Active carbon sanitization

Sodium Bicarbinate would be the safest method that would not exhaust the carbon bed. You should also look at setting up a backwash schedule for the vessel, start at once a week or when the differential pressure exceeds 10 psi.

The carbon bed currently has a backwash set-up for 75 m3 flow, approximately every 4 days. The carbon bed is used for Chlorine removal before the water going to a RO for purified water generation. Bacteria count is very low before the bed, approx 4 cfu, after the bed it is >200. I have tried a few chemicals but none have managed to kill the bacteria.

Look through this companies site "Avista Technologies". I use several of their products and they have great customer support.

This may not be possible in your design but most large volume bottling plants (such as Sunkist in central California) use UV sterilization as the first stage of bacterial and viral remediation. I Googled UV water sterilization systems and found hundreds of suppliers. Perhaps one of these vendors can supply a system which will help eliminate your bacterial contamination problems. PS these systems are often found in the surplus "food and beverage machinery/equipment" sales areas in eBay and Google.

The carbon bed has a break tank in front of it that is dosed with Sodium Hypochlorite to kill any bugs that come in the supply water. Unfortunately due to a failure in the dosing, some got in and they appear to have colonised the carbon bed. We have a UV down stream of the RO so I know noting is getting out to the storage tank and tests prove this. I just need to kill what is currently in the carbon bed.

Have you tried washing with a hypochlorite solution or some other chlorine-containing solution? Or could you possibly steam-out the bed with high-pressure (and thus high temperature) steam?

The function of this carbon bed is to remove Chlorine. The carbon bed has a break tank in front of it that is dosed with Sodium Hypochlorite to kill any bugs that come in the supply water. Unfortunately due to a failure in the dosing, some got in and they appear to have colonised the carbon bed. As the function of the unit is to remove Chlorine I do not think it possible to use Sodium Hypochlorite to sanitize it. Also as mentioned in the initial post, due to the design of the plant it is not possible to use heat to sanitize this bed.

What about using salt (sodium chloride) solution? It is used to regenerate water softners and also works as a desinfectant.

Slong:

Salt (sodium chloride) as a disinfectant? Where did you learn that?

Has anyone used Oxonia? This is a mixture of Hydrogen peroxide and peracetic acid. It is used as a disinfectant and sanitizer.

It may be time to replace the bed. Depending on operating type (continuous/batch), undesirables content amount (concentration), fluid flow and other factors, the active carbon bed gets saturated. If not the case, backwashing is the normal procedure.

It is known that any halure as salt of its respectively oxacid will kill the bacteria (such chlorine, bromure, etc.), such as NaClO (not NaCl). Only be careful this bactericide will not affect the quality of your fluid downstream.

SaC.