Applications

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.

Industry

Description

Use

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

Brewing

Potable water treatment

Removal of trihalomethanes (THM) and phenolics

Industry

Description

Use

Semi-conductors

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

Petrochemical

Recycling of steam condensate for boiler feed water

Removal of oil and hydrocarbon contamination

Groundwater

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.

Oisinjevfen cwlMtor_Dis'iiiju'ion p'.THU

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

Oisinjevfen cwlMtor_Dis'iiiju'ion p'.THU

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.

SLnph;*e CArtXfl

ifitc^dt Charrfcw ^.v Water with Replaceable Turnci

OUtet ':> ifert. Visit! Datritsui&n Pipi-i

Waste Management And Control

Waste Management And Control

Get All The Support And Guidance You Need To Be A Success At Understanding Waste Management. This Book Is One Of The Most Valuable Resources In The World When It Comes To The Truth about Environment, Waste and Landfills.

Get My Free Ebook


Post a comment