TX Subsurface flow constructed wetlands typically use emergent aquatic plants that are grown in beds of porous media.
Effluents flow through the bed and remain below the surface of the media.
Pollutants are removed by microbes and plant roots that are attached to the media, and by precipitation and adsorption. More data is needed on proper hydraulic designs for subsurface flow systems. The hydraulic properties of beds must be known to prevent problems with surface runoff, incomplete treatment, odors, mosquitoes and vectors. The growth of plant roots and the maturation of beds need to be considered. Constructed wetlands are inexpensive and the use of shredded tires makes them more economical by reducing the cost of the filter bed.