The Fate of Wastewater Phosphate in Saline Carbonate Groundwater: Key Colony Beach, FloridaEPA Grant Number: U915145
Title: The Fate of Wastewater Phosphate in Saline Carbonate Groundwater: Key Colony Beach, Florida
Investigators: Elliott, Katherine
Institution: Pennsylvania State University
EPA Project Officer: Hahn, Intaek
Project Period: January 1, 1997 through January 1, 2000
Project Amount: $68,000
RFA: STAR Graduate Fellowships (1997) RFA Text | Recipients Lists
Research Category: Fellowship - Geology , Academic Fellowships , Ecological Indicators/Assessment/Restoration
The objectives of this research project are to: (1) determine whether phosphate derived from injected wastewater is immobilized through interaction with the porous limestone aquifer of the Middle and Upper Florida Keys; and (2) determine the mechanism of uptake if it is observed.
Field and laboratory studies are being conducted to investigate the behavior of wastewater-derived phosphate in the groundwater of the Florida Keys. Laboratory experiments allow for observations of the phosphate-rock interaction under controlled conditions. The experiments test hypotheses used to explain field observations. The field study site is the municipal treatment plant of the city of Key Colony Beach, in the Middle Keys. This facility is one of only two centralized wastewater treatment plants in the Florida Keys. In the plant, treated wastewater is disposed of through a line of six injection wells into the porous limestone aquifer. Seven piezometer nests were installed in the area surrounding these wastewater injection wells. Subsequently, monitoring well samples were analyzed for pH, salinity, nutrients, and oxygen isotopic composition. Results show that both wastewater phosphate and nitrate uptake are occurring in the limestone aquifer underneath the study area; of these, phosphate is the more immobile nutrient. Laboratory experiments are being conducted to understand the mechanism behind the observed phosphate uptake. In these experiments, phosphate-enriched water continuously circulates through a column of Key Largo limestone. Separate experiments are being conducted with phosphate-enriched seawater and phosphate-enriched distilled water. Additionally, one experiment is being conducted using wastewater from Key Colony Beach to investigate the effects of wastewater organic matter.