Does chlorine oxidize ammonium

[bdare]

Does chlorine oxidize ammonium to nitrite and nitrite to nitrate or is this done by bacteria?

My only reference here is with aquariums where Nitrosomonas and Nitrosomonas bacteria do the oxidation. Don't know if chlorine would kill those bacteria or if they are still present in swimming pools.

 

[chem geek]

Chlorine will kill most bacteria very quickly as shown in the table in this post. For fecal bacteria, 99.9% are killed in less than a minute or two.

Chlorine reacts with ammonia to form monochloramine very quickly with 90% conversion in about one minute (with usual FC/CYA ratios as prescribed by this forum). It takes longer for chlorine to further oxidize monochloramine to end products where it takes around 4-1/2 hours for a 90% conversion (again, at usual FC/CYA ratios). The products with nitrogen at this point are 81.8% nitrogen gas, 8.5% nitrate, 7.9% monochloramine, 1.4% dichloramine, and 0.3% nitrogen trichloride. So you can see that chlorine oxidizes ammonia mostly to nitrogen gas and only to some nitrate (if you wait long enough, the chloramines will be fully oxidized). You won't find nitrite in swimming pools with chlorine because chlorine will quickly oxidize it to nitrate.

In practice, the chlorine oxidation of ammonia is continuous as the ammonia is introduced into the water. In a residential pool, the bather load is typically low so one normally doesn't see the chloramine intermediates. One person-hour of being in a swimming pool creates a chlorine demand of roughly 4 grams so if this were all from ammonia (and it's not) then in a smaller 7500 gallon pool this would be 0.14 mg/L (ppm) Combined Chlorine (CC). Most of the chlorine demand from bathers is not ammonia but urea and that is much slower to oxidize from chlorine taking days. The following table shows the chemicals with nitrogen (which are those which chlorine reacts with) in sweat and urine (the table is from this World Health Organization (WHO) document):

...................... Sweat ......... Urine
Compound . mg/L . % .... mg/L . %
Urea ............ 680 ... 68 ... 10,240 . 84
Ammonia ..... 180 ... 18 ........ 560 ... 5
Amino Acids ... 45 ..... 5 ........ 280 ... 2
Creatinine ....... 7 ...... 1 ....... 640 ... 5
Other ............ 80 ..... 8 ........ 500 ... 4
----------------------------------------------
TOTAL ......... 992 .. 100 ... 12,220 . 100

The typical discharge over an hour is around 200 ml of sweat and 50 ml of urine though this depends on the level of activity.

 

[bdare]

Cool!

Like I said all my water chem has been in fish tanks. I've only recently started maintaining a swimming pool so this information is very useful for me to draw correlations. In fish tanks I usually have to wait for anaerobic bacteria to turn nitrates into nitrogen gas.

I'm also happy to hear about chlorine killing fecal bacteria. From time to time my dogs will poo on the side of the pool. Every once in awhile some will fall to the bottom of the pool. Happy to hear I don't need to drain the pool when this happens...

 

[chem geek]

You do need to try and scoop out any formed stools since that's a lot of material for chlorine to handle. Also, there are some protozoan oocysts such as Cryptosporidium parvum that chlorine effectively does not handle. The data on whether the genotype of Crypto found in dogs is infectious to humans is unclear. Hopefully your dog does not have this disease. A primary reservoir for Crypto that can infect humans is in cattle as well as deer and mice (and of course humans themselves).

We generally recommend doing a SLAM (elevated chlorine levels) after a fecal accident just to be on the safe side and to accelerate the rate of disinfection.

 

[bdare]

You do need to try and scoop out any formed stools since that's a lot of material for chlorine to handle. Also, there are some protozoan oocysts such as Cryptosporidium parvum that chlorine effectively does not handle. The data on whether the genotype of Crypto found in dogs is infectious to humans is unclear. Hopefully your dog does not have this disease. A primary reservoir for Crypto that can infect humans is in cattle as well as deer and mice (and of course humans themselves).

We generally recommend doing a SLAM (elevated chlorine levels) after a fecal accident just to be on the safe side and to accelerate the rate of disinfection.

Thanks. I'll keep that in mind.

This is MUCH less of a problem in the summer when we actually use the pool because 1) I walk them more and 2) I clean up after them very regularly to avoid swimmers needing to dodge land mines while enjoying the pool.

Up until this week when my TFT-100 kit arrived I'd been relying on pool store tests. On my last visit 2 weeks ago my chlorine was at 10ppm. I'm assuming that is at SLAM levels?

I'll run some TFT tests tonight to verify.

 

[jblizzle]

You would assume incorrectly as the SLAM level is a function of your CYA level as shown in the FC/CYA Chart.

Here is the ShockLevelAndMAINTAIN Process. Have you read much of Pool School?

 

[bdare]

The typical discharge over an hour is around 200 ml of sweat and 50 ml of urine though this depends on the level of activity.

I'm assuming this doesn't take into consideration how much beer is being consumed?

- - - Updated - - -

You would assume incorrectly as the SLAM level is a function of your CYA level as shown in the FC/CYA Chart.

Here is the ShockLevelAndMAINTAIN Process. Have you read much of Pool School?

Got it. I will definitely SLAM the pool before I open it this spring.

I've actually done a ton of reading in pool school, but I didn't have the numbers memorized and was too lazy to go back and look it up while typing my last post.

 

[jblizzle]

No problem