I have always used a filter between the pump and the turbine, i've seen a new pump throw off grey matter during break in which reinforced my thought process in this regard.
Interesting gray matter comment. I am gonna chime in with my $0.02 on this one. This is just an FYI from my work experience. (26 years refining and chemicals)
One of the last processes Jet fuel goes through (before going to sales tanks for delivery to the customer) is a clay filtering process. This is basically to help with the purity of the product. Better purity, better price. Simple.
BUT... every now and then these filters fail and contaminate the final product. We say contaminate because basically it drops the purity significantly and causes us to sell it at a much lower rate. It does show up in good filters as a slight grey dust/matter. (micron type of filter of course!)