Environmental Engineering Reference
In-Depth Information
DID YoU KNoW?
Dating back to around 3000 years ago,
qanats
are slightly sloping
tunnels driven into hillsides containing groundwater (e.g., under-
ground aquifers). The qanats rely on gravity to push the water
through open channels to nearby towns or cities.
substantially) use sophisticated control systems to match an unpredictable
demand.
Pumping with storage
is the most common method of distribution
(Mc Ghe e, 1991).
Distribution line Network
Distribution systems may be generally classified as grid systems, branch-
ing systems, a combination of these, or dead-end systems (see
Figure 5.8
).
The branching system shown in
Figure 5.8A
is not the preferred distribution
network, because it does not furnish supply to any point from at least two
directions and because it includes several terminals or dead ends. Normally,
grid systems (see
Figure 5.8B,C
) are the best arrangement for distributing
water. All of the arterials and secondary mains are looped and intercon-
nected, eliminating dead ends and permitting water circulation in such a
way that a heavy discharge from one main allows drawing water from other
pipes. Newly constructed distribution systems avoid the antiquated dead-
end system (see
Figure 5.8D
), and such systems are often retrofitted later by
incorporating proper looping.
Service Connection to Household Tap
A typical service connection consists of a pipe from the distribution system
to a turnoff valve located near the property line (see
Figure 5.9
).
Distribution and Storage
Distribution reservoirs and other storage facilities or vessels are in place to
provide a sufficient amount of water to average or equalize daily demands
on the water supply system (see
Figure 5.10
). Storage also serves to increase
operating convenience, to level out pumping requirements, to decrease
power costs, to provide water during power source or pump failure, to pro-
vide large quantities of water to meet fire demands, to provide surge relief, to
increase detention time, and to blend water sources. Generally, six different
types of storage are employed in storing potable water: clear wells, elevated
tanks, stand pipes, ground-level reservoirs, hydropneumatic or pressure
tanks, and surge tanks.
