Setting up a TMDL for the Jordan River-The Role of Sediment Oxygen Demand and Nutrient Flux

The Jordan River connects Utah Lake, a fresh water lake, to the Great Salt Lake, and spans almost 57 miles. The river receives runoff from various point and non-point sources and is impaired due to low dissolved oxygen at several locations. The Utah Division of Water Quality is developing a large-scale TMDL for the Jordan River which includes water quality modeling using a QUAL2K model. This software requires input of sediment oxygen demand. The purpose of this study was to evaluate in-situ sediment oxygen demand (SOD) at five sites along the lower tier of the Jordan River. Nutrient fluxes were also estimated from the sediment to the water column during these experiments. An in-situ sediment oxygen demand chamber designed by EPA region IV was employed. Results show that the sediment oxygen demand rate for the various locations along the lower Jordan River was in the range 1.5 to 7.5 g/m2-d. The nutrient flux analysis results gave relatively negligible ammonia concentrations; however, the average nitrite, nitrate and dissolved phosphorus concentrations varied between 0.95 to 1.8 mg/L, 0.75 to 4.8 mg/L and 2.0 to 6.0 mg/L respectively. In addition, sediments collected at a depth of 0 to 4 cm were capable of releasing and taking up phosphorus when exposed to alternate anaerobic and aerobic conditions, indicating the possible presence of Polyphosphate Accumulating Organisms (PAOs) and demonstrating the sediment's ability to release phosphorus to the water column at relatively low DO conditions.