Applications of carbon adsorption go far beyond conventional water treatment applications which we will discuss in a general sense shortly. Table 8 provides a summary of the key applications of carbon adsorption systems for liquid phase applications.

Table 8. Liquid Phase Applications of Carbon Adsorption.




Potable water treatment

Granular activated carbons (GAC) installed in rapid gravity filters

Removal of dissolved organic contaminants, control of taste and odor problems

Soft drinks

Potable water treatment, sterilization with chlorine

Chlorine removal and adsorption of dissolved organic materials


Potable water treatment

Removal of trihalomethanes (THM) and phenolics





Ultra-high purity water

Total organic carbon (TOC) reduction

Gold recovery

Operation of carbon in leach, carbon in pulp, and heap leach circuits

Recovery of gold from tailings dissolved in sodium cyanide


Recycling of steam condensate for boiler feed water

Removal of oil and hydrocarbon contamination


Industrial contamination of ground water reserves

Reduction of total organic halogens (TOX) and adsorbable organic halogens (AOX) including chloroform, tetrachloroethylene, and trichloroethylene

Industrial wastewater

Process effluent treatment to meet environmental discharge standards

Reduction of total organic halogens (TOX), biological oxygen demand (BOD), and chemical oxygen demand (COD)

Swimming pools

Ozone injection for removal of organic contaminants

Removal of residual ozone and control of chloramine levels

The most common application of carbon adsorption in municipal water treatment is in the removal of taste and odor compounds. Figure 12 provides an example of a process flow diagram for a municipal water treatment plant. In this example water is pumped from the river into a flotation unit, which is used for the removal of suspended solids such as algae and particulate matter. Dissolved air is the injected under pressure into the basin. This action creates microbubbles which become attached to the suspended solids, causing them to float. This results in a layer of suspended solids on the surface of the water, which is removed using a mechanical skimming technique. Go back to Chapter 8 if you need to refresh your memory on air flotation systems.

Air Floatation And Precipitation

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Figure 12. Process flow sheet for municipal water plant in Europe.

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Figure 12. Process flow sheet for municipal water plant in Europe.

The next step in the process involves the production of ozone bypassing high tension, high frequency electrical discharges through air in specially designed units. Ozone is injected into the water to provide bactericidal action and to break down the natural humic compounds that are the cause of taste and odor problems. The water then passes through a rapid gravity filtration system filled with activated carbon (GAC), which adsorbs the compounds resulting from the ozone treatment. Following adsorption, the water is disinfected for supply to the distribution network. Understand that treatment plants are unique, in many ways like oil refineries - i.e., design basis can be substantially different depending on the nature of the water being treated. Figure 13 provides another example of a municipal water treatment facility using PAC. Again the plant is used for the removal of taste and odor compounds.

There are regions where the treatment of water is intended for potable purposes is not necessary at all times during the year. The presense of taste, odor and naturally occurring toxins largely depends on the biological action in areas where lake or reservoir water supply is common. In these situations it is more cost effective to use intermittent dosing of activated carbon into the water during those times of the year where it is needed. The use of PAC is preferred in these case, mainly because no costly fixed bed filtration equipment is required. The PAC can be dosed directly to existing flocculant tanks at a prescribed rate to achieve the level of pollutant removal required.. Shown in Figure 13, following the dosing of PAC the activated carbon is removed as part of the flocculation process, or it can be filtered out by mechanical means. The final stage of water treatment is disinfection, whereupon the water is pumped to the distribution network.

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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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