ABSTRACT
Recent studies in Florida demonstrated that shallow ponds containing large leaved floating macrophytes, such as pennywort (Hydrocotyle umbellata) and water hyacinth (Eichhornia crassipes), can remove biochemical oxygen demand (BOD5 ) from domestic wastewaters at high rates. Gravel-bed systems (GBS) consist of gravel-filled trenches planted with one or more species of emergent macrophytes. Wastewater is usually passed through GBS in a subsurface flow to eliminate problems associated with surface ponding (mosquito production, odors). This chapter examines BOD5 and suspended solids (SS) removal rates from primary effluent using floating and emergent macrophytes cultured in pond and gravel-bed systems. Although floating aquatic macrophyte-based treatment systems have been shown to provide secondary treatment of domestic effluent for several years without operational problems, questions remain regarding the long-term performance of GBS. To facilitate design and operation of GBS, effects of wastewater loading rate, plant species, and harvest regime on the removal of various wastewater contaminants should be investigated.
