Units with a RO/DI system: if for some reason you have to bypass the RO and use only the DI tanks to produce dialysis quality water, do you disinfect the water loop when you bring the RO back on line? Also, if you do disinfect, do you replace the DI tanks after the disinfection? Any comments are appreciated.

It is unclear as to the duration of bypass, if the water (post bypass) has sat stagnant in the RO for any length of time, then it is well worth your while to disinfect. If your DI system is there for emergency back up only, then you will want to put in a new "dry set" for the next emergency. As to your loop, the DI can not give you RO quality water,(microbiologically speaking) as there is no actual barrier to "debug" the water. If the loop has been exposed to microbiological less pure water, it would be well worth your while to perform a disinfection if only to prevent an increased degree of colonization between regular disinfections.

You should have in place, post DI, a UV light unit and at least a 0.2 micron filter. To be on the safe side I would do a disinfection of the loop followed by bacteria sampling at various point of use locations and at the end of the water loop.

Just bringing this topic back up since at one of my units it's currently being discussed. I want to see if theres any new or additional information or opinions on it.

To help clarify the original posting, the water system is composed of a RO followed by DI tanks in a worker/polisher configuration. The DI tanks are always used. If the RO or the water distribution pumps fail, we open and close valves so the chlorine-free water now goes around the RO (bypass) and directly into the worker DI tank. The bypass of the broken component may last anywhere from a few minutes to days depending on how long it takes to rectify the problem.

I can't find any written guidance that addresses this subject so I'm hoping some of the more experienced readers or readers that use the same type of water system can share their knowledge or guidlines. Thanks

We don't have any systems like this but thought I would chime in....

Since you must have UV and submicron filtration anytime DI is used, your product water when your RO is bypassed will be just as bacteria/endotoxin free as if it were online though the filters may become plugged sooner. If the RO repair is pre membranes I wouldn't think it neccessary to disinfect. If the repair is post membrane it MAY actually be required by the guidelines BUT, since you do have the DI's with UV and submicron filters it MAY not be technically required but still prudent.

Chuck

Thanks Chuck.

Actually theres no UV lights post DI, just submicron filters.
Is it stated somewhere that there "must" be UV lights, or, is the UV light requirement a nice to have safety component? This water system is a 501k approved system installed recently.

I was not aware that is a a requirement to have a UV post DI. In what standard is this stated?

DISINFECT any time you change the normal scheme of things.....be safe..

I am certain Florian can update us on the latest AAMI requirements. In the past AAMI has recommended that DI tanks be “followed by an ultrafilter or other bacteria and endotoxin removal device.” A 0.2 micron filter is rated for bacteria removal; it will give very poor endotoxin removal. An ultrafilter rated for endotoxin removal should be used.

UV lights continue to be used in dialysis applications as a relic of past “best” practices when bacteria were considered a threat and biofilm was not appreciated.

The thinking is that if a UV light is used, and kills planktonic bacteria that flow thru it, the remains are pyrogenic and so need an appropriately rated filter should collect this matter.

Keep the ultrafilter and ditch the UV.

A new ultra-filter is now available (.05 micron) that could be placed after the RO/DI and lasts for months (depends on use). For more info, go to http://www.biologicalwaterfilters.com/dialysis-water-filters.php