Abstract: The present invention relates to a method for producing a closing layer which improves the water and nutrient retention of soils, particularly of sandy soils, characterized in that a layer of clay mineral/polymer gel capable of binding and releasing water in a reversible manner is introduced into the soil, preferably 20-60 cm below the soil surface, in such a way that a clay mineral is reacted either before or after or during activation in the presence of water, with 0.

Abstract: Contaminated water is contacted with an agent which contains salts or cations of mono-, di-, or trivalent metals in a maximum amount of 50 masspercent and rock granules containing at least 25 masspercent zeolite, preferably clinoptilolite and/or mordenite. The amount of metal salts respectively cations present in the parent zeolitic rock can be increased according to necessity by ion-exchange, adsorption and/or impregnation, i.e. by combination of these processes following eventual dehydration. The agent obtained is homogenized. The exhausted bed can be regenerated biologically or with aqueous solution of a potassium salt.