Monopersulfate PPM recommendations

[Sean1]

Hi,
I am now testing for Monopersulfate to separate out Total Oxidizer from Chlorine. I have searched the web and can not find any recommendations PPM for Monopersulfate.

Also I understand from various reading that monopersulfate does not actually act to break down Combined Chlorine, but rather acts to prevent it's formation. This is a different story than I normally see and seems counter to my experience. I have been unable to find the chemical reactions explained anywhere to confirm how MPS interacts to do its job.

Your advice and insight on both of these topics would be very useful.

Thanks

Sean

 

[justinc]

Hi Sean,

Not to change the subject or try and tell you to do things differently, but do you have a particular reason you are using MPS instead of chlorine?

 

[CarolineM]

This sounds like one for @JoyfulNoise

 

[Sean1]

Hi Sean,

Not to change the subject or try and tell you to do things differently, but do you have a particular reason you are using MPS instead of chlorine?

Well actually a great question. I do an event in a 7500 gallon above ground pool. New showered bodies at a pretty high rate. If CCL or CL gets away from me then have to raise chlorine and wait. Assuming MPS reduces CL load (for the things MPS can oxidize) and also reduces CCL formation then I have to wait with an empty pool less often.

 

[justinc]

If this "event" is a pool party, my strategy is usually to raise free chlorine several ppm above normal (but not close to shock levels) prior to and after the party while running the pump constantly... and it has never caused any issues after very large parties and I have never had anyone complain about the water.

I am not sure if you are doing something else where you say you have large numbers of people in and out of the pool constantly where this type of strategy would not work?

Or are you doing a "weekly shock" and wanting to avoid the 12-24 hour downtime around that time while the chlorine levels are raised? If you maintain your chlorine and CYA levels appropriately, you won't ever have to "shock" your pool on a routine basis.

On this forum, MPS typically is avoided because it will interfere with the combined chlorine reading of a DPD test. There are ways to counteract this by buying an additional reagent from Taylor for your testing kit, but there aren't really many advantages of using MPS over chlorine in routine instances to make this an attractive option. MPS does not sanitize (as you already know) and only oxidizes (so there's another disadvantage).

However, as you mentioned, MPS does comes with the purported benefit of being able to swim soon or immediately after adding. So... if you had to absolutely have constant use of a pool with no downtime during a specific period and had to shock because of elevated combined chlorine, I guess you could theoretically use MPS and manage accordingly with the additional testing procedures from Taylor... And in this case, your recommended dose is 2 lb per 10,000 gallons (or for 7500 gallons, 1.5 lb).

You don't need to test MPS levels in the water as you aren't looking for any sort of residual MPS level. What you are looking for is chlorine levels within acceptable ranges for your CYA as well as combined chlorine levels of less than 0.5ppm. If you are dosing appropriately and have little to 0 combined chlorine and plenty of free chlorine then you know you have hit the right "ppm" (as you ask) for your particular situation.

By asking someone to calculate how much MPS it will take to oxidize everything is like asking us to look at a picture of a pool and know how many gallons of bleach it will take to SLAM.

You dose the pool appropriately, and test the chlorine and combined chlorine to ensure that the water has been cleared of chloramines and the pool has a sufficient free chlorine residual for future/ongoing sanitation and oxidation.

 

[JoyfulNoise]

MPS, also known by its trade name Oxone, is a type of persulfate oxidizer. It has the following half cell redox reaction -

HSO5− + 2 H+ + 2 e− → HSO4− + H2O , E = +1.81 V

Essentially the persulfate (HSO5 -) strips two electrons from whatever it reacts with and combines with 2 hydrogen ions to form bisulfate and water. The bisulfate goes on to lower pH which is why MPS can be acidic. Compared to chlorine (E = +1.7 V) it is a slightly better oxidizer. Persulfates will more easily attack carbon-hydrogen bonds and carbon-oxygen bonds rather that carbon-nitrogen bonds or nitrogen-nitrogen bonds.

Strong oxidizers like MPS, ozone and peroxide typically interact with chloramines by being radicalized - UV light or trace metals like Fe can form oxidizer radicals (Cl, hydroxyl, sulfate and oxygen species). Radicals are highly reactive, short lived (transient) chemical species that can split apart even the most chemically inert organic compounds. There are multitudes of different reactions that can occur so it’s really not easy to pinpoint one and say, “that’s it!”

Generally you want MPS to react with organics and oxidize them as much as possible before raising chlorine levels. This ensures that chlorine can be more effective at doing its job. The problem is that, in practice, it’s very hard to segregate chemical reactions in a pool so just dumping a bunch of different oxidizers in the water can have some very unwanted results.

 

[Sean1]

MPS, also known by its trade name Oxone, is a type of persulfate oxidizer. It has the following half cell redox reaction -

HSO5− + 2 H+ + 2 e− → HSO4− + H2O , E = +1.81 V

Essentially the persulfate (HSO5 -) strips two electrons from whatever it reacts with and combines with 2 hydrogen ions to form bisulfate and water. The bisulfate goes on to lower pH which is why MPS can be acidic. Compared to chlorine (E = +1.7 V) it is a slightly better oxidizer. Persulfates will more easily attack carbon-hydrogen bonds and carbon-oxygen bonds rather that carbon-nitrogen bonds or nitrogen-nitrogen bonds.

Strong oxidizers like MPS, ozone and peroxide typically interact with chloramines by being radicalized - UV light or trace metals like Fe can form oxidizer radicals (Cl, hydroxyl, sulfate and oxygen species). Radicals are highly reactive, short lived (transient) chemical species that can split apart even the most chemically inert organic compounds. There are multitudes of different reactions that can occur so it’s really not easy to pinpoint one and say, “that’s it!”

Generally you want MPS to react with organics and oxidize them as much as possible before raising chlorine levels. This ensures that chlorine can be more effective at doing its job. The problem is that, in practice, it’s very hard to segregate chemical reactions in a pool so just dumping a bunch of different oxidizers in the water can have some very unwanted results.

This is a great answer. Thank you so much. From what you have said and what I have read, using MPS to act as an additional oxidizer, can help the chlorine be more available to do its job. (I understand that MPS does not kill bacteria/viruses, etc). That said it takes more complex testing to separate out the Chlorine PPM from the MPS PPM. You also mentioned that having multiple oxidizers in the water can create some unwanted results. Would you be willing to explain that more? I understand from a previous reply that at least a few folks have negative reaction to MPS and I am trying to understand if it is just a complexity of using it correctly issue, or if there is something more intrinsic.

 

[gorocket1981]

When I bought this non chlorine shock last year following the recommendation and good comments of the pool store, I left the store with the impression that it was a revolutionary product to have the pool shocked and to maintain clarity and sparkle of the pool.

After reading comments in this thread and some others thread that talk about this, it seems that it is not good at all. So another useless expense?

 

[mknauss]

So another useless expense?

Correct.