A method including the steps of moving fluid through an inlet into a vessel, the vessel being at atmospheric pressure and having at least one side wall and a bottom wall forming an internal chamber within the vessel. The method further includes moving the fluid into and through a filtration unit utilizing a downstream pump, the filtration unit creating a flux of less than or equal to about 0.05 gallons per minute per square foot (GPM/ft2), and moving the fluid processed by the filtration unit to an outlet and out of the vessel.