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Catalytic Carbon or Carbon Systems – what they do, how they work, maintenance and benefits
There are 2 main types of carbon systems:
1) Standard Coconut Shell
2) Catalytic Carbon.
City Water – The right system to use depends on the type of sanitization being used by your municipal water supplier. Most water reports will list the type of sanitization used in their water. Both systems will remove odor and a host of other chemicals that may be found in your brew water.
Chloramines: If your city uses chloramines, then you need a catalytic carbon system. Chloramines are a combination of chlorine and ammonia. Standard Coconut shall carbon will remove the chlorine but has a difficult time removing the ammonia. If you go with a standard Coconut Shell carbon system and your city is using chloramines, it could give your beer a slight metal aftertaste. Keep in mind some water companies will use chloramines a couple of months out of the year. A good thing to do is call your water supplier, and ask them if they ever use chloramines.
Carbon systems: If your city only uses chlorine for disinfection, a standard Coconut Shell carbon will do the trick.
Carbon systems – In Depth
Granular activated carbon is commonly used for reducing organics and residual disinfectants from water supplies. This improves taste and protects water treatment components such as reverse osmosis membranes and ion exchange resins from possible damage due to oxidation or organic fouling. Typical surface area for activated carbon is approximately 1,000 square meters per gram (m2/gm). However, different raw materials produce different types of activated carbon varying in hardness, density, pore and particle sizes, surface areas, extractables, ash and pH. These differences in properties make certain carbons preferable over others in different applications. The two principal mechanisms by which activated carbon removes contaminants from water are adsorption and catalytic reduction. Organics are removed by adsorption and residual disinfectants are removed by catalytic reduction. While more expensive, catalytic carbon is far superior for the reduction of chloramines and other contaminants. Catalytic carbon can generally be used in lieu of non catalytic carbon.
Important Carbon System Considerations:
pH: Organics are less soluble and more readily adsorbed at a lower pH. As the pH increases, removal decreases. A rule of thumb is to increase the size of the carbon bed by twenty percent for every pH unit above neutral (7.0).
Particle size: Activated carbon is commonly available in 8 by 30 mesh (largest), 12 by 40 mesh (most common), and 20 by 50 mesh (finest). The finer mesh gives the best contact and better removal, but at the expense of higher pressure drop.
Flow rate: The lower the flow rate, the more time the contaminant will have to diffuse into a pore and be adsorbed. A 20 by 50 mesh carbon can be run at twice the flow rate of a 12 by 40 mesh, and a 12 by 40 mesh can be run at twice the flow rate of an 8 by 30 mesh. When considering higher flow rates with finer mesh carbons, maintain a peak flow of <10 GPM ft2 to mitigate pressure drop issues. Higher water temperatures decrease the solution viscosity and can increase the dye diffusion rate, thereby increasing adsorption. Higher temperatures can also disrupt the adsorptive bond and slightly decrease adsorption. It depends on the organic compound being removed, but generally, lower temperatures seem to favor adsorption.
If you are using carbon replaceable filters, they should be check at least once a month and replaced when needed. When using these types of carbon filters, you need to remember that carbon needs contact time to do it job.
Backwashing carbon or catalytic carbon systems
After a new carbon system is set up you should check your brew water for chlorine on a regular basis. The systems pretty much take care of themselves. When purchasing carbon system sizing is key. There are 2 main factors in sizing the carbon system (1) the flow rate you need (2) your plumbing size. Keep in mind there different grades carbon, cheaper is not better. Always purchase a system with the highest grade carbon and high quality valve. Carbon system should be rebeded every 4 to 5 years.