Abstract: Disclosed is a method for treating in a continuous manner an aqueous solution containing ions of a given type in order to remove these ions from the solution. According to this method, the aqueous solution containing the ions to be removed is first neutralized if it is acidic. Then, it is contacted with a metal salt which is sparingly soluble in water and has a very strong affinity to react with the ions to be removed to form therewith another salt which is insoluble in water, for a period of time sufficient to allow this other salt to be formed and precipitate. This method is very efficient and can be used, by way of example, for removing chromium ions from an industrial waste water, using barium carbonate as sparingly soluble salt.