The City recently changed water treatment methods and is putting out water testing at 9.0 - 9.3 pH !! They are also treating the water with chloramines instead of chlorine. Our facility buys City water and softens it before piping it up to my dialysis RO system.

Feed water pH has risen in the last several weeks from 7.0 to 7.5. Hardness of treated water remains at 0mg/L and both Tot Chl & Free Chl are still 0.

Will the pH continue to rise and, if so, what should I be concerned about? Thanks!

First, you must determine that your carbons have the proper EBCT to remove the chloramines. Also, keep in mind that the adsorbtion capabilities of the carbon will decrease w/ an increase of the PH.
As for the PH issue, a PH value approaching around 8.5 can result in the production of hydroxide alkalinity. This is not a salt and will pass through the RO membranes resulting in a high product conductivity. One way to determine if this is happening is to compare the feed PH to the product PH, a higher product PH will occur w/ the production of hydroxide alkalinity. If this becomes a problem consult your water treatment vendor about buffering the feed water.

EBCT is appropriate and verified with our vendor, USFilter. To date, pH has still not risen past 7.6 and remains at 7.2 on average. I've not checked product pH and agree that would a good indicator of a change that should be investigated.

Although not yet a problem, my concern is that pH may eventually rise to levels that require an immeadiate remedy. I want to be prepared with a solution.

Our vendor has stated that they do not recommend acid drip systems and that they believe there to be only two solutions. More carbon ( a lot more!) or switching to anthracite carbon (VERY expensive!).

Not many responses on this thread! Must not be anyone else out there that is encountering this problem.

VaTech,

I don't have any personal experience with acid feed systems though I do know of 4 facilities that have them and have no problems at all. I would suggest giving Don Bechtel @ Marcor a call 1-800-752-1402.

Chuck

I used to work for a facility in Texas where the incoming city water pH routinely ran at about 8.0-9.0 and sometimes higher (10 being the highest I'd seen). The incoming total chlorine level was approximately 3-5 ppm (yes that's three to five parts per million, lol). Even with chlorine levels and pH that high we never had a problem. Feed TDS to the RO was usually about 300-350 ppm. Permeate TDS never got above 4 ppm and all AAMI water analysis came back great. Permeate pH was always optimal. Never had any problems. Carbon tanks were set up for rebed every 3 years or sooner if needed but never did we need it sooner. Call it crazy but it didn't give us any problems. Carbon tanks were no larger than what you would normally need for that particular water system. The system had the correct EBCT and everything. Knowing that, the advice I leave to you is just get some carbon just in case and wait it out and see what happens. I know carbon isn't cheap by any means but it's better to have it if you do need it. And besides, it'll get used eventually. Hope that helps and good luck.