Rapid movement of wastewater from on-site disposal systems into surface waters in the Lower Florida Keys

Viral tracer studies have been used previously to study the potential for w astewater contamination of surface marine waters in the Upper and Middle Fl orida Keys. Two bacteriophages, the marine bacteriophage phi HSIC and the S almonella phage PRD1, were used as tracers in injection well and septic tan k studies in Saddlebunch Keys of the Lower Florida Keys and in septic tank studies in Boot Key Harbor, Marathon, of the Middle Keys. In Boot Key Harbo r, both phages were detected in a canal adjacent to the seeded septic tank within 3 h 15 min of the end of the seed period The tracer was then detecte d at all sampling sites in Boot Key Harbor, including one on the opposite s ide of U.S. Highway 1 in Florida Bay, and at an Atlantic Ocean beach outsid e Boot Key Harbor. Rates of migration based on first appearance of the phag e ranged from 1.7 to 57.5 m h(-1). In Saddlebunch Keys, phi HSIC and PRD1 w ere used to seed a residential septic tank and a commercial injection well. The septic tank tracer was not found in any surface water samples. The inj ection well tracer was first detected at a site most distant from the seed site, a channel that connected Sugarloaf Sound with the Atlantic Ocean. The rate of tracer migration from the injection well to this channel ranged fr om 66.8 to 141 m h(-1). Both tracer studies showed a rapid movement of wast ewater from onsite sewage treatment and disposal systems in a southeasterly direction toward the reef tract and Atlantic Ocean, with preferential move ment through tidal channels. These studies indicate that wastewater disposa l systems currently in widespread use in the Florida Keys on rapidly contam inate the marine environment.