SU0002196 SSNL - Laserfiche WebLink

Home Browse Search

�. June 21,2000 Job Number. L000-173 Page 12 In a septic system's leach line trench, denitrification is the favorable biological process in which certain bacteria utilize the oxygen in the nitrate(NO,) and release nitrogen gas(N2)to the atmosphere. Denitrification is expressed as a percentage and the normally accepted range is 10% to 25%. In other words, about l0a/o to 25% of nitrates in the effluent are converted to gas due to the biological activity. Soils with higher clay content, moist soil conditions, and organic material denitrify 25% or more and soils with higher sand content and fast peculation rates are less favorable and are estimated to denitrify about 10%or less. Due to the presence of silty soils and the percolation rate observed,the denitrification factor is estimated to be about 20 %. To determine the concentration of septic effluent for the project, the standard concentration of 45 mg/L-N for septic influent will be added to the ground water background level of 0.047mg/L-N then multiplied by a factor 0.8 reflecting the 20% denitrification reduction. The concentration of the septic system percolate is estimated to 36.0 mg/L-N after denitrification. Table 6. Mass Balance Calculation Nitrate Source Rate Nitrate-N Concentration For Analysis Standard Units (Metric) Agriculture NA NA NA NA Winery wash Conservativel 9.9 mg/L-N 137 gals/day @ 9.9 519 L/day @ 9.9 water y Assume mg/L-N mg/L-N, 50,000 gallons 5,138 mg-N/day per year or 137 gals/day _ Septic System 26,280 gal/yr Average septic influent 72 gallons/day 273 IJday @ 36,0 or 72 gals/day nitrate level+ground water @36.0 mg/L-N mg/L-N (denitrification nitrate level=total septic (after denitrification factor of 20%) level. 45mg(L-N+0.047 200%reduction) 9,828 mg-N/day mg/L,-N* (1-0.20)=36.0 mg/L-N Deep 7.86 in/yr on 0.17 mg/L-N 44.275 cf rain/day 1,253,871 L/dav percolation of 20 acres. @ 0.17 mg/L-N rain 570,636 cf/year 213,158 mg-N/day (Total weight mg-N/Total volume water L=Average Concentration mg/L-N) 0.18 mg/L-N 228,124 m -N/ 1,254,663 L= 1 11 NoteThe agricultural system existing on the site is considered in balance and does not leach nitrogen. ?�E FJO i E ,SSOL