Page 203 - Facility Piping Systems Handbook for Industrial, Commercial, and Healthcare Facilities

WATER TREATMENT AND PURIFICATION

WATER TREATMENT AND PURIFICATION 4.39

1. Physical. Physical characteristics related to the appearance of the water include color,
turbidity, taste, and odor. Physical quality is corrected mostly through the use of various
types of filters.
2. Chemical. The chemical characteristics of water are related to dissolved minerals
(mostly hardness), gases, and organics. The chemical quality of water is adjusted by the
use of water softeners, ion exchange, RO units, and activated charcoal units to remove
organic impurities.
3. Biological. This characteristic is concerned with microorganisms that will affect the
health of the consumer. Biological treatment requires the use of biocides and biostats
to eliminate and reduce the number of microbes present in the water and to create a
residual amount of the chemical to maintain the required level of action required by
code.
4. Radiological. This is concerned primarily with radon in areas where the water may
have come in contact with radioactive substances. Retention and aeration will lower the
radon count to acceptable limits in approximately 8 h.
A synopsis of general treatment methods for small potable water systems that shows
general advantages and disadvantages is given in Table 4.9.

DOMESTIC WATER TREATMENT FOR SMALL,
PRIVATE RESIDENCES

1. Water with less than 1.0 grains per gallon (gpg) is considered soft.
2. Water containing 1.0 to 3.4 (gpg) is considered slightly hard.
3. Water containing 3.5 to 6.9 gpg is considered moderately hard.
4. Water containing 7.0 to 10.5 gpg is considered hard.
5. Water containing more than 10.6 gpg is considered very hard water.

Domestic water is treated with home water softeners. This generally involves the use
of an ion exchange water softener, called a cation exchange unit. After a period of use, the
softener must be regenerated. This is done by reversing the flow of water through the unit,
called backwashing with a brine solution.

WATER PURIFICATION

This section will discuss pure water used for laboratory and pharmaceutical purposes. The
various systems will be broadly defined and general guidelines for their production, stor-
age, and distribution will be provided.
Ultrapure water used in production of food products and electronics industries is outside
the scope of this handbook. For information on guidelines for water purity in the electronics
industry, refer to the Semiconductor Equipment Manufacturers Institute, Mountain View,
California.
The total water treatment system consists of three interrelated phases: pretreatment,
purification, and distribution (including posttreatment). Purification methods include distil-
lation, ionization, membrane filtration, and other approved processes. WFI water can only
be produced by distillation or membrane filtration. Processes needing ultrapure water used

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