Page 187 - Facility Piping Systems Handbook for Industrial, Commercial, and Healthcare Facilities

WATER TREATMENT AND PURIFICATION

WATER TREATMENT AND PURIFICATION 4.23

Activated Carbon Filtration
Activated carbon is used to remove dissolved, nonionic organics such as residual chlorine
disinfectants, trihalomethanes, and chlorimines, as well as a major portion of naturally
occurring dissolved organic material, from municipal water supplies. The nonionic organ-
ics tend to coat ion-exchange resins and all types of membranes. For additional discussion,
refer to Activated Carbon Filters in Chap. 3.
System designers are reluctant to use the activated carbon filter in the generation of
PW because of the development of significant levels of bacteria in the unit itself. This can
be controlled by periodically sanitizing with pure steam or hot water with a temperature
greater than 80°C. The need for sanitizing can be determined only by testing the water.
Because of this sanitizing, the interior of the filter housing should be lined or coated. When
using potable water as feedwater, stainless steel housings should be avoided because of the
possible chloride stress corrosion and chloride pitting resulting from the chlorine in the
feedwater. A typical detail of a packed bed activated carbon unit is illustrated in Fig. 4.5.

ION EXCHANGE AND REMOVAL

Ion exchange is the basic process where specific ions in a feedwater stream are transferred
onto an exchange medium called resin, and exchanged for different ions of equal charge.
When the ion exchange process is used to treat water only for removal of hardness, it is
generally known as water softening. When the ion exchange process is used to treat water

FIGURE 4.5 Schematic detail of large-scale granular activated carbon filter.

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