a second washing step 8 whereby the liquid phase 9 washed out and free of the liquid can be re used as washing water in the process this liquid phase 9 will also contain the originally added chelating agent because it is not bound by the pulp but follows along with the liquid the partial flow 6 of the pulp which now contains bound metal ions is directed to a third washing step 10 before washing the ph is lowered to below about 3 and preferably to about 2 5 which can be brought about by the addition of sulfuric acid the main part of the metal ions is hereby again released from the pulp and washed out in the form of metal containing waste water 11 which can be treated separately or be emitted to the recipient this waste water corresponds to from about 1 to 2 m 3 per ton of pulp based upon the total amount of the main flow of pulp a special advantage from an environmental point of view is that the waste water 11 does not contain any chelating agent because this material follows along with the liquid phase 9 the main flow 1 of pulp is bleached with hydrogen peroxide or ozone in the bleaching step 5 after such bleaching the pulp is washed in a washing step 12 whereafter the partial flow 6 of pulp free of metal ions is reunited with the main flow 1 the liquid phase 9 free of metal ions can be used as washing.