The Survival of Enteric Viruses in Septic Tanks and Septic Tank Drain Fields

The persistence of enteric viruses in a functioning septic tank system was followed using poliovirus type 1 as a model. Poliovirus was incubated in dialysis membrane chambers suspended both in the chambers of a septic tank and in groundwater observation wells strategically placed in the adjacent drainfield. Poliovirus was also incubated, in situ, in the sandy loam drainfield soils to monitor virus movement and inactivation. Attempts were made to isolate indigenous enteric viruses from the septic tank and drainfield groundwater.

Indigenous enteric viruses were regularly recovered from the septic tank. Seeded poliovirus type 1 survived in the septic tank environment long enough to enter the drainfield. Viruses introduced into the drainfield remained infective for extended periods and moved with groundwater flows. Poliovirus incubated in shallow groundwater was rapidly inactivated, but contact with soil seemed to have a protective effect. A consistent disagreement between the results from laboratory experiments and field studies was noted.

The septic tank system used lay in the flood plain of the Rio Grande, within the Elephant Butte Irrigation District. Movement of indigenous enteric viruses through drainfield soils and into shallow groundwater during the initiation of irrigation-season river flows was reported.

Project No. A-052-NMEX