2nd UF Water Institute Symposium Abstract

Submitter's Name Sherry Brandt-Williams
Session Name Poster Session: Optimal Use of Integrated Water Supplies 1
Category Optimal use of integrated water supplies
Poster Number 405
Author(s) Sherry Brandt-Williams,  SJRWMD
  Robert Godfrey,  Idea Integration
  Erich Marzolf, SJRWMD
  Reuse Water in the Middle St. Johns River Basin Watershed
  Redirecting wastewater treatment plant effluent from direct discharge into rivers and lakes to reuse systems is a valuable practice in this era of water supply concern. It reduces stress on aquifers and reduces nutrient loads to increasingly impaired water bodies. However, reclaimed water can have extremely high phosphorus concentrations. Nitrates and TN are also higher than most rivers, lakes and estuaries can assimilate. Combined with high irrigation rates, reuse can generate substantial nutrient loads to waterbodies. Nutrient impairment harms both natural ecosystems and human uses of these systems. One example of the magnitude of phosphorus loading to the state‚Äôs waters is found in the Lake Jesup watershed, a large, nutrient-impaired water body along the St. Johns River. A reclaimed water irrigation rate of one inch twice per week has an estimated annual runoff of five metric tons of phosphorus into the lake. This load is equivalent to ~60% of the reduction required under the current TMDL for Lake Jesup. In this poster, quantitative GIS and reclaimed water flows and concentrations are used to estimate nutrient loads and runoff for the entire nutrient-impaired Middle St. Johns River basin. In the current climate of concern about water supply, the use of reclaimed water for irrigation is an important means to reduce potable water demand. However, because of the potential for excessive nutrient runoff due to over fertilization (resulting from the combination of reclaimed water and regular lawn fertilization), recommended fertilizer applications should be reevaluated and consumers educated how they can save money by using less fertilizer. Further, wastewater utilities should be encouraged to improve treatment efficiency so that excessive nutrient loads distributed via reuse within watersheds and springsheds are reduced. Estimated loads presented will be beneficial in prioritizing this initiative.