This research attempts to garner a better understanding of the nature and dynamics of the microbial habitats effecting nitrification and denitrification within an artificial wetland treating domestic sewage. The wetland studied is a top loading vertical flow submerged bed system located in Highland, NY, USA. Redox potentials are measured with platinum tipped probes installed at 15, 30, and either 45 or 60-cm-depth within each bed. Temperature, pH, dissolved oxygen and precipitation data are measured on site. System influent and effluent samples from each of the four treatment units are collected weekly. Sand samples are collected at five locations within each treatment unit, for microbial measurements, which include denitrifier enzyme activity (acetylene blockage), nitrification potential (chlorate blockage), and microbial biomass (simultaneous chloroform exposure and extraction). Mean influent wastewater values over a 2-year period have been 293.7 mg L-1, 72.1 mg L-1, 116.2 mg L-1 and 16.5 mg L-1 for BOD5, TSS, NH4+ and PO43-, respectively. Mean effluent values for BOD5 and TSS have been <4 mg L-1 and <1 mg L-1, respectively. Eh values at the 45-cm-depth are lower in the fourth bed (second Phragmites bed) than in the second bed (second Phalaris bed), with mean Eh values of 65.8 ±58.4 mV and 295.1 ± 67.4 mV, respectively.