Question

3. A FWS constructed wetland is being designed to polish grey water from a school building in Indiana. The grey water characteristics are 80 mg/L BOD, 20 mg/L TSS and 10 mg/L nitrogen (as ammonia nitrogen). They would like their constructed wetland to reduce their BOD to 15 mg/L before the water exits the wetland. No treatment objectives are required for TSS, nitrogen or pathogens in the wetland. Decaying plant matter provides a background BOD concentration (C*) of 7 mg/L. Assume a temperature in the wetland of 12ºC, and a kA,20ºC of 117 m/yr for BOD. The other design parameters are:  Q = 80 m3 /d,  Safety factor multiple = 1.2  Aspect ratio = 8:1  Average water depth (d) = 0.5 m  Bed slope = 1% (0.01 m/m)  Manning’s resistance factor (a) for sparse vegetation of 0.487

Determine the surface area for BOD, nitrogen, and pathogens (the largest area will control the design); increase the area by a safety factor of 20% (multiply by 1.2)

Answer 1

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  G. T Mannis coelhicent (n is a ndton of the den1H ot the etatton ans the OLo Ou tcutor

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  can be ca late4I the en

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  uot land stope ot th