recommendations on the design and
A chemical agent is
added to the water to kill pathogenic
The chemical is usually
chlorine, but iodine may be used.
respect to water supply systems which
The first two parts of a water supply
system are a source and a treatment
The third is a storage
b. Treatment processes. Four steps
The storage requirement is
are generally used in the treatment of
simply one half of the total daily
These are sedimentation,
Both of the last two
steps, filtration and disinfection,
treatment of water.
media, however, will rapidly become
The total daily requirement is divided
by two to reduce the amount of
sedimentation and coagulation, do not
construction effort for the storage
precede filtration. Thus, all four of
facility while still allowing for
these steps are necessary in practice
without continual operation of pumping
and treatment facilities.
however, without the other steps, will
total storage requirement is found,
the water should be stored at two
vulnerability and to allow for repair
and cleaning of the tanks without
is no more than allowing water to
interrupting service. Thus storage is
stand so that particles heavier than
usually best accomplished by using two
the water itself will settle out.
tanks, each of whose capacity is one
takes place when a coagulant (usually
alum) reacts with alkalines in the
10. DISTRIBUTION SYSTEM
water to form a jelly-like mass. This
jelly-like mass, called floc, collects
The last part of a water supply
the smaller, lighter particles and the
system is the distribution system. It
entire mass settles out.
can be classified in two ways by the
is normally considered a separate
type of energy used to distribute the
water, and by the arrangement of the
through sand, diatomaceous earth, or
a. Classification by energy used.
system needs a source above the storage
carbon or charcoal used as a filter
facility so that the water from the
element will remove undesirable tastes
treatment plant may flow by gravity to
and odors from water.
The storage facility must
again be elevated enough above the
This step in
users so that gravity may be used
the treatment process is probably the
again to distribute the water.