The target liquid is fed into the filtration vessel under pressure via a nozzle on the side of the vessel, and passes through the cartridge element to its core. Large particles of foreign matter are excluded from entry into the filter element, and settle at the bottom of the vessel. Fine particles entering the element become entrapped in its microfilament network, and are filtered out. In this way, foreign matter is removed from the fluid, and the clean filtrate is collected via the outlet in the base of the vessel. The pressure at the inlet of the filter cartridge rises as it entraps foreign particle matters and then in time, the pressure at the inlet reaches differential pressure (difference of pressure at the inlet and outlet).