Sustainable Phosphorus Management in Land Applied Reclaimed Water Scenarios

Abstract:

Florida leads the nation in wastewater effluent/reclaimed water use, at over 700 million gallons per day, of which 75% is land applied. While these effluent waters are treated to reduce pathogen loads, phosphorus (P) concentrations can still be substantial in long term application scenarios. Currently an estimated 1.5 million kg of P are reintroduced to the landscape yearly (at effluent = 2 mg P/L), compared to only 23,000 kg that would be applied if landscapes were irrigated with ground water (at ground water = 0.03 mg P/L). Research suggests that under long term applications of P systems can reach a state at which they are no longer able to assimilate further loading, potentially resulting in landscapes that are actively leaching and eroding P rich particulate matter to receiving hydrologic systems. This can be especially relevant in Florida given the large proportion of sandy soils that contain, relatively, low physical and chemical ion exchange capacity and high hydraulic conductivity, thus increasing the potential for water quality impairment. Due to increasingly stringent surface water P concentrations allowances, and the many uncertainties regarding the long term fate and transport of P, this research seeks to determine how different soil conditions and reclaimed water loading amounts can alter P leaching profiles in Florida. Field sampling at reclaimed water sprayfield sites are used to determine the relative change in P sequestration potential using soil-phosphorus saturation capacity (SPSC) analyses and potential leaching risk is determined by soil core experimentation. The resulting information improves fundamental understanding of soil-phosphorus transport dynamics and provides insights into alternative techniques for long term environmental sustainability of reclaimed wastewater usage.