Using Potassium Monopersulfate(KMPS) to reduce Combined Chlorine (CC)

[gbergeron]

I've been reading up on KMPS because I heard rumor that it can be used to reduce the overall CC by eliminating contaminates. I'm running into a few issues of how that works though and getting very little in the way of clarification from the articles I've been able to find.

What I am finding is this:
1) It appears as CC on a standard chlorine test; unless you have a special test or a way to neutralize it (but I can't seem to find what that is)
2) it is an oxidizer not a sanitizer.

Since I'm using chlorine as the sanitizing agent, will this really make a difference? Will raising the oxidizer in the water eliminate the contaminates that are causing a high CC?

The primary cause for my inquiry is that the 1,000 gallon public spa that I'm working on frequently runs high (1+ ppm of CC) and regulation says I have to shut it down to resolve that. The issue is that it is a 24 hour access pool and spa in a hotel and closing the spa nightly is unrealistic for our needs.

Will the use of KMPS prevent me from having to close the pool or spa (under normal circumstances) to maintain safe CC levels?

 

[JoyfulNoise]

1) It appears as CC on a standard chlorine test; unless you have a special test or a way to neutralize it (but I can't seem to find what that is)

What MPS shows up as depends on how you are testing. If you are using the DPD-FAS titration test, then it will show up as additional FC because some of the drops of the R-0871 reagent (FAS) will neutralize the MPS instead of converting the dye from it's pink form to clear form. Since you are using extra drops of R-0871, it counts towards FC. However, if you have no FC in the water (the sample is clear after adding the R-00870 powder), then it will show up as CC's on the DPD-FAS test.

If you are just using the DPD only test (pink color comparison), then the MPS shows up as additional CC's but not as FC.

If you want to eliminate the effects of MPS, then you need to purchase the additional reagents from Taylor for doing so.

2) it is an oxidizer not a sanitizer.

True. MPS is an oxidizer and has very little sanitizing capabilities. MPS is not any better than chlorine in terms of breaking down bather waste and, in some instances, is slower than chlorine. The only benefit to MPS is that is does not create the THM's that chlorine will.


You would be much better off if you could install some commercial-grade inline UV system to help destroy the bather waste. 1ppm CC's is quite high and can be very irritating in a hot spa.

 

[gbergeron]

You would be much better off if you could install some commercial-grade inline UV system to help destroy the bather waste. 1ppm CC's is quite high and can be very irritating in a hot spa.

Thanks for the insight, seems like MPS won't really do anything to solve the high CC levels based on the information in your response. At least it wouldn't be anymore effective than a breakpoint chlorination. Am I gathering that right?

The problem I'm running into is I can't seem to keep the CC levels below 1 ppm once people start using the spa. As I am only a maintenance tech at the hotel where the spa is I lack the authority to make changes to the system. I can recommend it to management but it's unlikely it'll get a green light from corporate. Given that it's meant to be 24 hour access and I can't alter the system layout, do you have any suggestions on how to manage the CC through chemical means?

 

[JoyfulNoise]

Thanks for the insight, seems like MPS won't really do anything to solve the high CC levels based on the information in your response. At least it wouldn't be anymore effective than a breakpoint chlorination. Am I gathering that right?

The problem I'm running into is I can't seem to keep the CC levels below 1 ppm once people start using the spa. As I am only a maintenance tech at the hotel where the spa is I lack the authority to make changes to the system. I can recommend it to management but it's unlikely it'll get a green light from corporate. Given that it's meant to be 24 hour access and I can't alter the system layout, do you have any suggestions on how to manage the CC through chemical means?

Elevated CCs are always going to be a problem because you are using chlorine as a sanitizer/oxidizer, you have high bather loads and the spa is given no time to recover. Even the most expensive and complex water parks often shut down rides and pools for a few hours everyday so that technicians can treat the water appropriately and make it safe to swim in. If your management is tying your hands on this, then it's their fault for poor water quality and customer complaints. You should go back to your management and sit down with them and explain that the spa needs to be taken offline for a few hours everyday to allow the water to recover and for the CCs to be treated as you simply can not run a hot tub with sweaty, smelly diseased people in it all day long and expect to have anything approaching safe bathing conditions. It would not surprise me in the least if your pipes and filtration system was full of biofilms and bacterial colonies simply because the water is never allowed to recover.

Once you can build some decent recovery time into the spas schedule, then you can start playing with chemical treatment methods. Using MPS is not out of the question given how heavily used the spa is. In fact, it's really your only option for a non-chlorine method of oxidation. The problem is measuring it to make sure you can dose the water effectively, and that requires a better test kit. A UV disinfection system would be the best way to go and, instead of looking at it as something that adds cost, your management should see it as an investment in the operational efficiency of the spa. They want this thing to be open 24 hours a day, right? So if that's what they want, then they need to invest in the right equipment to make that happen. It's short-sighted and, to be blunt, stupid to think that you can do this kind of stuff on the cheap. Believe me, all it takes is for one outbreak of legionella or, less dramatically, a bunch of people getting pseudomonis (aka, hot tub rash) before the health department comes in and shuts down the spa completely until an even more costly remediation is done.

Unfortunately you are stuck between a rock and hard place but that doesn't mean you should compromise on what you think is the right approach just because someone in a suit only cares about the bottom line....

SO, to bring this back to something constructive -

1. The hot tub has to be shutdown for at least 4-6 hours per day to recover - have the brainiac manager go over the records and figure out when the least disruptive time of the day that is (maybe 12am-6am or there about).

2. Get a test kit with reagents that allows you test for MPS

3. Use a combination of MPS and chlorine in the off-hours to try to bring the CCs down to a manageable level. This will require some trial and error to figure out.

While doing all that, keep an eye on pH and TA to ensure that your water remains comfortable.