Abstract: A low-cost water and wastewater treatment system having several embodiments achieves efficient contaminant removal in an environmentally "friendly" manner. The technology couples biological and passive chemical unit processes, and relies largely on pH changes to remove contaminants. A first embodiment focuses on a sequential two-unit treatment process consisting of a submersed aquatic vegetation (SAV) cell followed by a limerock (LR) bed. A second embodiment merges the two sequential treatments into one compartment where the LR bed is coincident with the SAV unit. A third embodiment describes the replacement of the SAV unit with a periphyton raceway unit, which is then followed sequentially by a LR bed. All three embodiments contain control elements for determining when and how much recycle within and flow between the treatment systems should occur, and if and when chemical addition should be performed.