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May 25,2001 Job Number:LGOl-115 Page 10 analysis are shown on Plates 17 and 18. The units of nitrate used in the mass balance equation are nitrate-N whose maximum drinking water contaminate level is 10 mg/l. Denitrification is an important process in septic systems that normally occurs in the leach line whereby certain bacteria utilize the oxygen in the nitrate(NO3) and release nitrogen gas (NZ) to the atmosphere. Denitrification is expressed as a percentage, and the normally accepted range is 10 percent to 35 percent. Soils with higher clay content, moist soil conditions,high pH, and organic material denitrify about 35 percent and soils with very high sand content and fast percolation rates are estimated to denitrify at a lower rate, about 10 percent to 15 percent. Due to the common occurrence of clayey surface soils,the denitrification factor is estimated to be about 25 percent. An estimate of the quantity and quality of effluent is required for the analysis therefore the following information was used in the calculation. The deep percolation of rain was estimated to be 5.65 inches and the calculation is shown on Plates 14 through 16. The nitrate concentration of rain fall was estimated to be 0.17 mg/L-N.' ,. Nitrates from Septic System The quantity of effluent waste water was estimated to be 50 gallons per person per day. A home was estimated to include as many as 5 persons so the daily total is about 250 gallons(See Table 5). The average nitrate concentration of the typical residential septic waste is normally considered to be 45 mg/L-N.',s Table 5. Total Estimated Effluent. (see worksheets in Appendix for calculations) Category Quantity People Daily effluent quantity for each analysis Residence 50 gallons/day/person 5 50 gallons/day/person x 5 people=250 gallons/day s Otis,R.J.,Boyle,W.C., 1980,Design manual,onsite wastewater treatment and disposal systems:U.S. Environmental Protection Agency,EPA 625/1-80-012. (See page 100,table 6-1). r z e