Abstract: Apparatus, methods and media for filtering liquids are especially suited for insertion into an existing storm water catch basin. The filtration that occurs reduces concentration of storn water runoff pollutants including heavy metals, suspended solids, particles and oil and grease. While being able to handle the high flow rates of storm water runoff, the filters also remove small particles and oil and grease the filters are arranged such that overflow from uppermost filters, as they become clogged, is directed by overflow weirs to change direction to allow filtration by lower filters. Storm water surges during peak intensity are permitted to over flow directly into a catch basin to prevent ponding. The invention can also be used above ground to treat pumped liquid from industrial and environmental sources.