Viral tracer studies indicate contamination of marine waters by sewage disposal practices in key largo, Florida

Abstract

Domestic wastewater disposal practices in the Florida Keys are primarily limited to on-site disposal systems such as septic tanks, injection wells, and illegal cesspits. Poorly treated sewage is thus released into the highly porous subsurface Key Largo limestone matrix. To investigate the fate and transport of sewage in the subsurface environment and the potential for contamination of marine surface waters, we employed bacteriophages as tracers in a domestic septic system and a simulated injection well in Key Largo, Florida. Transport of bacteriophage ⌽HSIC-1 from the septic tank to adjacent surface canal waters and outstanding marine waters occurred in as little as 11 and 23 h, respectively. Transport of the Salmonella phage PRD1 from the simulated injection well to a canal adjacent to the injection site occurred in 11.2 h. Estimated rates of migration of viral tracers ranged from 0.57 to 24.2 m/h, over 500-fold greater than flow rates measured previously by subsurface flow meters in similar environments. These results suggest that current on-site disposal practices can lead to contamination of the subsurface and surface marine waters in the Keys.

Human enteric viruses in groundwater indicate offshore transport of human sewage to coral reefs of the Upper Florida Keys

“…Contamination of offshore marine waters may be due to a variety of sources including ocean outfalls, run-off, illegal dumping from marine vessels or contaminated groundwater discharge. Given that there are no outfalls and little land surface to promote extensive run-off in the Upper Florida Keys, the most likely sources of faecal pollution are boats and contaminated groundwater, associated with septic systems and injection wells (Lapointe et al, 1990;Paul et al, 1995b;1997;. In 2002, the Florida Keys National Marine Sanctuary was designated a No Discharge Zone for sewage from all marine vessels under the Clean Water Act (USEPA, 2002).…”

“…Therefore, while recreational boaters could contribute to some of the observed contamination it is unlikely that this would account for the frequent observation of human enteric viruses in groundwater wells. Alternatively, several tracer studies have revealed that viruses in septic tanks and injection wells in the Florida Keys can reach distances up to and exceeding 3922 m within 27 h (Paul et al, 1995b;1997;, which suggests that wastewa- . Each bar is subdivided to represent the relative contribution of positives from coral surface mucopolysaccharide layers (SML) (n = 5), surface water (n = 5) and groundwater (n = 5) to this total.…”

“…Lapointe et al, 1990;Griffin et al, 1999;Jiang et al, 2001;Lipp et al, 2001), little is known about the migration and impact of this sewage to offshore reef environments. Several researchers have shown that nutrients (especially nitrogen) and microbial indicators of faecal pollution migrate from septic tanks into the groundwater and nearshore surface waters of the Keys (Lapointe et al, 1990;Paul et al, 1995b;1997;. In a series of seeded tracer studies, migration of dyes and bacteriophage consistently showed reef-ward transport through the subsurface (Paul et al, 1995b;1997;Dillon et al, 1999).…”

“…Several researchers have shown that nutrients (especially nitrogen) and microbial indicators of faecal pollution migrate from septic tanks into the groundwater and nearshore surface waters of the Keys (Lapointe et al, 1990;Paul et al, 1995b;1997;. In a series of seeded tracer studies, migration of dyes and bacteriophage consistently showed reef-ward transport through the subsurface (Paul et al, 1995b;1997;Dillon et al, 1999). Viral tracers travelled at rates ranging from 35 m h -1 in Key Largo to 141 m h -1 in the lower Keys, and migrated at least 2500 m (Paul et al, 1997;Paul et al, 2000).…”

Development of a genetically modified bacteriophage for use in tracing sources of pollution

“…lithium salts) or radioisotopes. There are numerous examples of the successful use of the technique (Skilton and Wheeler 1988;Ijzerman et al 1993;McKay et al 1993;Paul et al 1995;Harvey 1997).…”