a sewer line has a flow rate of 1.25 MGD (million gallons per day). Convert this to cfs(cubic feet per second)

Question

i cant seem to figure out how to get the answer. i feel like ive gotten about half of it but after that i seem to be at a loss. if i could be shown the process of this i would really like to know how to solve it

Answer 1

Conversions of rate work kind of like fractions.

miles/gallon * gallons / minute gives you the new unit of miles/minute....as if the denominator of the first fraction cancels out with the numerator of the second fraction.

 

The other trick is that sometimes you need to divide the fractions since dividing by a fraction is the same as multiplying by the reciprocal. For example.

26 miles/gallon divided by 4 quarts / gallon = 26miles/gal * .25gal/quart = 6.5 miles/qt.

 

So for your problem, we need the conversions 7.480519456gal/cu. ft. or the reciprocal, 1 cu ft/7.480519456gal.

 

1,250,000 gal/day * 1/7.480519456 cu ft/gal = 167100.695 cu ft/day. Now convert days into seconds.

How many seconds in a day? 24hour/day * 60 min/hour*60 sec/min = 86400 sec/day.

 

Notice these numbers need to be divided. cu.ft/day divided by sec/day = cu ft/day * day/sec = cu ft/sec

SO.......167100.695 divided by 86400 =1.934035822 cu ft/sec.

 

Hope this helped

 

Answer 2

The thing to do here is keep the units straight first

 

so you need to go from millions of gallons per day - to cubic feet per second

 

Lets start with days - -> seconds

 

1 day *  (24 hours/ 1day) * (60 min /1 hour ) * (60 sec/ 1 min) 

 

you can mulitply everything through and see that the units all cancel and you are left with seconds.

 

Then you need to convert  gallons to cubic feet - look that up to be  7.48 gallons in cubic foot

 

1.25 million gallons * ( 1 cuft / 7.48 gallons) 

 

This will give you the number of cubic feet

 

divide the cubic feet by the seconds and you get    ## cuft/sec

 

If you still have ? post what you have so far and we'll go through it in more detail.

 

HTH

 

DonnaNJ