The Comprehensive Everglades Restoration Plan has identified highly treated wastewater as a possible water source for the restoration of natural water flows and hydroperiods in selected coastal areas, including the Biscayne Bay coastal wetlands. One potential source of reclaimed wastewater for the Biscayne Bay coastal wetlands is the effluent from the South District Wastewater Treatment Plant in southern Miami-Dade County. The U.S. Geological Survey, in cooperation with the Comprehensive Everglades Restoration Plan Wastewater Reuse Technology Pilot Project Delivery Team, initiated a study to assess the presence of emerging contaminants of concern in the South District Wastewater Treatment Plant influent and effluent using current wastewater-treatment methods. As part of the study, 24-hour composite and discrete samples were collected at six locations (influent at plants 1 and 2, effluent pump, reuse train, chlorine dioxide unit, and ultraviolet pilot unit) at the plant during: (1) a dry-season, low-flow event on March 2-3, 2004, with an average inflow rate of 83.7 million gallons per day; (2) a wet-season, average-flow event on July 20-21, 2004, with an average inflow rate of 89.7 million gallons per day; and (3) high-rate disinfection tests on October 5 and 20, 2004, with average flow rates of 84.1 and 119.6 million gallons per day, respectively. During these four sampling events, 26, 27, 29, and 35 constituents were detected, respectively. The following transformations in concentration were determined in the waste stream: -100 to 180 percent at the effluent pump and -100 to 85 percent at the reuse train on March 2-3, 2004, and -100 to 1,609 percent at the effluent pump and -100 to 832 percent at the reuse train on July 20-21, 2004; -100 to -37 percent at the effluent pump, -100 to -62 percent at the reuse train, -100 to -56 percent at the chlorine dioxide unit, and -100 to -40 percent at the ultraviolet pilot unit on October 5, 2004; and -100 to -4 percent at the effluent pump, -100 to 17 percent at the reuse train, -100 to -40 percent at the chlorine dioxide unit, and -100 to -14 percent at the ultraviolet pilot unit on October 20, 2004. Samples were tested for detection of household and industrial (organic) wastewater compounds, pharmaceutical compounds, antibiotic compounds, and hormones in influent. Two 'known' endocrine disrupting compounds?17 beta-estradiol (E2) and diethoxynonylphenol? and four 'suspected' endocrine-disrupting compounds?1,4-dichlorobenzene, benzophenone, tris(2-chloroethyl) phosphate, and tris(dichloroisopropyl) phosphate?were detected during these sampling events. Phenanthrene and indole showed the greatest concentration ranges and highest concentrations for the organic wastewater compounds. Acetaminophen showed the greatest concentration range and highest concentration, and warfarin showed the smallest concentration range for the pharmaceutical compounds. Sulfamethoxazole (a sulfonamide) showed the greatest concentration range and highest concentration, and sulfathiozole (also a sulfonamide) showed the smallest concentration range for the antibiotic compounds. Two hormones, 17 beta-estradiol (E2) and estrone (E1), were detected in influent. Samples were also tested for detection of organic wastewater compounds, pharmaceutical compounds, antibiotic compounds, and hormones in effluent. Indole showed the greatest concentration range and highest concentration, and triphenyl phosphate showed the smallest concentration range for the organic wastewater compounds. Dehydronifedipine showed the greatest concentration range and highest concentration, and warfarin had the smallest concentration range for the pharmaceutical compounds. Anhydro-erythromycin (a macrolide degradation product) showed the greatest concentration range, and sulfadiazine (a sulfonamide) and tetracycline showed the lowest concentration ranges for the antibiotic compounds. One hormone, 17 beta-estradiol (E2), was det