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Figure 13.Example of a municipal water treatment plant for taste and odor control.

Nonpotable water treatment is also well within the economical applications of liquid phase adsorption systems. There in fact are so many unique examples of process water treatment throughout the chemical industry that we could go on for days discussing speicif systems. One example of process water treatment is shown in Figure 14. This system (designed by CPL Carbon Link, go to www.activated-carbon, com on the Web; a good site with lots of technical information from this supplier!) Shown in Figure 14 shows a process diagram for the removal of creosote and pesticides from the liquid phase in a timber treatment facility. A storage dosing tank is used for smoothing the flow, from where the water is pumped into a chemical dosing system for pH adjustment. Then, ferric sulphate is added to form a precipitate with suspended solids, which is subsequently flocculated by the addition of polyelectolyte.

The water is then pumped through series operated sand filters, which provide the final stage of suspended solids removal and protect the garnualr activated carbon (GAC) filters from particulate contamination. Series operated GAC filters are then used to remove the dissolved creosote and pesticides from the water. To achieve compliance with specifications levels, water should be sampled and analyzed after leaving the first GAC filter. The second GAC filter normally serves as a guard bed.

A final example of application and process layout is shown in Figure 15. In this example the process relies on activated carbon to remove color bodies from a recycled glucose intermediary prior to use in the production of confectionary. The glucose containing the color taint must be mildly heated (to about 70° C), so that the normally solid product becomes less viscous and easier to pump. The syrup is

Figure 15. Example of a decolorization treatment facility.

Filtered syrup is then passed through columns containing GAC using a high residence time (a variation is simply the addition of PAC on an as-needed basis -this obviously has cost advantages for batch operated systems). During these stages the color bodies are physically adsorbed by the activated carbon. When PAC is added to the process, the heated syrup is agitated. Following agitation, the syrup undergoes mechanical filtration to remove entrained PAC prior to the glucose being used to manufacture the confectionary. This is a good example of a pollution prevention technology, because the reprocessing of waste in this manner allows it to be suitable for re-use as a saleable product after further use. This technique is adaptable in diverse applications such as pharmaceutical processes, chemical intermediaries manufacturing and soft drink production.

These examples help to illustrate the versatility of activated carbon in standard water treatment applications. Another application which merits a distinct discussion is groundwater remediation. This is discussed below.

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