We have several portable RO's and the carbon tanks in them have a label that says "Activated Carbon". What is activated carbon? How is it different from cocoanut shell carbon or lignite carbon that would be used in other carbon tanks?
Activated carbon is usually made from coal. What they do is crush and heat the raw coal until most of the impurities are burned off, leaving behind pure carbon. Then they "activate" it by heating the carbon again in the presence of steam. The steam burns millions of tiny pores into each piece of carbon, creating channels that increase the surface area tremendously. Think english muffin vs table top. A teaspoon of activated carbon can have a surface area equal to an acre of land. That's 300 ft x 300 ft! Because impurities bond to the surface of the carbon via adsorption, more surface area is better b/c it can do more work. You can make activated carbon out of any living material, but coal has the highest yeild b/c nature has already done most of the work for us by removing most of the other junk that is contained in living cells and leaving behind the carbon.
<growthin act. carbon?>
Posted
So would activated carbon be a better growth medium for bacteria because of all those extra pores and the higher surface area? Could that explain why it is hard to keep portable RO's free from CFU counts above the action level?
<Dr Swiss>
Posted
Good question about growth in activated carbon. Another thing to look at is the water going to the carbon. Is it free of bugs?
How can you disinfect the carbon? Can you run a low pH disinfectant through it? What are the known effects?
On the last two comments. There should be chloramines in the water to keep the bugs down on the city water. That can depend on the water quality where you are at. But as you remove the chloramines in the water say through your first carbon, then there is nothing to keep the bugs down. I have spoke with our vendor's tech support people for our portable ROs, on more than one occasion, that bacteria can be a problem if you are running too much carbon before the RO. Water sits in there and grows stuff. They say that if that becomes the problem you have to use dummy cartridges for the carbon block and completely bypass any external carbon to do an end to end disinfect of the RO. So as far as I know there is no way to clean the carbon. If your bacteria counts are coming back above the action level, you may have a few things going on there. Are they run everyday or do they sit for days at a time? How much carbon do you have before the RO?
