A settling tank has an influent rate of 0.6 mgd. It is 12 ft deep and has a surface area of 8000 ft². What is the hydraulic retention time?

hydraulic retention time,τ=28.67 hours

Explanation:

The hydraulic retention time  τ (tau),  is given as  The volume of the settling tank(V) divided by the influent flowrate(Q)

τ =V/Q

But Volume is not known  and is given as

Volume =  surface area  x depth of the tank

= 8000 ft² X 12 ft

= 96,000 ft³

Also, the influent flow rate is in mgd ( million gallons per day), we change  it to  ft³/sec so as to be in same unit with the volume in ft³

1 million gallons/day = 1.5472286365101 cubic feet/second

0.6mgd =  1.5472286365101 cubic feet/second  x 0.6

=0.93cubic feet/second

τ =V/Q

96,000 ft³/0.93 ft³/sec

τ=103,225.8 secs

changing to hours

103,225.8 /3600 =28.67 hours

The hydraulic retention time =28.67 hours

answer:

try looking it up that is always

explanation: