The Problem with Chlorides and Chlorine

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My Problem with Chlorides and Chlorine

BY HYLAN JOSEPH

 

For a long-time I thought Godzilla lived on the moon with Rodan and King Ghidorah. Whenever I would watch Invasion of Astro-Monster, I would run outside with my binoculars and look at the moon hoping to see the fight. It was only until my neighbor, an actual rocket scientist, explained to me how wrong I was. This went on for years.

I make mistakes. I try not to repeat them, but I am human. After years in this business, studying water, taking organic chemistry in college, I am still not getting chlorides and chlorines. In the coffee tech world, we have patron saints — specific people who are experts in a specific area. The patron saint of water is Scott Manley. Scott was kind enough to give me a drubbing because I made the chloride & chlorine mistake several — 42 in total — times before. Scott is always there to help and is incredibly kind. With the well-deserved drubbing, Scott also produced a fine summary to help correct my problem with chlorides.

 

 

Correcting Hylan’s Problem with Chlorides and Chlorine

BY SCOTT MANLEY

 

FYI, we’re not talking about Chlorine and Chloramine; those are disinfectants, though you should test for them. Both of these are removed by carbon filtration and at the level present in drinking water isn’t going to cause an equipment problem if you are proactively changing filters. Meaning you don’t wait until the filter is failed, or you detect chlorine post-filter to change them; you change out the filters based on an expected water usage calculated against the filter capacity.

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Chloride is a dissolved solid. It’s when chlorine gains an electron. At ambient temperature and neutral pH, 316L stainless steel can handle quite a bit of chloride. Reverse osmosis (RO) membrane housings are often made of stainless and have no problem tolerating this, even at relatively high levels. It’s when you heat and pressurize the water that it becomes a problem, like in a sanitary boiler. That’s the challenge.

 

For the purposes of coffee, RO is the only reliable and predictable process for chloride removal. RO systems cannot tolerate any amount of chlorine, though. So, there’s the carbon filtration to remove the chlorine first, and then the RO removes the chloride. In an improperly installed or maintained RO system, the first thing to pass through the membrane (after H2O) is chloride. And an RO system with a blending valve returns chloride back into the product water. A good rule of thumb is that if the source water has a chloride concentration above 50ppm or the source water ion concentration is unstable (ala LA) you do not use blend back. Either way, if you are using blend back with chloride, you can no longer use a TDS meter to verify the product water – instead, you should test for chloride ion using the appropriate method.

Make sure that the RO system is in fact an RO and not a Nano filtration. Sometimes these are confused. Nano filtration does not remove monovalent ions such as chloride. Line pressure RO systems are sometimes actually just Nano filtration, either due to membrane selection or low net driven pressure.

 

Methods for testing chlorides in the field: 

  • QuanTab test strips – Hach – This is the same test strip that’s in the La Marzocco Water Kit. 

  • Manual titration – Hanna H13815 or Hach 8-P

  • Handheld meter – Hanna Checker – Note: This method only reads to 20ppm, but can read higher using dilution with distilled water up to 200ppm

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