In general, the present invention is directed to systems for treating water or wastewater. In accordance with some embodiments of the present invention, the system may utilize a vessel with a plurality of filter beds, at least one inlet, and at least one outlet, and the system may include: a first filtration bed comprising a first granular and/or angular media, the first media having a high surface area and configured for biological and physical treatment of the water or wastewater; a second filtration bed including a second granular and/or angular media, the second media having a lower surface area than the first media; wherein the water or wastewater enters the vessel via the at least one inlet, flows through the first filtration bed and the second filtration bed, and exits the vessel through the at least one outlet.