4 ms·

Hospital’s water purification system stripped out chlorine, killing 3 patients

12 points by carride 4y ago

gnicholas 4y ago
> the researchers noted that the two machines had been fitted with commercial water purification systems that included a 5.0-micron carbon filter (designed to improve taste and remove odors) and an ultraviolet disinfection unit. Both carbon filters and ultraviolet light are known to decrease chlorine concentrations. How does UV light decrease chlorine concentration?
- pixl97 4y ago
  https://www.wwdmag.com/disinfection/article/10918917/using-uv-for-dechlorination https://www.wwdmag.com/disinfection/article/10918917/using-u... >Between the wavelengths 180 and 400 nm, UV light produces photochemical reactions that dissociate free chlorine to form hydrochloric acid. The peak wavelengths for dissociation of free chlorine range from 180 to 200 nm, while the peak wavelengths for dissociation of chloramines (mono-, di- and tri-chloramine) range from 245 to 365 nm. Figure 1 shows the UV output of a high intensity Hanovia medium pressure UV lamp. Up to 5 ppm of chloramines can be successfully destroyed in a single pass through a UV reactor, and up to 15 ppm of free chlorine can be removed.
  - gnicholas 4y ago
    So it's not getting rid of chlorine, it's just getting rid of free chlorine? Is the hydrochloric acid better to have in the water than free chlorine? Or is it easier to filter out?
    - pixl97 4y ago
      What I don't know is how many PPM of free chlorine to what PH level of water you end up with, and I'm sure there's a number of factors there. But, from what I'm reading there are a number of acid resistant microbes that can survive in a low ph environment, so you have to bleach/chlorinate the systems at a regular level. https://www.avidityscience.com/media/wysiwyg/4230-MI4179_-_Drinking_Water_Acification.pdf https://www.avidityscience.com/media/wysiwyg/4230-MI4179_-_D...
    - gus_massa 4y ago
      It does not break the Chloride atoms. Chloride can form many molecules: One "family" is NaCl (table salt) , HCl (hydrochloric acid = muriatic acid), Cl-. They can kill bacterias when they are concentrated, but they are nor so powerful when diluted enough. Another "family" is Cl2 (chloride gas), NaClO (bleach[1]), HClO , ClO-. All of them are "free chloride" because they are essentially equivalent. If you ignore the Cl2 and compare the other 3 with the ones in the other family, the difference is that they have and additional oxygen. This oxygen can go out and "burn" a part of a bacteria, and enough "burns" will kill the bacteria. I'm not sure of the details, because I know chemistry but not too much, but from https://solar2000.co.za/wp-content/uploads/2019/11/Solar2000-article-Chlorine-consumption-by-UV.pdf https://solar2000.co.za/wp-content/uploads/2019/11/Solar2000... the idea is that there is always a small amount of innocuous contamination in water, and UV can make the bleach react with it. The reaction is something-H + HOCl (bleach) -> something-Cl+ HOH (water) The "contamination" exchanges one of it's hydrogens with a chlorine in the bleach, and the bleach is transformed into water. So the chorine atoms don't disappear, but now they are in a molecules that will not cuse "burns" to the bacterias. [1] It's more complicated, but let's call this bleach to simplify.
rolenthedeep 4y ago
The hospital installed water filters, a lack of free chlorine in the water allowed bacteria to grow in the ice machines. So really these patients died because the hospital didn't properly clean and maintain their ice machines.

12 points by carride 4y ago

> the researchers noted that the two machines had been fitted with commercial water purification systems that included a 5.0-micron carbon filter (designed to improve taste and remove odors) and an ultraviolet disinfection unit. Both carbon filters and ultraviolet light are known to decrease chlorine concentrations. How does UV light decrease chlorine concentration?

pixl97 4y ago
https://www.wwdmag.com/disinfection/article/10918917/using-uv-for-dechlorination https://www.wwdmag.com/disinfection/article/10918917/using-u... >Between the wavelengths 180 and 400 nm, UV light produces photochemical reactions that dissociate free chlorine to form hydrochloric acid. The peak wavelengths for dissociation of free chlorine range from 180 to 200 nm, while the peak wavelengths for dissociation of chloramines (mono-, di- and tri-chloramine) range from 245 to 365 nm. Figure 1 shows the UV output of a high intensity Hanovia medium pressure UV lamp. Up to 5 ppm of chloramines can be successfully destroyed in a single pass through a UV reactor, and up to 15 ppm of free chlorine can be removed.
- gnicholas 4y ago
  So it's not getting rid of chlorine, it's just getting rid of free chlorine? Is the hydrochloric acid better to have in the water than free chlorine? Or is it easier to filter out?
  - pixl97 4y ago
    What I don't know is how many PPM of free chlorine to what PH level of water you end up with, and I'm sure there's a number of factors there. But, from what I'm reading there are a number of acid resistant microbes that can survive in a low ph environment, so you have to bleach/chlorinate the systems at a regular level. https://www.avidityscience.com/media/wysiwyg/4230-MI4179_-_Drinking_Water_Acification.pdf https://www.avidityscience.com/media/wysiwyg/4230-MI4179_-_D...
  - gus_massa 4y ago
    It does not break the Chloride atoms. Chloride can form many molecules: One "family" is NaCl (table salt) , HCl (hydrochloric acid = muriatic acid), Cl-. They can kill bacterias when they are concentrated, but they are nor so powerful when diluted enough. Another "family" is Cl2 (chloride gas), NaClO (bleach[1]), HClO , ClO-. All of them are "free chloride" because they are essentially equivalent. If you ignore the Cl2 and compare the other 3 with the ones in the other family, the difference is that they have and additional oxygen. This oxygen can go out and "burn" a part of a bacteria, and enough "burns" will kill the bacteria. I'm not sure of the details, because I know chemistry but not too much, but from https://solar2000.co.za/wp-content/uploads/2019/11/Solar2000-article-Chlorine-consumption-by-UV.pdf https://solar2000.co.za/wp-content/uploads/2019/11/Solar2000... the idea is that there is always a small amount of innocuous contamination in water, and UV can make the bleach react with it. The reaction is something-H + HOCl (bleach) -> something-Cl+ HOH (water) The "contamination" exchanges one of it's hydrogens with a chlorine in the bleach, and the bleach is transformed into water. So the chorine atoms don't disappear, but now they are in a molecules that will not cuse "burns" to the bacterias. [1] It's more complicated, but let's call this bleach to simplify.

rolenthedeep 4y ago

The hospital installed water filters, a lack of free chlorine in the water allowed bacteria to grow in the ice machines. So really these patients died because the hospital didn't properly clean and maintain their ice machines.