A wastewater treatment system includes a vertical flow marsh cell that is adapted
to contain media and to support plants having roots extending into the media, the
roots and media positioned to contact water flowing downward through the marsh
cell during a flooding stage, the media and plant roots providing surfaces to which
biofilms can adsorb, the biofilms containing bacteria adapted to adsorb ammonium
ions and nitrify ammonium ions to nitrate during an aerated drained phase. The
marsh cell is configured to receive water from an outlet of a horizontal wetland
that functions essentially anaerobically/anoxically to contain bacteria for transforming
nitrate into nitrogen gas. Water to be treated and water exiting the marsh cell
outlet are transportable to a wetland inlet, providing dilution of incoming wastewater.
Treated water is discharged from the wetland outlet.
