Environmental Engineering Reference
In-Depth Information
Note:
The weight of a gallon of the process chemical is usually printed on the
container label or the material safety data sheet (MSDS), or weight per gallon can
be determined if the specific gravity of the chemical is supplied.
Requiredamount (lb/day)
Wei
Feed rate (gpd)
=
(2.15)
ght (lb/gal)
Requiredamount (lb/day)
Wei
Feed rate (gpm)
=
(2.16)
ght (lb/gal)
×
1440 min/day
Requiredamount (lb/day)
×
3785 mL/gal
Feed rate (mL/min)
=
(2.17)
Weight (lb/gal)
×
1440 min/day
■
Example 2.102
Problem
: To achieve phosphorus removal, the plant must add 812 lb of ferric chlo-
ride feed solution each day. The ferric chloride solution weighs 11.1 lb/gal. What is
the required feed rate in gallons per day? In gallons per minute? In milliliters per
m inute?
Solution
:
812 lb/day
11.1 lb/gal
Feed rate (gpd)
=
= 73
gp
d
812 lb/day
11.1 lb/gal
Feed rate (gpm)
=
=
005
.
gpm
×
144
0 min/day
812 l
b/day
×
×
3785 mL/gal
Feed rate (mL/min)
=
= 192 mL/min
11.1 lb/gal
1440 min/day
WIRE-TO-WATER CALCULATIONS
In the past, wire-to-water calculations for pumping systems were seldom considered
except for very large pumps where the wire-to-water efficiency of the pump-motor
combination was of significant importance. The emergence of the variable speed
drive, digital electronics, and higher electrical costs has made wire-to-water effi-
ciency invaluable for smaller pumping systems. Thus, wire-to-water calculations are
important in water/wastewater operations where large and small pumps are used for
numerous applications (Rishel, 2001). The term “wire-to-water” refers to the conver-
sion of electrical horsepower to water horsepower. The motor takes electrical energy
and converts it into mechanical energy. The pump turns mechanical energy into
hydraulic energy. The electrical energy is measured as motor horsepower (mhp). The
mechanical energy is measured as brake horsepower (bhp), and the hydraulic energy
is measured as water horsepower (whp).
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