Reference no: EM13305550

A family of six in a five bedroom house would like to treat their wastewater in an onsite septic system, constructed wetland, and tile drainage (leach field) system. They will be generating a maximum of 1.2 m3/d of septic tank effluent. The septic tank effluent characteristics are 140 mg/L BOD, 50 mg/L TSS and 40 mg/L nitrogen (as ammonia nitrogen). They would like their constructed wetland to reduce their BOD to 15 mg/L and their nitrogen to 10 mg/L before the water enters the tile drain/leach field. No treatment objectives are required for TSS or pathogens in the wetland. The available gravel medium has a K of 9,144 m/d, with a porosity of 0.42. Decaying plant matter provides a background BOD concentration (C*) of 7 mg/L. Assume a wastewater temperature in the wetland of 12ºC, a kA,20ºC of 117 m/yr for BOD, and a kA,20ºC of 10 m/yr for nitrogen. Assume an AR of 0.5:1, a bed slope of 0.5% (0.005 m/m), and a freeboard of 0.2 m. The depth to groundwater is 4 m, and a soil percolation test in the area that they would like to place the leach field reveals a percolation rate of 4.9 min/cm. Design a SSF constructed wetland and a tile drain /leach field system for this house.