After fermentation, the brew will contain a large number of solids and suspended material such as wort (malted barley residue), yeast cells, fats and proteins that can form a sediment at the bottom of the fermentation vessel. In this state, beer appears hazy and will deteriorate if left untreated, so must undergo multiple filtration processes.
The first of this is a coarse filtration stage, ensuring the removal of larger particulates, advancing to a smaller micron rated particle filter. Then advancing to a smaller micron particle filter. This allows the large volumes to be filtered quickly and aid the achievement of a clearer, polished beer.