In reference to waterborne diseases, what does
incubation period mean?
What are the two major categories of impurities
Eruptions of the skin and frequent bowel
movements, without fever are symptoms of what
Natural gravity action is the mechanism for what
method of water treatment?
What is the most commonly used disinfectant in
the mechanical diaphragm. The water diaphragm is
always a vacuum type, solution -feed machine and
has the advantages of being friction-free and
punctureproof. The mechanical diaphragm machine
may be either direct- or solution-feed pressure type or
solution-feed vacuum type only.
Direct-feed chlorinators are used chiefly as
emergency equipment and on small installations where
it is not possible to obtain a water supply suitable for
operating a solution-feed machine. They cannot be
used where the pressure of the water being treated is
more than 20 psi and are limited in the types of
semiautomatic and automatic controls that may be
used. Because the chlorine is under pressure as a gas at
all times, direct-feed machines may easily leak gas into
a confined or poorly ventilated space where the
leakage could corrode adjacent equipment and
structures. If you should be called upon to operate a
direct-feed chlorinator, carefully follow the
recommendations and instructions of the equipment
manufacturer. You, as the operator, must be
thoroughly familiar with the equipment to ensure its
proper operation, adjustment, and minor repair.
LEARNING OBJECTIVE: Recognize types,
functions, and safety precautions associated
Chlorination equipment used to feed chlorine gas
or hypochlorite solution may be classified by type,
depending on the methods of control. The three
methods of control are manual, semiautomatic, and
1. The manually controlled type equipment must
be started and stopped manually, and the rate of feed
must be manually adjusted to the rate of water flow.
A solution-feed chlorinator introduces chlorine gas
into the water supply by means of a chlorine solution.
This supply is usually formed by drawing chlorine gas
2. In the semiautomatic type, equipment starts and
stops automatically as water flow starts and stops;
however, it must be manually adjusted to the rate of
water flow. This type is normally used with water
pumped at a fairly uniform rate.
3. In the fully automatic type, the rate of feed is
automatically adjusted to the rate of flow of the water
being treated through pressure of a metering device.
In a!! three types, the ratio of feed to water treated,
or dosage, is set by manual adjustment.
into a jet stream of water at the low-pres
injector mechanism of the chlorinator.
sure point of the
The chlorinator (figs. 7-5 and 7-6) controls and
indicates the rate of flow of chlorine; provides a simple
means of manually setting the feed rate; mixes chlorine
gas and water; and delivers the solution to the point of
application. Figures 7-7 and 7-8 show a typical
cylinder connection and scales.
The chlorinator operates under a vacuum,
produced by a flow of water through the injector. The
installation must allow a 5-inch vacuum.
Chlorinators may also be classified generally by
type of feed. Here you have two types of machines
DIRECT-FEED and SOLUTION-FEED. Direct-feed
machines are designed to operate without a pressure
water supply, feeding the chlorine gas directly into the
flow to be treated. Solution-feed machines dissolve the
gas in a minor flow of water and inject the resultant
solution into the flow to be treated and require a
pressure water supply for operation.
Chlorine gas under pressure enters the chlorinator
at the chlorine inlet connection where it is electrically
heated to reduce the deposit of impurities and to
prevent reliquefaction of the gas when the chlorinator
is shut down with the supply turned on. Chlorine
expands into a gas at a ratio of 1:460; that is, 1 cubic
inch of chlorine expands into 460 cubic inches of gas.
This volummetric expansion can rupture lines. For the
same reason, there should be no dips or traps in any
Another method of classifying chlorinators is by
the type of diaphragm used in controlling the chlorine
feed. There are two types-the water diaphragm and