The need for continuous and dependable disinfection has been
stressed. The chlorination system can fail for a number of
reason, and, therefore, the design of the system must include
the necessary provisions to either prevent failures or allow
immediate corrective action to be taken. Although assured
reliability is essential, design provisions for the this are
often slighted.
1) Chlorine Supply
As a chemical feed process, one
of the most frequent interruption is treatment is caused by
the exhaustion of the chlorine supply. Five features are essential
to maintain continuous chlorine feed: (1) an adequate reserve
supply of chlorine sufficient to meet normal needs and bridge
delivery delays and other possible contingencies; (2) chlorine
container scales; (3) a manifold chlorine header system; (4)
an automatic device for switching to a full chlorine container
when the one in use becomes empty; and (5) an alarm system
to alert operating personnel of imminent loss of chlorine
supply. Without them it is not possible to assure uninterrupted
chlorine feed even with full time operator attendance and
no equipment breakdowns.
The chlorine header system is needed
both to provide a connected on-line chlorine supply which
is adequate to assure uninterrupted flow of chlorine for whatever
period that the system may be unattended and to allow switchover
to a full cylinder without interruption of chlorine.
2) Power Supply
Power outage usually results in
water supply failure which in turn automatically shuts down
the chlorination system. A range of special provisions can
be employed to assure reliability of power and water supply
depending upon the particular situation. These may be in the
form of standby power source and pumps.
3) Standby Equipment
The design of the chlorine feed
system should provide for continued operation in cases of
equipment failure. Where both pre-and post chlorination are
to be practiced, separate chlorination systems should be provided
for each plus a standby system. If pre chlorination is not
to be continuously used, it may be possible to use this system
as the standby system for disinfection. The units, piping,
and accessories should be designed with this application in
mind. If pre chlorination must be carried out continuously
or if no pre chlorination is to be done, a standby system,
capable of replacing the post chlorination system during repairs,
maintenance, or emergencies should be provided. Standby equipment
of sufficient capacity should be available to replace the
largest unit during shutdowns. This includes standby pumps
for the ejector water supply. In addition to standby equipment,
the equipment manufacturer should be consulted regarding vulnerable
components. These components should be a part of the plant's
inventory of spare parts.
4) Water Supply
As mentioned above, during a power
failure the ejector water system will be shut down unless
there is an alternative supply that does not require power,
such as an elevated tank. Standby equipment to provide ejector
water in the event of a power failure would consist of an
engine-driven ejector supply pump. Every ejector water supply
system should have such a standby pumping unit. There is no
way to operate the chlorination system without an adequate
water supply.
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