Subsurface flow constructed wetlands generally require less site area for the same flow than do free water surface wetlands. The assumed detention time is 3 days, the water depth is 1 ft (0.3 m), with a media depth of 1.5 ft (0.45 m); the organic loading rate is <72 lb/ac-d (<80 kg/ha-d); and the expected effluent quality is similar to the free water surface wetlands above:
Assf = Site area for subsurface flow constructed wetland (ac; ha). k = Factor (1.73 x 10-5, U.S. units; 1.85 x 10-3, metric). Q = Design flow (gal/d; m3/d).
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