Tomato Packinghouse Wastewater: Characterization and Contaminant Leaching Studies.

Land application of wastewater is a beneficial practice to recycle wastewater.  In Florida tomato packinghouses, approximately 230 million liters of wastewater is generated each year during cleaning and packing of tomatoes.  High transportation costs for off-site disposal of wastewater and strict surface water discharge regulations are critical issues associated with the management of packinghouse wastewater in Florida.  Information about the composition of packinghouse wastewater, likely sources of major wastewater constituents, and the effects of land application of wastewater on water quality might provide insights to develop environmentally sustainable practices for reusing wastewater. Our objectives were to (1) characterize wastewater generated in tomato packinghouses and (2) evaluate the leaching potential of wastewater P and trace metals in a sandy soil. Wastewater had high EC (1.3–2.8 dS m^-1) and chloride (255–1125 mg L^-1) due to the use of chlorine gas as a sanitizer in the packinghouses. Concentrations of P (2.8–5.7 mg L^-1) and Cu (1.9–2.2 mg L^-1) in wastewater increased as more tomatoes were washed. Analysis of leachate collected from packed soil columns (50 cm long x 30 cm diameter) irrigated for 30 consecutive days with wastewater at three different application rates (low: 0.84, medium: 1.67, high: 2.51 cm day^-1) showed that soil acted as a sink of wastewater applied P, Cu, Mn, and K, whereas Ca, Mg, Fe, and Zn were not retained in soil and vertically transported in columns.  Application of wastewater at low and medium rates (i.e., up to 1.67 cm day^-1) did not affect leaching behavior of P, Cu, and Fe, whereas Ca, Mg, K, Mn, and Zn losses increased by 2–7 times. Application of wastewater at higher application rate (2.51 cm day^-1) increased leaching losses of all metals (P, Cu, Ca, Mg, K, Na, and Zn) by 1.3–3 times.  This suggests that long-term application of wastewater at the higher application rate will increase leaching of P, Cu, and Zn and could potentially cause groundwater contamination. However, packinghouse wastewater can be safely applied to sandy soils at 1.67 cm day^-1 without significant concerns of increased P and Cu leaching.