The noun FILTRATION has 2 senses: 1. the process whereby fluids pass through a filter or a filtering medium. 2. the act of changing a fluid by passing it through a filter. Familiarity information: FILTRATION used as a noun is rare.
A sentence averages eleven words; an A4 / letter size sheet averages 32 to 35 sentences. A normal size sheet of paper with a standard layout, based on 80% - 90% coverage contains about 350 to 400 words.
Four hundred pages is about a hundred thousand words. By the way, the first page of a chapter is estimated to have 250 words, and partial pages other than the first page are estimated to have 125 words. Section breaks (the visual breaks between the scenes in your story) are indicated using a centered number sign (#).