Fundamental Chemistry and Hydraulics - Mathematics and Statistics for the Environment - page 367

■ EXAMPLE 14.24
Problem: At a 12-MGD waterworks, a pump at the rate of 0.20 gpm feeds hydrofluosilicic acid
(H 2 SiF 6 ) as a 23% by weight solution. The specific gravity of the H 2 SiF 6 solution is 1.191. What is
the fluoride (F) dosage?

Solution:

Pump rate = 0.20 gpm × 1440 min/day = 288 gal/day

Fluorideappliedrate = 288 gal/day × 0.23 = 66. 22gal/day

Weight of fluoride = 66.2 gal/day × .34 lb/day 8 × 1.191

6

Weight of water =× /day 12 10 gal × 8.34 lb/gal × 1.

Weight of fluor ide

Weight of water

= ××
××

66 2834 . . 1 191 . 658

10 6

.

Dosage = = = 6.58 mg/L

6

12 10 8 34 × 10 .

■ EXAMPLE 14.25
Problem: 10 mg/L of liquid alum with 60% strength is continuously fed to a raw water flow that
averages 8.6 MGD. How much liquid alum will be used in a month (30 days)?

Solution:

1mg/L1gal/MG =

10
0.60

gal
MG

MG
day

Requiredper day = × = 143 gal/day

14.2 FUNDAMENTAL HYDRAULICS
Water/wastewater operators make pumpage and flow rate calculations during daily operations. In
this section, we describe and perform fundamental pumping and flow rate calculations to review the
foundational principles of advanced hydraulics operations for environmental professionals (intro-
duced later in the text).

14.2.1 p rinCiples oF W ater h ydrauliCs
Hydraulics is defined as the study of fluids at rest and in motion. While basic principles apply to all
fluids, for the moment we consider only those principles that apply to water/wastewater. Although
much of the basic information that follows is concerned with the hydraulics of distribution sys-
tems (e.g., piping), it is important for the operator to understand (and environmental professional to
review) these basics in order to more fully appreciate the function of pumps.

14.2.1.1 Weight of Air
Our study of basic water hydraulics begins with air. A blanket of air, many miles thick, surrounds
the Earth. The weight of this blanket on a given square inch of the Earth's surface will vary accord-
ing to the thickness of the atmospheric blanket above that point. At sea level, the pressure exerted
is 14.7 pounds per square inch (psi). On a mountaintop, air pressure decreases because the blanket
is not as thick.