Method for purifying waste water comprising the following steps: - a preliminary step designed to determine an amount of zeolitite necessary to abate an amount of ammonium NH4+ in wastewater to a pre-determined concentration value (C e target), wherein an adsorption isotherm is determined which describes a balance condition between retention and release of NH4+ from a surface of a solid phase, the adsorption isotherm being determined experimentally through a series of tests in which different masses of zeolitite are added to a constant volume of wastewater; - a first step of adsorption of NH4+ through the use of zeolitite which comprises: a first sub-step of addition to wastewater of the amount of zeolitite determined in the preliminary step, and of mixing the wastewater through mixing means in oder to keep the zeolitite in suspension, a second sub-step of separating a solid fraction from a liquid fraction, - a second step of precipitating struvite which comprises: a first sub-step of checking the concentration of NH4+ in wastewater treated with zeolitite, a second sub-step of computing the amount of reagents to be added to wastewater, depending on the amount of NH4+ detected in the first sub-step, necessary to arrive to a concentration in wastewater with a molar ratio of 1.0:1.5:1.0 (Mg:NH4:PO4), a third sub-step of simultaneous addition to wastewater of the following reagents previously dissolved in water: anhydrous dibasic potassium phosphate K2HPO4 and hepta-hydrate magnesium sulphate MgSO4·7H2O, a fourth sub-step of addition to wastewater of a solution of potassium hydroxide KOH to buffer the pH to 9, a fifth sub-step of separation of the struvite, precipitated after the addition of reagents to wastewater. - a preliminary step designed to determine an amount of zeolitite necessary to abate an amount of ammonium NH4+ in wastewater to a pre-determined concentration value (C e target), wherein an adsorption isotherm is determined which describes a balance condition between retention and release of NH4+ from a surface of a solid phase, the adsorption isotherm being determined experimentally through a series of tests in which different masses of zeolitite are added to a constant volume of wastewater; - a first step of adsorption of NH4+ through the use of zeolitite which comprises: a first sub-step of addition to wastewater of the amount of zeolitite determined in the preliminary step, and of mixing the wastewater through mixing means in oder to keep the zeolitite in suspension, a second sub-step of separating a solid fraction from a liquid fraction, a first sub-step of addition to wastewater of the amount of zeolitite determined in the preliminary step, and of mixing the wastewater through mixing means in oder to keep the zeolitite in suspension, a second sub-step of separating a solid fraction from a liquid fraction, - a second step of precipitating struvite which comprises: a first sub-step of checking the concentration of NH4+ in wastewater treated with zeolitite, a second sub-step of computing the amount of reagents to be added to wastewater, depending on the amount of NH4+ detected in the first sub-step, necessary to arrive to a concentration in wastewater with a molar ratio of 1.0:1.5:1.0 (Mg:NH4:PO4), a third sub-step of simultaneous addition to wastewater of the following reagents previously dissolved in water: anhydrous dibasic potassium phosphate K2HPO4 and hepta-hydrate magnesium sulphate MgSO4·7H2O, a fourth sub-step of addition to wastewater of a solution of potassium hydroxide KOH to buffer the pH to 9, a fifth sub-step of separation of the struvite, precipitated after the addition of reagents to wastewater. a first sub-step of checking the concentration of NH4+ in wastewater treated with zeolitite, a second sub-step of computing the amount of reagents to be added to wastewater, depending on the amount of NH4+ detected in the first sub-step, necessary to arrive to a concentration in wastewater with a molar ratio of 1.0:1.5:1.0 (Mg:NH4:PO4), a third sub-step of simultaneous addition to wastewater of the following reagents previously dissolved in water: anhydrous dibasic potassium phosphate K2HPO4 and hepta-hydrate magnesium sulphate MgSO4·7H2O, a fourth sub-step of addition to wastewater of a solution of potassium hydroxide KOH to buffer the pH to 9, a fifth sub-step of separation of the struvite, precipitated after the addition of reagents to wastewater.