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Combined Sewer with a New Reach Learncard 478112176


Question

Description: There are 19,500 inhabitants living in a municipality. The wastewater generated is conveyed through a combined sewer. A reach of this combined sewer located in a short distance upstream of the sewage treatment plant is rehabilitated with following features:


Circular profile: DN 1,000

Length: 800 m

Height difference: 10 m


The screw pump lifting station at the treatment plant has a dry weather inflow of 48 l/s.

How long does it take for the wastewater to flow from the start of the new reach to the screw pump lifting station when the flow velocity during dry weather is 1.7 m/s and during a storm event 3.0 m/s?

Answer

tdw = l/v

tdw = (800 m · s)/1.7 m = 470.58 s → 7.84 min


t
sw = l/v

tsw = (800 m · s)/3.0 m = 266.66 s → 4.44 min



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