2018 ASHS Annual Conference

Phosphorous (P) applications in containerized plant nurseries are an essential for the growth of healthy plants. However, due to the low nutrient holding capacity of soilless media, some P not utilized by plants may leach into drainage systems and downstream water bodies where it can contribute to eutrophication and reduce water quality. As environmental regulators establish and enforce nutrient criteria, effective methods are needed to reduce amounts of P in runoff and drainage water. This study investigated the use of a small scale flow-through ferrous iron (Fe(II))-based remediation system to chemically precipitate P. This system was developed as an add-on module to a nitrate-bioremediation system previously characterized (Wilson and Albano, 2013). The add-on duplicate systems were connected to the outflow of the nitrate-removal bioreactors, and consisted of two 242 L tanks containing kaldness media. Water was pumped from a retention pond located within a commercial nursery. Phosphorus was supplied using Peters Professional 20-10-20 fertilizer dissolved in lake water to achieve initial P concentrations of approximately 3-5 mg/L. Tanks were aerated to maintain average redox conditions greater than +50 mV. An Fe(II) solution was injected into the tanks at dosing rates of ~1.3, 2.0, 3.6, and 4.7 mL/min. Multiple samples were collected from inflows, outflows, and within each tank during each treatment evaluation. Filtered samples were analyzed by ion chromatography. Phosphorus removal efficiencies of 66, 78, 95, and 99% were observed for each respective treatment, indicating great potential for this conceptual system at iron dosing rates ≥3.6 mg/min and phosphorus concentrations between 3 and 5 mg/L. This type of system may especially be useful for nurseries with space limitations.