BOD REMOVAL IN FLOATING AQUATIC MACROPHYTE-BASED WASTE-WATER TREATMENT SYSTEMS

Floating macrophytes cultured in ponds used for secondary wastewater treatment (BOD//5 removal) apparently serve two functions: they provide a substrate for bacterial attachment, and their vascular lacunae act as a conduit for the transport of O//2 from the atmosphere to the wastewater. In the present study, floating macrophyte systems containing pennywort (Hydrocotyle umbellata) were found to be 10% more effective (on an annual average) at removing wastewater carbon (BOD//5) than those containing the more productive water hyacinth (Eichhornia crassipes). This enhancement in BOD//5 removal is thought to be due to pennywort's superior O//2 transport capability. In a separate six-month long study, plant harvesting was found to have no effect on BOD//5 removal in a water hyacinth-based treatment system. These data demonstrate that operational strategies used in floating macrophyte-based nutrient removal systems (i. e. , frequent harvest of highly productive plants) are inappropriate for those systems utilized for carbon removal.