State Water Resources Research Institute Program

Project ID: 2008TN52B
Title: Effect of Wastewater Strength on Soil Physical Properties when using Subsurface Drip Irrigation
Project Type: Research
Start Date: 3/01/2008
End Date: 8/31/2009
Congressional District: TN Second
Focus Categories: Wastewater, Non Point Pollution, Water Quality
Keywords: Drip Dispersal, Domestic Wastewater, Decentralized Wastewater Management
Principal Investigator: Buchanan, John R.
Federal Funds: $ 25,000
Non-Federal Matching Funds: $ 62,338
Abstract: The focus of this project is the use of drip irrigation technologies for the dispersal of domestic wastewater to the subsurface soil. Applying domestic wastewater to the subsurface soil has three basic goals: (1) the soil is a highly-reactive media that provides final treatment of wastewater, (2) the soil minimizes human contact with the potential pathogens in wastewater, and (3) the soil disperses renovated water back into the hydrologic cycle. Drip irrigation is known to provide a uniform water application at a rate that minimizes both temporal and spatial saturated soil conditions.

Two subsurface wastewater drip dispersal research sites have been established and have been receiving wastewater for approximately three years. The first site is in Rutherford County, Tennessee and represents a heavy textured, poorly structured clay soil. The second site is in Blount County, Tennessee, and it is located on a silt loam soil with moderate structure. At each site, two sub-systems have been installed such that half of the site receives septic tank effluent and the other half receives secondary-quality effluent. The primary question to be answered by this project is whether secondary treatment is needed before subsurface drip irrigation. Can the advantages of subsurface drip overcome the soil's limitation to provide renovation before the water reaches a limiting boundary (a restrictive layer)? Further, will the physical tubing serve as a limitation - will higher strength wastewater cause failure within the tubing and/or emitters? This project will attempt to address these questions by conducting extensive soil sampling within each of application fields, and by disinterring the sections of drip tubing. Soil sampling will be three-dimensional, sample locations will be chosen with respect to the horizontal and vertical distance from point-source emitters. These samples will be analyzed to determine any differences in hydraulic, organic, nutrient, and biological differences.

Progress/Completion Report, 2008, PDF
Progress/Completion Report, 2009, PDF

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