Laserfiche WebLink
Where: <br />Nr = Resultant average concentration of nitrate -nitrogen in recharge water - (ppm NO3-N) <br />I = Volume rate of wastewater entering the soil averaged over the gross developed area in in/yr <br />Nw = Total nitrogen concentration of wastewater in mg N/L <br />d = Fraction (%) of nitrate -nitrogen combined loss in the soil due to denitrification. <br />R = Estimated Annual Rainfall Recharge. <br />Nb = Background nitrate -nitrogen concentration of rainfall recharge, exclusive of wastewater influences <br />(ppm NO3-N). <br />Values and Assumptions: <br />I = 420 gpd x 365 d/yr = 153,300 gals/yr = total WW/yr = 20,495 cu ft = 1.29 in/yr <br />4.38 Ac x 43,560 sq ft/Ac x (1 ft/12 in) <br />Nw = 62 mg N/L <br />d = The soil test results indicate a 96% decrease in soil nitrogen concentrations between the 3 ft and 23 <br />ft depths (44 ppm to 2 ppm), attributable to denitrification and used in the Nr equation below. <br />R = 8.82 in/yr. <br />Nb = Assumed to be 0.1 ppm NO3-N <br />1.29 in/yr (62 mg N/L) 0 - 0.96) + (8.82 in/yr x 0.1 mg1L) <br />Nr = (1.29 in/yr + 8.82 in/yr) <br />Nr = 0.4 ppm as nitrate -nitrogen (NO3-N) or 1.8 ppm as nitrate (NO3) <br />It is to be noted that even if a generally accepted denitrification value of 30% was used in the equation <br />above (30% is typically used when soil chemistry data was not conducted), the average concentration of <br />nitrate -nitrogen in the effluent recharge water (Nr) would amount to 5.6 ppm NO3-N, or approximately <br />one-half of the Maximum Contaminant Level (MCL). <br />IV. O.W.T.S. OPERATIONAL PARAMETERS AND. COMPONENTS <br />A. PROPOSED ONSITE WASTEWATER TREATMENT SYSTEM OPERATION <br />SSS§ 3.7. All influent originating from each source (toilets, basins/sinks, showers, laundry, etc.) <br />should discharge into a 2,000 gallon, two compartment septic tank. Effluent from this tank gravity <br />flows into a 1,200 gallon, two compartment septic tank before final discharge to the soil occurs. <br />A Polylok® PL -122 effluent filter shall be placed on the 1,200 gallon tank outlet. The filter should <br />be cleaned when the septic tank is pumped, and possibly sooner. <br />Page -6- <br />Chesney Consulting <br />