When I first began designing water treatment (and water reuse) systems back in the 1970s, the primary method used to ensure that microbial populations were kept at bay was chlorination.  At least in the States.  Europe relied on ozonation.  (Think about this for a second- when so many of your population was killed by chlorine gas during war time, you have a hard time thinking it’s a good thing to use to render your water safe.)

There were plenty of problems with using chlorine.  First of all, it’s highly reactive- combining with so many chemicals to create carcinogens.  And, back when dialysis systems rarely fully treated their water, patient’s red blood cells lysed (blew up) on the spot.  (Chlorine oxidizes hemoglobin readily.)  Thankfully, adding ascorbic acid took care of that problem. (This idea was developed so long ago, there is no internet citation for : Ackerman, RA, Coles, JS. Effective reduction of chloramines levels in dialysate. Dial Transplant.1982;11:976–977.)   Not only did this work for dialysis, but ascorbic acid was added to streams to protect salmon from being killed by the chlorine.

We began using ultraviolet (UV) light and ozone ourselves for most of our projects.  Because these were inherently safer (and also oxidized away many of the recalcitrant organics still in the water). We even used UV light to treat fruit juices (the first non-pasteurized, shelf-life capable apple cider became available),  water-based medical products (and a slew of other non-water applications like coating beverage containers).   Of course, the problem with these choices is that there would be nothing left in the water to keep the microbial levels low, after application.  So, if the residence time is long between treatment and product use, there can be big problems.

Which is why the US Environmental Protection Agency decided to force a switch in the disinfectant choice to chloramine.  (OK, the EPA didn’t stipulate one had to use chloramine; just that by 1998, they wanted the chlorine byproducts in water eradicated. And, chloramine helped municipalities meet that standard.)  Chloramine already is a combined chlorine, one that is capable of killing microbes, but not as reactive with other compounds as is chlorine, which would create additional problems.  Chloramine persists longer (because it is already a combination product), but is not quite as potent as chlorine.

But, once you consider that you are killing microbial cells, it shouldn’t surprise you that there can be unintended circumstances.  Like the rashes some folks claim (without substantiation) or the respiratory problems some folks experience when they have been exposed to chloramines.  Or, the destruction of rubber gaskets.  And, it seems that there are, indeed, chemical combinations that chloramine can form- a whole slew of new disinfection byproducts.

Oh  This disinfection method can render the water more corrosive.- especially with lead pipes in the system (and with folks too cheap or too stupid to add phosphate to control the corrosion.)

Flint, Michigan, anyone?

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