Many streams in the low deserts of Arizona are dominated by municipal sewage effluent. Constructed wetlands can provide lower nutrient and contaminant levels to meet wildlife habitat uses. A 1.2 ha pilot and demonstration wetland was constructed to test the feasibility, and develop operating parameters for a full scale wetland to treat sewage effluent. The objective of this study was to determine the effects of pH and redox on sustainability of vegetation. The wetland was replanted in July of 2003 with four species of bulrush (Schoenplectus spp.). Combination ORP-pH sensors and thermocouples were installed in the sediment at eight locations and three depths (0, 75 and 150 mm below the sediment surface) in December 2003. Sensor readings were logged every 30 min. Seasonal and diurnal patterns were evident in both pH and ORP values. The diurnal patterns observed in pH were predominantly in the sediment surface and to a lesser extent at 75 mm below the sediment surface. The pH 150 mm below the sediment surface varied between 6.6 and 7.0, while the pH of the sediment surface and 75 mm below the surface varied between 6.2 and 7.0. The lowest pH values were observed in the summer. Diurnal patterns were present in the ORP readings only in the spring. Unlike pH, diurnal variations occurred 150 mm below the sediment surface and to a lesser extent at the 75 mm depth. The ORP readings were highest in spring and lowest during summer. The seasonal patterns of both pH and ORP appear to be driven more by floating vegetation and bottom growing algae than by the emergent vegetation.