 million gallons per day (mgd), or 55,000 m3/day, which is distributed to about 200,000 people in the southern suburbs of Paris. The final section of the treatment train employs a membrane process known as Cristal which eliminates any suspended pollutants remaining in the water after the prior process steps, but allows certain desirable mineral salts containing calcium, potassium and sodium to pass through.
Like other modern French water and wastewater plants, not only is the Vigneux-sur-Seine facility technically advanced, it also is architecturally pleasing and spotlessly clean.
The Vigneux-sur-Seine plant, originally built in 1890, uses the River Seine as its raw water source. This water contains a seasonally-variable pollutant load (such as turbidity, algae and organic pesticides) that must be controlled. The facility had been updated several times over the years, including three times in the 1970s. In 1994 an oxidation process using ozone injection in deep tubes (a Lyonnaise des Eaux and its subsidiary company Degremont development) was added to improve the taste of and remove odors from the finished product. Ahead of the ozone step were the conventional sieving, sedimentation and granular activated carbon filtration. Now the Cristal ultrafiltration system has been added to further enhance the quality of the treated water.
Briefly, the process is as follows. Effluent from the
ozonation section has powdered activated carbon (PAC) mixed into
to it (at about 0.8 g/l) and the stream is passed through a 200
micron screen. It then enters the ultrafiltration modules under
pressure to be filtered through pores that are 0.01 microns in
diameter. Vigneux has eight racks with 28 modules, or 224 modules
in all. The role of the PAC particles, which are retained by the
membranes, is to adsorb any remaining organic matter. The
membranes also capture micro-pollutants, many of which can be
bacteria, viruses and pesticides. Consequently the output of the
Cristal equipment is extremely pure water.
[Story provided by Water Online]