Virus Occurrence and Transport in a School Septic System and Unconfined Aquifer

Abstract

Federal efforts to establish reliable natural disinfection criteria for ground water supplies require the identification of appropriate indicator viruses to represent pathogenic viruses and an understanding of parameters affecting virus survival and transport in a variety of hydrogeologic settings. A high school septic system and the associated fecal waste‐impacted unconfined sand and gravel aquifer were instrumented to: (1) evaluate if the concentrations of enterovirus and coliphage in this system were sufficient to allow their use as indicator viruses; (2) establish viral transport rates, transport distances, and concentrations in a highly conductive cold water aquifer. Enteroviruses were found in only two of eight assays of the septic tank effluent (0.26 and 4.4 virus/L) and were below detection in eight ground water samples. Male‐specific and somatic coliphage were detectable in both the septic tank effluent (averaging 674,000 and 466,000 coliphage/L, respectively) and in the impacted underlying ground water, decreasing to detection limits beyond 38 m of the drainfield. Virus transport parameters in this aquifer were measured by seeding high numbers of MS2 and ØX174 coliphage into the ground water and documenting their transport over 17.4 m. A portion of the seeded virus traveled at least as fast as the bromide tracer (1 to 2.9 m/d). Proposed natural disinfection criteria would not be met in this aquifer using standard 30.5 m setback distances. In addition, the virus sorption processes and long survival times resulted in presence of viable seed virus for more than nine months.

Domestic wells have high probability of pumping septic tank leachate

“…Violation of these assumptions can lead to increased pollution risk relative to the regulatory assumptions (Yates and Yates, 1989;Postma et al, 1992;DeBorde et al, 1998;Corbett et al, 2002;Lipp et al, 2001). As would be anticipated intuitively, horizontal and vertical set back distances required to meet health standards are most sensitive to horizontal and vertical hydraulic conductivity, and the local hydraulic gradient (Harmsen et al, 1991b,a).…”

“…Water wells in close proximity to septic systems on soils with a very high sand fraction, shallow unconfined aquifers, in karst terrain, or on fractured crystalline rocks are especially vulnerable to contamination by pathogens (Scandura and Sobsey, 1997;DeBorde et al, 1998;Frazier et al, 2002;Miller and Ortiz, 2007;Harden et al, 2008;Humphrey Jr. et al, 2010). Yates et al (1985) and Yates (1991) pointed out that the most common cause of waterborne disease outbreaks in the US is contamination of well water by septic systems.…”

Processes in microbial transport in the natural subsurface

“…Several field investigations of virus transport in groundwater have been conducted at a number of sites (e.g., [6,27,28,109,127] and others previously mentioned), but are not reviewed here. A detailed review of viral transport models, processes, and parameters from field studies is provided by Schijven and Hassanizadeh [110].…”

Review: Microbial biocenoses in pristine aquifers and an assessment of investigative methods

“…bacteriophages to simulate viruses, and microspheres to simulate bacteria and protozoans (e.g. Auckenthaler et al 2002;Craun et al 2002;DeBorde et al 1998;Edberg et al 1997;Flanigan and Rodgers 2003;Flynn 2003;Golas et al 2002;Herwaldt et al 1992;Lillis and Bissonnette 2001;Lisle and Rose 1995;Mahler et al 2000;Nasser et al 1993;Rossi et al 1998;Schaffter and Parriaux 2002;Szewzyk et al 2000).…”