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18 Januar 2021 AdvancedGeo <br /> January An Employer-Owned Company <br /> Project No. 05-1278 <br /> Page 2 of 3 <br /> DENITRIFICATIONS CAUSED BY SOILS <br /> The process of denitrification is important when utilizing subsurface septic lines and <br /> regularly occurs in the soil within the leach fields where bacteria utilize oxygen in the <br /> nitrate to release nitrogen gas out to the atmosphere. The denitrification process is <br /> controlled by waste concentrations, soil type, annual rainfall, pH of the soils, total organic <br /> concentration of the soil (TOC) and exposure time to nitrogen. The soils with a high or <br /> moderate clay content, higher organic content, high pH, and adequate soil moisture <br /> denitrify the concentrations by approximately 20 to 30 percent and less desirable soils <br /> with more sands and faster percolation rates (less moisture and clay content) denitrify <br /> only about 10 percent. A denitrification factor of 25 percent was selected for the <br /> calculation based on the sandy loam soil existing at the site. <br /> MASS BALANCE OF NITROGEN LOADING <br /> The EHD requires the user to consider all potential sources identified for wastewater <br /> generation. Further, the EHD supports the use of Hantzsche/Finnemore, or other <br /> appropriate formula/model to calculate a mass of nitrogen loading. <br /> RESIDENTIAL: <br /> The Hantzsche / Finnemore (Nr) equation for residential home application: <br /> Nr = IxNw (1-d) + RxNb = (I+R) <br /> Definitions: <br /> Nr = The average concentration of nitrate-nitrogen in the recharged wastewater parts per <br /> million of nitrate-nitrogen. <br /> I = Volume rate of wastewater entering the soil averaged over the gross developed area <br /> (acres) in inches per year. The total wastewater volume for proposed project will be <br /> 1,350 gpd + 600 gpd x 365 days of proposed operation = 1,950 x 365 days - 7.48 gallons <br /> per cubic foot = 95,154 cubic feet of wastewater. Does not account for evapotranspiration <br /> likely to occur. <br /> NW = Total nitrogen concentration of wastewater at 85 mg/L-N based on the average <br /> discharge. <br /> d = Fraction of nitrogen concentration removed from the wastewater due to denitrification <br /> within the soil (25 percent for loamy soils). <br /> R = Estimated Deep percolation / average rainfall recharge rate per year: 11 .78 inches. <br />