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Mr.Jadi Singh L..i February 11,2003 Page 3 Variables and Assumptions Denitrification is one of many important processes occurring in septic system tanks and leachfields whereby certain bacteria utilize the oxygen in the nitrate(NOO and release nitrogen gas (N2)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 of effluent. Soils with very high sand content and fast percolation rates are estimated to denitrify effluent at a lower rate, about 10 percent to15 percent(Hantzshe and Finnemore, 1991). Due to the presence of highly permeable sandy soils,the denitrification factor is estimated to be 10 percent. An estimate of the quantity and quality of rainfall and effluent is required for the analysis. The C1M1S agricultural information was accessed on the internet for average monthly rainfall and average monthly evapotranspiration (ET) for the Lodi West no. 166 weather station(http//www.cimis.water_ca.gov/). Rainfall average for the Lodi station is given in the San Joaquin County Soil Survey(SCS, 1992). The calculation and assumptions discussed on Plate No. 1, indicate deep percolation of rain in Lodi was estimated to be 7.28 inches. The nitrate concentration of rain fall was estimated to be 1 m /L-N (Hantzshe and Finnnemo,1991). The quantity waste water was estimated to be 3,000 gallons per day(gpd). The average nitrate concentration of a MicroSepTee treatment system averages less than 10 mg/L-N. The United States Environmental Protection Agency (EPA)maximum contaminate level for drinking water is 10 mg/L-N nitrate. Raw septic waste is normally considered to range between 20 to 100 mg/L-N total nitrogen with normal residential use averaging between 35 to 45 mg/L-N total nitrogen. As a result of the analysis, the use of the engineered septic system should not cause a build up of nitrates above the EPA maximum contaminate level for nitrates in drinking water of 10 mg/L-N. The Ne value or average concentration of percolating effluent is 6.9 mg/L-N. Please see Table 2 for a summary of the calculation and Plate No. 2 for the calculation. Table 2. Summary of Nitrate Mass Balance Analysis. Type of facility, *Result: Denitrification Deep Waste Parcel Rain maximum flow Nitrate FactorRain Level to Size Concentrat- Concentration Percol- Septic (ac) ion ation Tank' Gas 6.9 mg/L-N 10% 7.28 10 mg/L- 2.0 1 mg/L-N Station/Convenien inches N cc Store,3,000 gpd• *Note: Maximum contaminate level for Nitrate is 10 mg/L-N(45 mg/L as NO,). �gERso� i P Y W o .