Does Bromine react with Ammonia the same way Chlorine does?

[TreeFiter]

I'm just wondering if Bromine reacts in a similar way to chlorine when there is ammonia in the water. With chlorine, you need to add enough to use up the ammonia before you will be able to maintain a residual. Is the same true for Bromine? For that matter is there a Bromine equivalent to Chloramines?

 

[chem geek]

Yes and yes. Bromine combines with ammonia to form bromamine, but there is a difference in that bromamine is still an effective disinfectant unlike chloramine. Technically it's because not all the bromamine (NH₂Br) remains as such and instead forms a bromammmonium ion (NH₃Br⁺) that can have its bromine still be reactive. This is also why one doesn't separately test free and combined bromine in the test kit because the bromamine will test as free bromine so it's just called Total Bromine.

You get rid of bromamine the same way you get rid of chloramine, by adding more oxidizer to get rid of it.

 

[TreeFiter]

Thank you chem geek. Your response raises other questions for me. As I have recently gained an understanding of how Ammonia works in pools, I've started to notice things in hot tubs that I believe is the result of ammonia. It seems to make sense that there would regularly be ammonia in hot tubs considering the relatively small volume of water and the amount of bather waste being mixed in. So what I am seeing regularly is that if I add chlorine, usually dichlor grannular, the TC increases, but the FC remains at zero. Exactly what I would expect for a spa with ammonia. If I add more, eventually I will start to see FC. I also use MPS in these spas, and for the last few years, my routine has been to add MPS, adjust pH, add chlorine, and check and adjust pH again. Now I'm wondering if by adding MPS first, I'm essentially wasting it. Is the MPS being used up by the ammonia?

I'm thinking it makes more sense to add chlorine first, then MPS, then adjust pH. The only reason I was adding the MPS first was because with test strips, the MPS shows up as TC, and if there is already FC present, its very hard to tell if you have added enough MPS.

I should mention that some of these spas use a Nature 2 system, and others use Bromine tabs in a floater.

I will say that since I realized I was seeing ammonia, many of the spas that have been very difficult to maintain have stayed clean and clear, so I think I'm headed in a good direction.

 

[chem geek]

MPS doesn't react much with ammonia (unfortunately). The normal use of chlorine in a residential spa is to dose heavily enough after a soak to handle the bather load. You want to add enough chlorine after the soak such that you still have measurable FC 24 hours later. I've posted in other posts rough rule-of-thumbs for the amount of oxidizer needed based on person-hours of soaking.

Basically, you don't need to worry about ammonia. You just need to worry about adding enough oxidizer (usually chlorine) to handle the bather load.

 

[TreeFiter]

Isn't a significant part of that bather load urea, which is where the ammonia comes from? Your rule of thumb makes sense even if ammonia is present. If you have added enough to maintain measureable FC, you would have added enough to get rid of any ammonia.

Thanks again

 

[chem geek]

Though the largest nitrogenous component of sweat and urine is urea, that is not the same as ammonia. Chlorine that combines with urea will show up as Combined Chlorine (CC) but it is much lower to oxidize than ammonia though it does seem to break down significantly faster at higher temperature. My post in the Oxidation of urea thread shows how urea breaks down where chloramines are formed in the process and chlorine will further oxidize such chloramines.