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March 6,2001 <br /> Job Number: L.G00-426 ' <br /> Page 9. <br /> r' 3 , <br /> The Hantzsche and Fennemore 6.equation takes into account development area, soil <br /> denitrification factor,rainfall volume, rainfall nitrate concentration, the waste effluent quantity; <br /> and waste effluent nitrate concentration. The formula, assumptions and calculations used for the <br /> analysis are shown on-Plates 8 through 13. The units of nitrate used in the mass balance equation <br /> are nitrate-N whose maximum drinking water contaminate Ievel is 10 mg/l. <br /> Denitrification'is an important process in septic systems that mostly occurs in the leach <br /> line whereby,certain bacteria utilize the oxygen in the nitrate (NO3) and release nitrogen gas (Nz) <br /> to the atmosphere. Denitrification is expressed as a percentage, and the normally accepted range <br /> is 10 percent to 35 percent. Soils with higher clay content,moist.soil conditions, p <br /> high H, and <br /> g <br /> organic material denitrify about 35 percent and soils with very high sand content and fast <br />'t percolation rates are estimated to denitrify at a lower rate, about 10 percent to 15 percent. Due to <br /> the common occurrence'of dark colored(organic layer) clayey surface soils, the denitrification <br /> factor is estimated to be about 25 percent. <br /> An estimate of the quantity and quality of effluent is required for the analysis therefore , <br /> we used the following information for our calculation. The deep-percolation of rain was <br /> estimated'to,be 7.86-inches and the calculation is shown ori Plate 8. The nitrate concentration of <br /> rain fall was estimated to be 0.17mg/L-N.6 ,The average residence.size wasassumed to be a four <br /> (4)bedroom home with a maximum occupancy of 5,people. A typical.quantity of 50-gallons/day <br /> per person was assumed for sewage inflow to the septic system. The average nitrate <br /> concentration of the typical septic waste is normally considered to be 45 mg/L-N.' <br /> F <br /> - d <br /> U.S. Environmental Protection Agency(EPA). 1980. Design Manual:On-Site Wastewater Treatment <br /> and Disposal Systems.Report No.EPA-625/ 1-80-012. 390 pp. <br /> ji <br /> � r <br /> O � <br /> " .iE <br />