NOVELTY - Use of air or liquid polluted with ammonia, to produce an alkali solution containing ammonia (5-35%) and optionally a solution comprising nitrate salts (10-50%), is claimed.    USE - The air or liquid is useful to produce an alkali solution containing ammonia, where the alkali solution is useful: for the manufacture of fertilizers; for detinning, pickling and descaling metals; for treating ores; for manufacturing dyes; in explosives industry and printed circuit industry; as a solvent for copper; for manufacturing pharmaceuticals, photographic products, food products; in plastics industry; in industrial glues and gelatins; and for preparing ammonium salts or analytical reagents (claimed).    ADVANTAGE - The method: is economic and eco-friendly; treats effluents polluted with ammonia with zero waste; recycles the waste into usable products in the industry; and is simple, safe and avoids fossil fuel consumption for making alkali solutions.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for:    (1) treating an effluent polluted with ammonia, comprising: recovering air or liquid polluted with ammonia; chemically, physically and/or thermally treating the recovered material to cause evaporation of ammonia gas; and absorbing the ammonia gas in a gas-liquid contactor to produce an alkali solution; and    (2) an installation (10) for producing the alkali solution from an effluent gas polluted with ammonia, comprising: a gas-liquid acid contactor (12), comprising a nitric acid washing solution, with inlet (12-1) of gas effluent polluted with ammonia, and an outlet (12-2) of ammonium nitrate solution; a vat (14) for storing ammonium nitrate solution obtained at the outlet (12-2); a vat for storing basic solution; a vat for reaction, with an inlet of ammonium nitrate solution contained in the vat and inlet of base solution contained in the vat, and with an outlet of gaseous ammonia and an outlet of nitrate salts solution; and a gas-liquid contactor, with an inlet of ammonia gas obtained in outlet of the tank and an outlet of alkali solution.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic representation of an installation for treating gaseous effluent.    Installation (10)    Gas-liquid acid contactor (12)    Inlet (12-1)    Outlet (12-2)    Vat. (14)