Objective: To examine how to calculate the relative rates
of blending CAP water with Tucson ground water to yield a
blend with a certain ppm dissolved solids.
Tucson has a blended water program where CAP (Central Arizona
Project) water with a 700 ppm dissolved solids concentration
is mixed with Tucson well water with a 240 ppm average concentration
of dissolved solids. The blend is to have a 400 ppm concentration
of dissolved solids.
One can look at how much CAP water must be mixed with 100
gallons of Tucson well water to get the blended target of
400 ppm. To do this use
Vol. of Chemical in 1 + Vol. of Chemical in
2 = Vol. of Chemical in solution
use Vc = Vw Con to give
We are trying to find how many gallons (X) of CAP water at
700 ppm dissolved solids must be mixed with 100 gallons of
Tucson well water at 240 ppm to yield a blend with 400 ppm
of dissolved solids?
Always keep track of the chemical volumes.
Again clear the 1,000,000 and the gallons from the equations.
This leaves
700X+24,000= (100+ X)400
700X+24,000=40,000+ 400X
Rearrange
300X =16,000
X = 53.3 gallons.
Since Tucson does not mix barrels of water
but rather mixes streams of water, the equations for mixing
streams of CAP and well water are
If the flow rate of Tucson well water is 100
gpm then to find the flow rate of CAP water in gpm we use
Again clear the 1,000,000 and the gpm from the
equations. This leaves
700X+24,000= (100+ X)400
700X+24,000=40,000+ 400X
Rearrange
300X =16,000
X = 53.3 gallons per minute.
Price of Bottled Water
Bottled water is becoming more and more a common place item.
We see many people carrying one in the summer as well as other
times of the year. The cost of a 24 ounce bottle is often
$1. Since there are a little over five of these bottles in
a gallon the price of the bottled water is roughly $5 per
gallon. Some people will drive quite a ways to save 10 cents
a gallon on gasoline, which sells for $1.60 a gallon, but
do not seem to think about what they are paying for water,
three times the cost of gasoline.
The following calculator allows you to estimate the rough
profit in selling bottled water that is obtained out of the
tap in a city. The cost of city water is often in the range
of $2,000 to $6,000 per acre-foot. Remember an acre-foot is
43,560 cubic feet or roughly 326,000 gallons. To run it, first
enter the cost of 1 acre-foot of water, then the cost of 1
plastic bottle. Next, you are asked for the price you will
charge for a 24 ounce bottle of water. The Calculator then
calculates the approximate profit. You can see that this is
very rough as cost for distribution, advertising, labor, facilities,
etc. are not included. Even so, you would have quite a bit
of money to work with if you could sell an acre foot of water
as bottled water.
