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USE OF SEPTIC SYSTEMS IN SANDY SOILS WITH A SHALLOW WATER TABLE

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Paper number  701P0104,  . (doi: 10.13031/2013.15801)
Authors:   A. E. Morey, A. Amoozegar
Keywords:   Septic System, Mound System, Shallow Water Table, Wastewater Disposal

Many sandy soils in the eastern United States are characterized by a seasonally high water table. The goal of this study was to assess the fate of selected wastewater constituents under a septic system in a sandy soil with a shallow water table. A septic system consisting of a sand filter and a mound installed near the shoreline of a major river, in the Lower Coastal Plain region of North Carolina, was evaluated. The soil at the study site was characterized and observation/sampling wells were installed at different depth intervals below the water table. The site was visited biweekly for 15 months. During each visit, soil water content in the upper 60 cm of the soil was determined by time domain reflectometry (TDR) technique, and the water level in each of the observation/sampling wells was measured before purging the well. Then, temperature, dissolved oxygen (DO), and electrical conductivity (EC) of the water in each well were measured before collecting a sample for laboratory analysis. The ground water samples were analyzed for nitrate, ammonium, and chloride. Overall, the total hydraulic head at the center of the mound was higher than the two sides indicating the formation of a ground water mound under the drainfield area. Immediately below the water table, nitrogen was mostly in the form of nitrate, but at deeper depths the ammonium form was dominant. The soil at the site showed little attenuation for chemical constituents of wastewater. The results for total dissolved solutes and individual ions indicate that dilution rather than soil attenuation is likely the main mechanism in maintaining a relatively low concentration of various inorganic chemicals that enter ground water as a result of the application of wastewater.

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