L'alimentation en eau des zones industrielles de Port-Jérome et du Havre

¹ Ingénieur des Ponts et Chaussées Secrétaire Général du Comité Technique de l'Eau de Haute-Normandie
² Ingénieur des Ponts et Chaussées, Chef de l'Arrondissement du Havre

Résumé

Two refineries, owned by Esso-Standard and Mobil Oil, were built by the Seine at Port-Jérôme in 1932-33. Thirty-odd years later, in 1958 and 1962, about half a dozen allied industries set up alongside and the industrial water supply problem had to be reviewed. There were three possible sources : (i) ground-water ; (ii) the River Commerce with 1.25 cubic metres per second average flow into the Seine ; (iii) the upper reaches of the Seine estuary where the water contains a variable amount of sea salt (depending on tidal phase and the discharge of the river itself). In 1961, the Seine-Maritime River and Bridge Department, comparing requirements and resources, showed that the inadequacy of useful surface water and deterioration in quality of ground water would be a hindrance not only for building new factories but also for developing-or even maintaining-the existing ones. The only reasonable means of increasing supply, it was concluded, was to make use of Seine water. Before settling on the Seine-water draw-off point, measurements lasting more than a year were started in 1962 between Quillebeuf and Villequier. These showed that there would only be a few days per year when low Seine flows would combine with unfavourable tidal coefficients to give high salinities. Measurements on suspended matter showed that the water intake should be set as close to the surface as possible but that it would nevertheless be necessary, in order to obtain industrial-quality water, to remove the greater part of the suspended solids. To select the most efficient and economical treatment process, water treatment firms were asked in 1964 to submit tenders for installing at Villequier a pilot plant to pump and treat Seine water. Tender finally selected came from the Degrémont Company, who proposed : (i) prechlorination of raw water to 0.5-1 ppm in order to disperse algae as suspended matter ; (ii) flocculation with aluminium sulphate and active silica followed by a Pulsator-type settling basin ; (iii) rapid sand filter; (iv) sterilisation by chlorination. The plant includes : (i) Seine water intake ; (ii) treatment plant (two 50,000 cubic-metres-per-day units ; (iii) pumping equipment and piping up to a storage basin; (iv) storage reservoir (50,000 cubic metres for the first stage); (v) distribution piping. Water costing, designed as an incentive to industrialists to keep their water consumption as steady as possible, runs on a dual basis : Subscription based on a given flow of water ; II. - Costs based on water actually used. Price per unit volume covers the cost of water treatment. The project sprung from the difficulties encountered by factories in obtaining suitable water. Local resources seemed to be exhausted, thus holding back industrial development. To avoid pumping too much water from the aquifer, it was decided to satisfy industrial needs with treated Seine water. Today, the choice made seems especially good since industry in the Havre lower down the river is a large potential consumer (250,000 cubic metres per day forecast for 1985) and resources on the right bank of the Seine are limited. This means that potable water will have to be brought at considerable expense from far-off Yport or even the Fécamp district. Provided the quality (especially the chemical characteristics) of treated Seine water does not deteriorate, this source should well satisfy the future needs of industry.