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lr. <br /> March 26,2003 <br /> Job Number:LG02-031 <br /> Page 8 <br /> r <br /> 5.1 Quantity and Quality of Nitrates from Septic System and Rain Fall <br /> •- The average total-nitrate concentration of the typical septic waste is normally considered to be 35 <br /> mg(L-N 8. The average daily flow of influent into the septic systems on the site was determined <br /> by listing the categories of occupancy, duration of occupancy, and estimated domestic waste <br /> water flow associated with each category. The following table lists the assumptions to determine <br /> average daily domestic waste water flow. <br /> Table 4. <br /> Total estimated average daily flow of the septic system. <br /> Category Effluent usage for each category(See Calculation <br /> footnote no. <br /> *- Patients,rehabilitation center. 100 gallons/day/person 50 beds x 100 gpd/bed- <br /> 50 beds,occupancy full time. 5,000 gpd <br /> Employees,Rehabilitation 10 gallons per day(shift)per person 6 people/shift x 3 <br /> 6 people per shift,3 shifts per day,7 shifts/day x 10 gpd/person <br /> days per week. = 180 gpd <br /> Employees,Administration 10 gallons per day(shift)per person (4 people/shift x 1 <br /> 4 people per shift, 1 shift per day,5 shifts/day x 10 gpd/person) <br /> days per week. x 5/7=29 gpd <br /> r Avera a Daily Flow: 5,209 gpd <br /> Note: gpd is gallons per day. The term 5/7 in the calculation column adjusts a 7 day work week to a 5 day work <br /> week. <br /> Denitrification is an important process in septic systems that normally occurs in the leach line <br /> whereby certain bacteria utilize the oxygen in the nitrate(NOO and release nitrogen gas (ND to <br /> the atmosphere. Denitrification is expressed as a percentage, and the normally accepted range is <br /> 10 percent to 35 percent. Soils with higher clay content, moist soil conditions,high pH, and <br /> organic material denitrify about 35 percent and soils with very high sand content and fast <br /> ` s Crites,R.,Tchobanoglous,G., 1998,Small and decentralized wastewater management systems:McGraw- <br /> Hill series in water resources and environmental engineering,McGraw-Hill Boston fust edition,see Table 4-14 page <br /> 181,Typical composition of untreated domestic wastewater. <br /> 9 Crites,R.,Tchobanoglous,G., 1998,Small and decentralized wastewater management systems: <br /> McGraw-Hill series in water resources and environmental engineering,McGraw-Hill Boston first edition,see Table <br /> 4-3 page 172,hospital category for patient and employee. <br /> R� <br /> pFRSQi <br /> A <br /> � Q'R <br /> f• <br />