Leaching of Contaminants in a Soil Amended with Tomato Packinghouse Wastewater.

Florida produces about 635 million kg of fresh tomatoes (34% of US total) each year for domestic supply, with a total value of $464 million. About 70 tomato packinghouses in Florida use 36,340 to 68,137 liters of freshwater per day to clean the field grown tomatoes before packing, which, in turn, generates about 151 million liters of wastewater each year. Approximately 54% of this wastewater is sprayed onto the tomato fields and 31% is discharged into sewers. Due to the sandy nature of Florida soils, there are concerns that land application of wastewater may result in leaching of wastewater applied nutrients and metals and contaminate ground water supplies. Our objectives in this study were to 1) determine the nutrients and trace metals leaching in a sandy soil irrigated with tomato packinghouse wastewater and 2) investigate the distribution of nutrients and metals in different soil horizons. We packed 12 PVC soil columns (30 cm diameter and 50 cm long) in two soil horizon increments (Ap and E) of a Zolfo fine sand (sand: 92–93%, silt: 0.2–0.4%, and clay: 6–8%). Soil was air-dried and mixed before packing in the soil columns to achieve the field bulk densities of 1.77 g/cm³ for Ap horizon and 1.87 g/cm³ for E horizon. This resulted in similar porosity (0.31 for Ap; 0.29 for E horizons) and particle density (2.60 g/cm³ for both horizons) in the packed soil columns as field conditions. Soil columns were irrigated for 35 days in four treatments that included a control (de-ionized water) and three application rates of wastewater at 0.84 cm per day (below state recommended level), 1.68 cm per day (at state recommended level), and 2.52 cm per day (above state recommended level) in triplicate. Leachate was collected every day following irrigation for 35 days and analyzed for pH, EC, nitrogen, phosphorus, copper, zinc, nickel, iron, calcium, magnesium, potassium and chromium. This presentation will discuss the concentrations and loads of nutrients and metals in the leachate and the potential of ground water contamination from wastewater application. Results will provide information to tomato industry and state regulators about the leaching potential in wastewater applied fields and will aid in development of best management practices to reduce leaching losses of nutrients and metals, prevent ground water contamination, and protect Florida’s water resources.