Activated Charcoal Life

Generally the application is tested under generic conditions....this then gives you the design life of the application you are using....If you can test the water before filter and after for particulate solids, or even more specifically for a particular substance you wish to mitigate, this would answer more specifically then going by the stated design life...

http://en.wikipedia.org/wiki/Activated_carbon

http://extension.uga.edu/publications/detail.cfm?number=B939

http://www.hach.com/

Joe,

I get the sense that you may be a sailor, and have a water purification system on board your boat.

If this is the case, I suggest that you ask your filter supplier this question.

Of course, he wants to sell you filters.

The purity of the water should be monitored, and the filters changed based on their effectiveness.

They work catalytically, so they don't deplete. However, they can degrade over time, depending on the dirt load. Backwashing on the basis of a limiting differential pressure in the forward direction usually works.

Other than that, a planned preventative maintenance regime can be used to determine these things for yourself.

Are you using activated carbon for dechlorination purposes, if that so ...activated carbon (while removing available chlorine) turns to fines. Thus when even when our spargers start passing such fines the product ofcoarse becomes black in colour depicting heavy carbon sludge formation, time to backwash or makeup

If the OP is the least bit pessimistic or at least cautious, install a particulate filter on the down stream side of the activated charcoal filters. AC filters are known to break internally and allow the AC to flow down stream. This results in a genuine MESS within the piping and all the fixtures. This is particularly troublesome if it is on a boat, camper or other vehicle with a limited supply of low pressure water. All fixtures must be flushed if possible, back flushed if not, snaked if flushing is not possible or completely disassembled and washed out. This includes sink faucets, shower valves and heads, tub fixtures, washing machines, dish washers, toilets fill valves, hose bibs, etc. essentially everything including boilers and their input water pressure regulators. The bad part is that there may not be an unclogged outlet to back flush with! Aerators must be taken off and adapters used to back flush, garden hose adapters needed and many other things.

Neighbor has this problem with a big household one. Internal charcoal container mesh broke and spread it all through the piping. Nothing would flow water! We had to run one of my hoses to his house for clean water to flush and back flush. He screwed that up so I had to go and do the job for him. His gratitude was a big basket of "top shelf" booze.

I now always put a particulate filter down stream from an AC filter if it doesn't have an integral interior one. Once is enough for me and it wasn't even mine!

Good Luck, Old Salt

The breaking of mesh sounds rare but anything is possible. Usually, granular activated carbon or GAC is a final process and the pre-treatment is to try to protect the loading on the GAC filter itself. I have seen a large filter in an industrial process installed backwards and something similar happen. The mechanical contractors were embarrassed but did fix the problem. The filter had 100 cubic feet of media. I am sure a downstream particulate filter would have been nice. still the only time I had ever seen a problem in 42 years.

GAC has several problems and backwashing should be kept to a minimum. The biggest reason to backwash is to prevent the filter from stagnating during long periods of non-use. Carbon is an ideal food for many bacteria, molds, yeast, and biological growths. Sometimes these growths are desirable to help remove certain toxins. Like a slow filter, GAC will even form a schmutzdecke that must be backwashed as do biological balls grow within the filter. If they are not stirred up, some breakthrough of the target product removal could bypass or short circuit the GAC media. Injecting H2O2 ahead of the filter could help and actually make the filter work better. In most domestic situations, I have found very few people who understood the GAC process but there are some good people in the business.

Agree. This was the largest residential unit that I had ever seen. The guy always had to have the biggest or finest. With this one the biggest he got was a big mess! Unless a processing system can not accommodate them, I try to put a filter upstream and downstream. Sort of like an insurance policy, if I do it this way I will never need it.

Good Luck, Old Salt

My experience is with air purity where activated charcoal AC is one product useful for the purpose. I have no experience in liquid purification. But AC works on the principle that the pores hold the contaminants being removed. Once full up the AC is no good.

Thus the weight of saturated AC is an indication of how effective it is.

A DIY approach is to take a known volume of fresh AC in a container filled with pure liquid product. Take another container exactly the same size and the same volume of AC that is known to be fully saturated filled with pure liquid. Weigh both accurately. Do the test a dozen times and average the results.

Thereafter weigh only saturated samples from the process and chart the results. Over time a pattern will emerge that could tell you when the AC needs replacing.

The primitive approach is to monitor the process and change the AC when the product fails the quality test.

CAUTION!-- When AC is used in as a vapor filter on the vent of any container, with certain chemicals, there is a risk of FIRE. When the vapor is expelled through the AC some of it can be held on the surface of the AC. When the material is withdrawn from the container atmospheric air, which contains moisture, is sucked back through the AC in order to equalize the container to atmospheric pressure. If the chemical reacts with the water or generates heat with contact with it there is a very strong potential for the AC heating up enough to start a fire with the AC as the fuel.

Depending upon the chemical this can be a potentially dangerous situation. Fires and explosions are not beyond the realm of possibilities. Example is TDI, 2,4-toluene diisocyanate and 2,6-toluene diiso- cyanate.

This happened at a plant I worked at. Unfortunately the engineer who designed this vent system did not know about this. It was up to my my haz-mat responders and myself to put the fire out in the AC container and devise a temporary fix. It got done by a bunch of hands-on people.

Good Luck, Old Salt

Output quality and pressure drop are two indictaions to replace/regenerate the bed.

I only use AC in two places. in the aquarium filter for the goldfish when wintering them over inside the house (not needed this year as the neighborhood cats have apparantly learned how to fish in my outdoor pond) and in the filtered bottle I use when visiting the Scout Camp during the pre-opening work weekend (the water is delivered to the capsites by pipe, it's lean and fresh, but it has a 'rusty' taste to it until the second week of the regular season. the AC filters out the rusty taste). Both filter systems recommend replacing every 30 days, although I believe the bottle filter also recommends replacing after 30 bottle-fulls have passed through the filter. The aquarium I end up replacing every week (those tine goldfish poop like whales, the mechanical filter clogs up before the AC can become 'full' or start releasing the chemicals it's adsorbed(1).) the bottle filter I replace once a year (when I take it out of storage for the camping trip).

Notes:

1) I did not misspell, AC clean the water through ADsorbson, not ABsorbtion. the 'contaminants adhere to the surface of the AC, which is why the carbon is 'activated,' that is, 'made into a honeycomb with a MASSIVE surface area compared to its volume.' From what I know of adsorbsion, the chemicals adsorbed can be released over time, and the fine structure of the AC is fragile and suseptible to breaking down and being carried 'downstream,' along with the chemicals you were trying to filter out, clinging to the AC fragments like castaways hanging on to the sides of a lifeboat.