On-site chlorine generation

[JoyfulNoise]

Just a thought bubble from me as I was thinking about this the other day. I wondered if the Stenner Pump owners here on TFP would be interested in an on-site chlorine generation technology such as this -

On-Site Generation, Sodium Hypochlorite Water Treatment | Products | MIOX

The above is just for illustration purposes although the company does offer their Rio-Zuni model which is capable of producing up to 2lbs of chlorine per day. There are other direct bleach production systems out there too, such as Chlorine Genie.

The only inputs, aside form electricity, are salt and a source of low CH water. My municipal water out of the tap would not be usable for a process like this so anyone with high CH water would likely need the additional step of a small, salt-based water softener to create the input water or a small-scale RO system. The above unit generates a mixed oxidizer chemistry (chlorine & peroxide) so it's not exactly a pure chlorine generator. One benefit of the mixed oxidizer process is that it eliminates (or reduces) the production of dangerous hydrogen gas at the expense of more pure chlorine production. I see no downside to the introduction of peroxide into the water as it will simply dissipate very quickly. The unit appears to have an ethernet port on the back which means integration with a remote controlled automation system is entirely possible.

It would be interesting to see a system like this in action. Honestly, if the price point were right, I'd consider direct chlorine (or "mixed oxidizer" injection) over an SWG system. One reason why a Stenner pump is not really an attractive option to me is that I don't want to lug bleach around and my outdoor temperatures are so high that bleach degradation would be an issue unless I moved the delivery system indoors or under cover. A direct generation and injection system eliminates those problems.

Again, just a thought bubble....

 

[pabeader]

Isn't peroxide used as a chlorine decreaser? Or am I missing something?

 

[JoyfulNoise]

Isn't peroxide used as a chlorine decreaser? Or am I missing something?

No, you have that right. My apologies for oversimplifying the chemistry issues. If you are willing to fork over your e-mail to that first website, you can access some of their technical information and there's a very good review article of on-site generated mixed-oxidant (MIOX) solutions. Essentially what is found is that these MIOX processes produce a solutions that has disinfecting properties that are different from what one would get if you simply mixed water and chlorine. In other words, a chlorine gas generated solution with an FC of 2ppm (forget about any effects of CYA for the moment) and a MIOX generated solution with an FC of 2ppm do not act the same way when one looks at ORP levels, pathogen kill times, etc. So the going theory is that the MIOX generated solutions have in them some mixture of chlorine gas (which will create the FC), chlorine dioxide (ClO2), ozone (O3), hydrogen peroxide (H2O2) and then a whole slew of other reactive radical species like hydroxyl radicals (OH^•), superoxide radicals (O₂^-•), hydroperoxyl radicals (HO₂^•), etc. Because of those extra oxidants, the solutions generated by MIOX are more "potent".

Now what does that mean for a pool? Well, I suspect the only thing that lasts is the chlorine and the rest of the oxidants will simply get used up by they time they make it out of the plumbing. So while there may be some prolonged contact time inside the plumbing, those oxidants will go away and the bulk pool water will simply be chlorinated pool water. Does that matter? Probably not. It would be like adding an ozonator to your pool - it'll add ozone to the water inside the plumbing but probably not affect the bulk of the pool water much.

 

[AUSpool]

When you say 'price point' I assume the smaller versions would work but I couldn't get any idea of the cost, any idea? There does seem to be a little more regular maintenance than the average SWG but its nice that they give that upfront.

 

[JoyfulNoise]

When you say 'price point' I assume the smaller versions would work but I couldn't get any idea of the cost, any idea? There does seem to be a little more regular maintenance than the average SWG but its nice that they give that upfront.

Yeah, I'm sure it costs a lot more than a standard SWG setup.

I was thinking that if one wanted to complicate the system even more, then one could generate the source water used to fill the brine tank with water from the pool. The way to do it would be to plumb a water line from the post-filter return side of the pool plumbing and then run that pool water through an active charcoal dechlorinating filter and a <5 micron fine particulate filter. Then use that filtered water to input into an reverse-osmosis (RO) cell (with an appropriately sized permeate pump to maximize the amount of RO water created). That RO filtered water can then be used to fill the brine tank since it would be free of most TDS. Then the MIOX generated water goes back into the pool.

In that setup, the only external source of water needed would be fill water for the pool since evaporative loss from the pool would be much greater than the waste water lost in the RO process. The only chemical input would be salt for the brine tank. The waste water from the RO filter would be discarded because it would be a combination of salt, calcium, CYA and any other minerals from the pool water. Salt would go into the pool from the MIOX process but a roughly equivalent amount would be removed by the RO process. So, on balance, the increase of salt over time in the pool should be minimal and only dictated by the fill water.

As for testing, all standard pool tests would still need to be performed but one would have to measure TDS (or at least try to calculate it) because most RO filters have a limit to the amount of CH and overall TDS allowed before damage to the membrane will occur. If one were to start off the pool with low CH fill water, keeping the TDS at manageable levels should be easy enough. The result would be chlorination of the pool with a much lower TDS burden....it would make all those Texas pool builders that hate SWGs now happy to warranty their stone work...

 

[Backyard_Lap_Pool]

When you say 'price point' I assume the smaller versions would work but I couldn't get any idea of the cost, any idea? There does seem to be a little more regular maintenance than the average SWG but its nice that they give that upfront.

I asked and it looks like the small 2# system is at a $10k price point and the 4# system is at a $13k price point. I couldn't get the math to work vs bulk sodium hypochlorite - as the break-even would be around 10 years - best case scenario (assuming negligible maintenance and repair costs for conversion cell.). Very intriguing product though! If they could get their price point down towards $4k-$5k, it would be a much easier cost to try to justify.


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[JoyfulNoise]

I asked and it looks like the small 2# system is at a $10k price point and the 4# system is at a $13k price point. I couldn't get the math to work vs bulk sodium hypochlorite - as the break-even would be around 10 years - best case scenario (assuming negligible maintenance and repair costs for conversion cell.). Very intriguing product though! If they could get their price point down towards $4k-$5k, it would be a much easier cost to try to justify.


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Thanks for looking into that!

Yeah, I kind of figured it was going to be an expensive setup. It really probably only makes sense in a commercial/public pool where storage of large quantities of liquid chlorine can be a problem. As I said in my original post, the Chlorine Genie is a residential scale system that basically pairs a simple salt-based water softener with an SWG to create a source of low CH, high FC water that can be added to a pool through a simple Venturi adapter on the return line.