A self-contained filtration assembly with a self-contained filtration cassette therein. The cassette may be formed from one or more layers membranes and spacers (spacers, screens, or combinations thereof) all having the same general shape. The cassette may have a feed inlet path and a retentate outlet path extending through the layers of the cassette within the perimeter of the cassette, and a permeate outlet path between the cassette exterior and the interior of the cassette housing. The housing may have a generally circular or elliptical cross-section. A clamping assembly may hold together the components of the housing, and may be elongated in a direction along the flow path of the feedstream through the cassette. Various port-defining zones defined in the layers of the cassette may be sealed in a manner facilitating assembly of the cassette as well as isolation of the flow paths therein.

A filter structure includes a housing having an inlet and an outlet; a first filter embedded in the housing and including a polymer membrane for filtering a first fluid flowing from the inlet into the housing; and a second filter embedded in the housing, filtering a second fluid filtered by the first filter, and including mesoporous silica nanoparticles (MSN).