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Thread: Killing pathogens?

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    Killing pathogens?

    So, hypochlorous acid and ozone are able to breach the cell walls of pathogens, but potassium monopersulfate cannot?

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    Re: Alternative sanitizers and "chemical free" pools--The Truth!

    No, potassium monopersulfate is an oxidizer and also kills pathogens but too slowly to be able to pass EPA DIS/TSS-12. There is an exception which is the use of silver ions with MPS at hot spa temperatures which does kill quickly enough to pass these EPA tests and is the basis for approval of the Nature2 system for spas. The chemistry of why silver ions with MPS at hot temperatures is a disinfectant is described in this post where silver ion and persulfate ion combine to form sulfate ion radicals and divalent silver ion.
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    Re: Alternative sanitizers and "chemical free" pools--The Truth!

    It seems that Chlorine sanitizes by oxidizing living microorganisms quickly.

    Potassium Monopersulfate tries to sanitize by oxidizing living microorganisms, but it can't do it quickly enough.

    Colloidal Silver doesn't oxidize anything, but somehow it can kill living microorganisms, but it can't do it quickly enough.

    I'm confused.

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    Re: Killing pathogens?

    The actual chemistry of what happens is far more complex than what you describe. We try not to get into too much detail here on this forum except in The Deep End. Chlorine doesn't just kill organisms by oxidation of certain chemicals and that isn't the initial way that most pathogens get killed. The chlorine can also kill them by attaching to critical molecules usually in a substitution reaction where it replaces a hydrogen attached to a nitrogen (in an amine). This then makes some protein chemicals not work properly anymore usually by causing them to either unfold or to clump together (depending on the protein and where it is attacked). The microorganism then goes into a shock similar to what happens when you apply too much heat since that also disrupts protein chemistry. This article talks about how bleach kills bacteria (you can read this paper for even more details).

    MPS is a more selective oxidizer in some ways and it doesn't do the substitution reaction so tends to cause less havoc inside cells. Of course, everything is concentration dependent, but I'm talking about the usual ppm concentrations used for these chemicals.

    Silver kills bacteria not through oxidation reactions but by binding to sulfur in proteins preventing them from folding properly. Silver also interferes with iron metabolism since iron is bound in some reactions by sulfur. This article talks about the process (this paper goes into more detail). However, metal ions such as copper and silver, do not kill as quickly as chlorine for most pathogens. This is described in this post where you can see that silver ions kill fecal bacteria around 50 or more times as slowly as chlorine whereas copper ions don't kill such bacteria at all (again, at pool concentrations) because such bacteria live in the G.I. tract that is exposed to bodily fluids that already contain copper so these organisms have mechanisms for removing or sequestering copper to prevent it from damaging them. Copper is better at inhibiting algae growth because the algae don't have copper-resistant mechanisms like fecal bacteria and algae reproduce more slowly so the slow killing isn't as problematic.

    The silver ions with MPS at hot temperatures are different since they create sulfate free radicals and these are more destructive. Also, the created divalent silver ions are likewise more potent than regular silver ions.

    We don't recommend the use of metal ions because of their risk of staining, especially for plaster surfaces.
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    Re: Killing pathogens?

    Moved to The Deep End.
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    Re: Killing pathogens?

    So, Potassium Monopersulfate doesn't have the special killing abilities that Chlorine and Bromine do.

    But, given enough concentration, even Potassium Monopersulfate could be a sanitizer? Kind of like bringing down a tree with a wrecking ball? Whereas chlorine or bromine are like bringing down a tree with a chainsaw?

    Copper and Silver seem to be very selective in what they kill.

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    Re: Killing pathogens?

    I wouldn't put it that way. MPS does kill pathogens, but more slowly. It's somewhere in between chlorine/bromine and copper/silver. There's not a line where something is special and something else is not. It's more of a range based on modes of action and on speed.

    Yes, given higher concentrations, most of these chemicals can kill pathogens. Generally speaking, if they can kill them at all even slowly, then a higher concentration kills them faster.

    And yes, copper and silver are more selective in what they kill for several reasons. One is that they don't interfere with as many chemical processes and another is that they are not oxidizers. So they are generally ineffective against viruses because viruses aren't reproducing until they get into a host. With chlorine and to a lesser (slower) extent with MPS, they oxidize some chemicals so can inactivate viruses and some protozoan oocysts outside their host.
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    Re: Killing pathogens?

    Thanks for the explanation.

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