Advances in Water Treatment and Enviromental Management

20 WATER TREATMENTSince 1983, several plants were built using the ion exchange or biological processes (seeTable 2).The biological method still remains the only one that entirely solves the problem by transformingthe nitrates into elementary nitrogen restored to the atmosphere. However, the search for thebest cost ratio for this type of installation has led to propose the ion exchange method as aneconomically attractive alternative for small production rates, despite the ecological problemcreated by the discharge of salty effluents inherent in the process.PESTICIDESTable 2: List of plant using the biological denitrificationor the ion-exchange resins processes in France (non exhaustive list)1—REGULATIONThe word pesticides is a very loose one and gathers under one hat all the chemicals used forthe destruction of organims. These products may be organic or inorganic.As far as organic molecules are concerned, they are of different structures, polarity, size,ionic form, volatility, etc. It therefore seems quite impossible to determine a pesticide index.Analysing the pesticides one by one, appears physically very difficult. In France, for instance,over three hundred active substances are used in agriculture in formulations numbered inthousands.The EEC Directive 80/778 tells us that “by pesticide and related product is meant:– insecticides,– herbicides,