AMMONIA REMOVAL PROCESSES FOR URINE IN AN UPFLOW MACROPHYTE SYSTEM

Constructed wetlands represent an alternative technology for the remov al of nitrogen from wastewater, although removal mechanisms are poorly understood. Detailed studies of ammonia removal from diluted urine in a vertical upflow macrophyte system were made in a column fitted with sampling ports, filled with sand, and planted with common reed (Phrag mites australis). Variations in profiles for ammonia, nitrate, and dis solved oxygen were interpreted for a range of initial ammonia concentr ations and loadings. The profiles demonstrate that the previously prop osed mechanism of root oxygenation promoting bacterial nitrification/d enitrification may have been overemphasized. In systems with sufficien t root density and an upflow regime, luxury plant uptake with rhizome storage dominates N removal. Plant uptake of ammonia regulates oxygen demand and provides suitable conditions, both in terms of oxygen and a mmonia concentrations, for additional bacterial nitrification. Consequ ently, higher concentrations and loading rates of ammonia can be treat ed by an upflow macrophyte system as compared to a bacterial system al one.