There are in Colombia waters with certain amount of selenium, toxic for human and animáis. There waters are influenced by Solls of Villeta Formatlon type. The amaunts of selenium are very hlgh. A procedure was developped ¡n order to reduce the selenium ¡n the water, uslng a mlx of ferrlc chlorlde and ferrous sulphate. With thls procedure it was possible, to reduce the dissolved selenium below 0.01 ppm, whlch is non toxic for human and animal health. Two procedures for deter-mlnatlon of mlcroamaunts of selenium were standarlzed.
