Because the long DNA filaments in a chromosomal DNA prep aggregate
into a cloud of fibers when ethanol is added, there's an easy way to
quickly get rid of most contaminants.
Don't collect the DNA by centrifugation, as the pellet will contain
all contaminants that are also insoluble in ethanol. Instead collect
the DNA the traditional way, by 'spooling' it onto a glass pipette as
it comes out of solution, or by simply swirling the ethanol mixture
until the precipitating DNA fibers form a non-viscous clump and then
fishing the clump out with a pasteur pipette or clean forceps.
This method only works for chromosomal DNA, because plasmids and RNA