More than I ever wanted to Know about bleach...

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Bones

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Feb 17, 2012
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Central Indiana
If I understand this right Cl ion is not subject to to degradation by UV radiation when attached to a CYA but yet it still remains as FC because its a weak bond. Cl ions are always looking for nitrogen to bond to so when not bonded to CYA on its bonds to a N and comes across a bad guy it attacks for lack of a better term and becomes a chloramine or breaks itself down. So knowing I want my FC at the high end due to all the stuff that will get into the pool and the kids me and the wife, 2 dogs etc, I want to run my FC at 7, from research it appears that 10ppm CYA protects 1.5ppm of FC so my optimum CYA would be 46.6 to protect my FC and not waste FC. I know levels will fluctuate so lets call it 50 ppm CYA which is close to what is recommend on the pool-school/recommended_levels chart. Now my pool will have lots of aeration(kids) direct sunlight from on average 9:00 am to 6:00pm, and lots of leaves bugs etc. So I expect FC usage to be higher than average, scratch that with this pool I already know it is. So it got me into this somehow...

But according to http://www.iwaponline.com/jwh/006/0513/0060513.pdf
If I wrapped my brain around this, I would want no more than about 30ppm of CYA to get maximum effective inactivation of cryptosporidium. I think....

So A maybe someone could explain a little better how hypochlorous acid actually kills bacteria, maybe why the ions attach to CYA, and how does superchlorination remove chloramines from the water, simple outgassing of the ammonia? Goes back to reading A New Kind Of Science, much simpler... than taking care of a pool...

after this ive been reading up on bromochloramine oxidation of N,N-diethyl-p-phenylenediamine(DPD) in the presence of monochloramines
 
I suggest you take a look at the post in the Pool Water Chemistry thread that shows the equilibrium equations. At the usual FC/CYA ratios, most of the chlorine is bound to CYA. Also see this post since the "rule" you quote about 10 ppm CYA protecting 1.5 ppm FC is just pure bunk so be careful about where you get your research.

It is not necessarily true that chlorine bound to CYA is not subject to any degradation from the UV of sunlight, but rather that it is far less likely to be degraded compared to chlorine that is not bound to CYA. Chlorine is able to react with chemicals other than those containing nitrogen, though mostly it reacts with certain nitrogen-containing compounds in typical pool and spa water. For example, chlorine reacts with ozone and with hydrogen peroxide, neither of which have any nitrogen.

If you have an FC that is roughly 10% of the CYA level, then the kill times are still fairly fast against the most common pathogens and in particular chlorine kills 99.9% of fecal bacteria in less than one minute as shown in the chart in this post. It's really only the protozoan oocyst Cryptosporidium parvum that cannot be killed by chlorine much at all, but that's true even with no CYA in the water and it is very unlikely you will have Crypto in your pool unless you or someone had diarrhea in the pool and were carrying Crypto. It isn't a pathogen just getting blown around in the air (like some algae spores) or carried in by most people (like fecal bacteria, skin bacteria, etc.). So while a concern in commercial/public pools where there are many strangers who share the water and not all are careful about staying out of the pool when they are sick, such concern isn't generally an issue for private residential pools.

As for the fate of chlorine when reacting with ammonia, that reaction and others (such as breakdown from sunlight) are described in this post where you can see that chlorine mostly oxidizes ammonia to nitrogen gas (there are side reactions that produce some nitrate and a very small amount of nitrogen trichloride -- some of these other reactions are described in this post).
 
Thanks you and the 10ppm,1.5ppm was more of a question, not a statement hence why i was asking. I had seen that figure quoted in a couple of places but never a government or accredited paper though. I appreciate all the information gives me a place to start studying.
 
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