Has anybody out there heard of chemicals/molecules that interfere with the colorimeter readings for chlorine/chloramines. I have heard of manganese and another chemical giving "false positives" on these readings. Prinited documentation would be helpful.

I'm not the water expert here but we had a problem with our carbon tanks expiring early (about once a month with backwashable carbon tanks). When we were having the problems some of the people I talked to had me check the following.

Check to see if the municipal water supplier is adding ortho, polyphosphates or oxidized manganese. Also check for tannins and lignins. pH can also be a factor in carbon tanks not performing to expectations. In our area (midwest) we had a problem with our TOC (total organic carbon) being high. Our solution was to install what is known as an organic scavenger. So far to date (it's been about 5 months now) we have had no problems. However, your best bet is to call your municipal water supplier and see if they can help you. If not they can at least get you a list of the chemical contaminants in the water and tell you what they add. With this you can find out more to rectify your problem.

Now on the simpler side... have you verified what you suspect to be false readings with a second meter? Is the reagent expired? Are you using the correct reagent? Correct procedure? I ask about correct procedure because I went to a clinic and found they had been doing it wrong for years because one person did it wrong and showed everyone else how to do it wrong. Nobody ever read the directions. Just throwin out suggestions. Let me know if there's anything else I can do to help. I've been in the carbon tank dilemma before and know it can be a booger. Good luck!!

In several of the facilities that I am associatated with there have been "apparent" low levels of chlorine/chloramine (<0.1ppm)post carbon bank #1 and #2, but essentiallly 0.0ppm post R.O. There have been enough of these incidents to indicate that it is not a testing error or expired reagnets causing the problem. From a surveyor's point of view, if its not true breakthrough, what is it? There should be a test to show that there is an interfering substance involved and that the R.O. is clearing it pre-patient. Whatever it is, manganese or something else, the facility needs to demonstrate that it has things under control or else they may be perceived as operating with exhausted carbon tanks. I plan to contact HACH and LaMotte to see about such tests. Any other suggestions?

Mark,

I'm travleing so I don't have access to my resource material but you can call Hach and request info on DPD interferences. You can also try their website - somehwere along the line I downloaded a paper by Clifford Hach on chlorine testing / DPD methods

Thank you, Dennis. Any thoughts on how to hadle a surveyor when they ask about your "apparent" chlorine breaktrough? I doubt they will be swayed by our charming smiles and good intent!

Mark,

About the surveyor show them your policy on Chlorine Protocol. As long as you are following that you should be fine.

Good luck buddy!