Does anyone have insight as to how to remove bacteria in a system that does not allow the use of biocides? Obviously, water removal is key, but often the bacteria becomes impregnated in the metal and is very difficult to remove. Thoughts?

Greg,

You may want to review the previous article, 15 items below your post, Bacteria in Hydraulic Oil. Posted by Yaron B.

Jim

Thanks for the reply Jim. I read the posting and it had good information, but we are not able to use biocides in this application. I've heard that even after all of the water is removed from the system, bacteria can still remain. Is there any truth to that? If so, how can the pesky little beasts be dealt with?

Out of curiosity, Greg. What kind of system do you have?

Greg.

It is possible to use heat combined with removal by centrifuge/filter. (Purifier)

The following must be noted: (Ref: EC Hill/IMarEST-Microbes in the marine industry: ISBN 1-902536-46-0)

Bellow 70°c there will be little pasteurising effect, but between 70-80°c there can be significant kill; contact time needed at 70°c is 30 sec. or more but only a few seconds are needed at 80°c. There will always be some survivers and these have the potential for furter growth when they return to the main system (reservoir). The purifier should be operated so that the microbes can be killed there at least as fast as they can grow.

Greg,

Apart from Mr Hughes recommendation I would like to add a bit of my experience in managing metal-working oils. If possible (in particular water based fluids) maintain a pH of 8 to 9. At a pH that is Basic, bacteria cannot proliferate. Most lube companies often supply or sell pH boosters along with soluble metal working oils. In most case these are outsourced. "Croton" is a popular brand possibly an ICI product but may not suit your needs as it is classified as a biocide.

Hussam Adeni

Dear Mr. Hughes

Exactly the information that I was looking for. I've ordered the book that you referred to as well.

Much appreciation!

We use centrifuges in conjunction w/ heaters and heat exchangers to effectively pasteurise machining coolants. Same may be applicable.