A question of pH

Question: I have a question about treatment devices for high pH levels, but I would like to know who to direct any specific questions to?

Michelle Moyer
Norristown, Pa.

Answer: There are any number of sources I could send you to as your question, while it may not seem so, is very broad. For instance, I might want to know what type of application the treatment might involve, i.e., residential, municipal, commercial, industrial. Is there a specific use for the water? And do you know what’s causing the high pH? A growing number of companies post technical articles and literature on their websites that may prove invaluable to you such as Osmonics, ResinTech, Morton Salt, Calgon Carbon, Atlantic Ultraviolet (which requires free registration), Hach/GLI—to name only a few. GLI International, for instance, contributed one from its online “library” to our magazine that we ran in our October 2002 issue (see “pH Control Systems: Six Options for Small Operators,” Joe Novak, p. 66).

EXTRA: Thanks for your quick response. I work for the water quality division of a county health department enforcing our well regulations and I have a residential customer who has an elevated pH of 9.4. This is unusual for her location because usually we see low pH. We did discuss the possibility of the well driller getting grout into the well, which could contribute to the elevated levels so we are looking into that avenue. But if that is not it and they need to permanently treat for this, we are unclear as to what type of treatment devices are available to treat alkaline water. Let me know if you need any additional info and I will also look into some of the companies that you mentioned. I have already put in a request to get a copy of the article you brought up.
—Michelle Moyer

The Editors: One member of WC&P’s Technical Review Committee suggests that a pH of 9.4 in the feed water would certainly mean that some hydroxyl alkalinity has crept into the system. A highly alkaline grout or cement might be the cause and it may only be temporary. A strong base anion exchanger operating in the chloride (salt) form would convert alkaline anions to chlorides, effectively reducing the pH to neutral or slightly acidic.

Another member suggests that the pH problem should be addressed by making water measurements. Many problems in water and air need to be addressed by making laboratory measurements. Ideally, this water has been analyzed previously to obtain baseline information about the chemistries in the water. Unfortunately, there is a lack of measurements being made and results in a “blame game” of assigning the problem instead of having analytical data to make decisions. In conclusion, we need to be better at providing on-site and laboratory-based testing services to assign the water problem and the most cost-effective solution to the problem.

Lastly, a third member suggests prior to any treatment recommendation he would want to establish why the pH was as high as it is. There are a number of reasons why it could be—such as a temporary well intrusion, or that the well had been worked on and sanitized recently, or simply that the pH reading was in error. A few ground rules: 1) pH must be conducted on-site, at the well on freshly drawn water and with a pH meter that is calibrated. 2) If the well has been worked on (or is new), any chlorine disinfection chemistry (liquid or solid, that is sodium hypochlorate or calcium hypochlorate) will elevate the pH (bleach is made by mixing chlorine gas, water and sodium hydroxide—and the pH of bleach is around 13). In this case let the well pump for perhaps 15-20 volumes and retest. 3) If, after this, the well is still high in pH, look to the water chemistry (what is alkalinity, hardness, etc.) for a cause. Then, look to treatment of the cause. Simply raising the pH may in itself have unexpected consequences.


Comments are closed.