Water cleaning at Holmen's paper mills скачать в хорошем качестве

Water cleaning at Holmen's paper mills

The water that is released from the mills is purified in a three stage process - mechanical, biological and chemical purification. In the mechanical purification, or pre-sedimentation, larger particles are removed. The process water is then passed on to the biological purification and a heavily oxygenated selector basin, a kind of nursery for the bacteria that will break down the pollutants. When needed, a third chemical purification step is used, where flocculation chemicals are added to remove remaining COD, dissolved phosphate or organic material that was not removed in the biological treatment.