Filtration removes water from the concentrate. Removing water from the concentrate is important so that water does not have to be transported with the concentrate, increasing transportation costs. In Finland, water is also removed to prevent the concentrate from freezing during transport. Some of the removed water can also be recycled back into the process.

There are two filters on display: a disk filter and a rotary drum filter. In addition to this, the most common filter in use in concentration plants today is the pressure filter. The disk filter and the rotary drum filter operate on the same principle, namely by sucking the concentrate sludge through a filter cloth. The pressure filter works by pushing water out of the concentrate sludge through a fabric and heat-drying it.