Drip Dispersal Wastewater Systems in Tennessee 

Many rural wastewater treatment systems are failing, according to state report 

Report on the Performance of Wastewater Systems Utilizing Drip Dispersal in Tennessee

June 7, 2024

Land Based Systems Unit, Division of Water Resources Tennessee Department of Environment and Conservation

Executive Summary

Beginning in the mid-1990s and continuing to present the State of Tennessee has been issuing permits for systems relying on drip dispersal technology to transmit wastewater to the soil environment in a manner that does not constitute direct discharge to surface water or groundwater. The soil environment provides treatment of the wastewater and facilitates its return to the environment. For most of these systems, drip dispersal is the sole means by which wastewater is managed. These systems have been largely used in support of residential subdivisions with other rural establishments such as churches, schools, and businesses also relying on this technology. Performance of these systems, relative to their permit conditions, has been and continues to be highly variable.

One of the most challenging aspects of operating these systems within permit conditions involves the ability of the soil to receive and transmit the applied wastewater away from the point of application without resulting in prolonged soil profile saturation or ponding of wastewater on the surface of the ground. In many cases these ponded conditions result in overland flow of wastewater away from the identified land application area. Noncompliance of this type is particularly critical as in many cases the wastewater flows onto adjacent properties, residential yards, or drainageways and surface waters, but is not treated to levels or sampled at frequencies that are required for discharging systems.

The Tennessee Department of Environment and Conservation’s Division of Water Resources conducted a survey of 420 land application areas supporting 374 land application systems in the state in January and February of 2024. The purpose of this statewide survey was to observe the hydraulic performance of the soil profile component of these systems and report the results in a manner that may inform design engineers, operating entities, local governing bodies, and future standard development.

Fourteen of the 374 permitted land application systems were either not in use or had not been constructed. Site observations at the remaining 360 land applications systems indicate approximately one-fourth of the systems exhibited notable performance issues, including wastewater not being appropriately controlled and, in many cases, leaving the land application area and entering adjacent properties and/or drainageways or surface waters; approximately one-fourth of the systems exhibited less severe, but nonetheless noncompliant issues such as localized saturation and ponding or areas that were overgrown preventing evaluation; and approximately one-half of the active systems did not exhibit any indication of noncompliance.

Full Report

Report on the Performance of Wastewater Systems Utilizing Drip Dispersal in Tennessee (tn.gov)