Conclusions

We can definitely say that the results of the experimentation made by A.M.I. together with the builders of the plant (FRAME S.p.A. of Ozzano Emilia, in the province of Bologna, Italy) are positive.

The data gathered on about 5000 hours of operation of the plant allow us to draw several important conclusions:

• during the last 8 years (the previous experimentation was in 1990), EDR technology for the abatement of nitrates from underground water has met with interesting developments, especially in terms of the performance of the membranes, and this leads us to expect further future developments;

• EDR technology has turned out to be very well focused as an application for treating the removal of nitrates in underground water, especially in terms of preservation of the taste and mineral balance features of the original water;

• EDR technology has absolutely competitive features in terms of management and investment costs when compared to high-tech processes such as Reverse Osmosis. Compared to other technologies also applied in treatment of the removal of nitrates from underground water (Ion Exchange and Biological Denitrification), EDR definitely involves higher investment costs, but still offers an interesting margin of competitiveness in terms of management costs, especially if we consider how much more flexible it is than a biological system (difficulty in controlling the process and critical plant start and stop phases).

• EDR technology, together with Reverse Osmosis (technologies with a higher degree of innovation) certainly present the best features in terms of flexibility and adaptability (at least for the specific application referred to here), especially when we consider that it was already possible during the planning stage to formulate tailor-made solutions, depending on the results which were desired; also, once the plant has been built, it can be easily adapted to new requirements without any special complications in terms of planning and/or management;

• Application of EDR technology for the treatment of underground drinking water presents no special problems in terms of adaptation, since this technology has already been used widely and for a long time in the food industry. Indeed, in the water distribution field conditions are far less critical than in other applications (concentration of the fluid being treated, temperature and pH conditions, etc.), so the life of the main components (membranes and electrodes) is certainly longer. Therefore, the amortisation costs of the plant are less.

References

1 P. Cote: INTERNATIONAL REPORT "State of the art techniques in reverse osmosis, nanofiltration and electrodialysis in drinking-water supply - Anjou Recherche, Centre de Recherche de la Compagnie Generale des Eaux, Chemin de la Digne, BP76, 78603 Maisons Lafitte Cedex, France.

2 American Water Works Association: Manual of water supply practices - Electrodialysis and Electrodialysis Reversal - M38 (1995).

3 G. Gariboldi, S. Moriggi: "Esperienze applicative di trattamento dei nitrati - trattamenti con Osmosi Inversa" - XI Corso Residenziale sull'acqua, CISPEL Lombardia, Milan, May 21st-22nd, 1996.

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