Abstract
Tomato packers often struggle to find ways to reuse the large volumes of wastewater generated during the tomato cleaning and sanitizing processes due to high transportation costs for off-site disposal and strict surface water discharge regulations in Florida. Information about the composition of tomato packinghouse wastewater and the likely sources of major wastewater constituents might provide insights to develop environmentally sustainable practices for wastewater reuse. The objective of this study was to characterize the chemical composition of wastewater generated in tomato packinghouses. The wastewater samples were collected for 6 to 8 hours from dump tanks of two representative packinghouses at 30 minute intervals after start-up of packing operations during May-June 2009. Results showed that wastewater had high electrical conductivity (1.3 - 2.8 dS·m–1) and chloride (255 - 1125 mg·L–1) due to the use of chlorine as a sanitizer in the packinghouses. Concentrations of total phosphorus (P, 2.8 - 5.7 mg·L–1) and copper (Cu, 1.9 - 2.2 mg·L–1) in wastewater were elevated due to tomato cleaning and sanitizing. To reduce P and Cu concentrations, treatment or blending of wastewater may be needed before discharging wastewater to surface waters. Concentrations of P, potassium, calcium, magnesium, zinc, iron, and manganese were much higher in packinghouse 1 as compared to packinghouse 2 wastewater, probably due to the greater contact time of tomatoes with the dump tank water. Whereas concentrations of Cu were similar in both packinghouses wastewater. Greater concentrations of chemical constituents in the wastewater suggest that residues of pesticides, insecticides, and/or foliar-applied micronutrients on tomatoes may be the likely external sources of most constituents (especially P, Cu, and Zn) in wastewater.
Highlights
Population growth and limited water resources have led to the practice of reusing domestic wastewater to meet irrigation needs of urban, agricultural, and industrial sectors in many US states, especially in Florida, California, Texas, and Arizona
Results suggest that electrical conductivity (EC) and Cl were elevated in the wastewater because of the use of chlorine sanitizers in the dump tanks
The concentrations of wastewater constituents were relatively higher in PKG 1 than PKG 2, which were mainly due to greater contact time of small-sized tomatoes with dump tank water in PKG 1
Summary
Population growth and limited water resources have led to the practice of reusing domestic wastewater to meet irrigation needs of urban, agricultural, and industrial sectors in many US states, especially in Florida, California, Texas, and Arizona. Florida is recognized as a national leader in domestic wastewater reuse, boasting more than 3400 Florida Department of Environmental Protection (FDEP) permitted wastewater facilities (61% domestic, 39% industrial). These facilities reclaim wastewater for a wide range of beneficial purposes such as landscape and agricultural irrigation, groundwater recharge, and industrial uses [1]. High biological oxygen demand, high total soluble solids, and toxic chemical residues present in industrial wastewater require specialized treatments [2]. Wastewater from swine lagoon facilities has high levels of nutrients, N (472 mg·L–1) and P (61 mg·L–1), which require biological and chemical treatments [4]
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