Useful CYA conversion to ammonia?

[JesseWV]

I noticed there have been quite a few cases this season where all the CYA was converted to ammonia. I've read that this happens because of a bacteria found in soil consumes it and releases ammonia as waste.

In the cases we see, this is always bad. Usually resulting in high chlorine demand to get rid of the ammonia and the need to add CYA again back to recommended levels.

Today it occurred to me...

Could this be used to convert only a fraction of the CYA in pools with levels >100 and stopped at a desired level?

We would need to:
Identify the bacteria strain, culture it, and keep it alive in storage in measured quantities
Calculate correct dosage concentration per gallon
Calculate/measure CYA consumption rates
Measure ammonia ppm per ppm CYA consumed

Steps could be:
Reduce FC to 0 with thiosulfate
Add calculated bacteria dosage
Measure ammonia until calculated concentration is reached
Stop consumption event with SLAM process to kill bacteria and break down ammonia.

The question is: Will the cost of the bacteria and chlorine be more than the cost of fresh fill water.

 

[JVTrain]

I'm willing to donate samples!

It's an interesting idea. There are no practical methods to removing or reducing CYA that I've heard of and this might be an approach to look into developing. Most of the work would be isolating the proper bacteria that is consuming CYA and the conditions under which it does.

 

[JasonLion]

Best of luck with identifying the bacteria strain, culturing it, and keeping it alive in storage. And don't forget that you also need to identify the water conditions that support bacterial consumption of chlorine.

There certainly are regions of the country where water usage is restricted and it would be worth a fir bit of money to get this working.

 

[Smykowski]

I think a better first question is to understand the process first. Why do some pools have the conversion happen over summer, and what factors trigger it?

Poor chemistry? Environment where the pool resides?

 

[duraleigh]

Even being retired with some time, I couldn't fathom how to begin that project.

 

[chem geek]

As noted in the thread Degradation of Cyanuric Acid (CYA), the CYA does not need to get converted only to ammonia. Depending on conditions, the ammonia can get converted to nitrogen gas and/or nitrate. Ideally, one would have soil bacteria convert CYA into ammonia and then have nitrification from Nitrosomonas bacteria to convert the ammonia to nitrite and then have annamox bacteria convert ammonia and nitrite to nitrogen gas (or after nitrification, have further nitrification from Nitrobacter bacteria convert nitrite to nitrate and then have denitrifying bacteria such as Pseudomonas aeruginosa convert nitrate to nitrogen gas). By going all the way to nitrogen gas or to nitrate, one avoids having a huge chlorine demand.

Since for every ppm of CYA it takes roughly 3 ppm FC to get rid of the ammonia if it stops there, this is a HUGE chlorine demand that is usually not very economical to get rid of if one starts with high CYA levels. Water replacement is often cheaper. This is why it would be better to go all the way to nitrogen gas and avoid the chlorine demand altogether.

Not all CYA losses over the winter result in huge chlorine demand and it is possible that some of this may be due to conversion of CYA into nitrogen gas or nitrate. Of course, some CYA loss occurs from dilution with winter rains, but there are quite a few pools that have a complete CYA loss yet do not show large chlorine demand upon opening.

Managing such bacteria is difficult, though is what is done in bio-reactors for creating some types of drugs and other chemicals and is what is done in some water treatment plants for breaking down chemicals in sludge. It's not something you can readily do in a residential pool.

 

[AimeeH]

I also have noticed an increase in these threads this year. Didn't happen to me. I let pool go green over winter (we do not winterize but run pump a few hours a day with thermostat to kick on when near freezing). I opened to a cya of about 40-45 with 0 chlorine (SWG).

What I'm wondering is if there is an identifiable common factor to CYA converting to ammonia. I've noticed it "seems" to happen in both instances of mild to extreme winter conditions.

 

[Smykowski]

In my nonscientific observations, it seems to be inground pools that are closed up and the FC gets down to zero for a substantial amount of time. I would be interested to know, of the people who are dealing with ammonia this spring, what procedure did they use to close last fall?

 

[chem geek]

As I noted in the thread It Can Happen to Anyone - Zero Chlorine, CYA-->Ammonia, it doesn't take very long for such a conversion to occur, at least when the water is warm and full of nutrients (phosphates and probably nitrates). It literally happened in just a few days in my pool, but still had a huge chlorine demand.

Just like algae, bacteria need essential nutrients such as phosphates and nitrates and they grow more quickly in warmer temperatures. So over the winter such conversion would be a slower process and just like algae growth it's more likely to occur or at least to occur more quickly during spring opening as the water is warming up.

It generally happens when the FC gets to 0 which is the case for pools that are winterized. In my pool I maintained FC, but when the solar came on I didn't account for the increase in chlorine demand from junk in the panels so the FC went to 0 and voilà a bio-reactor was born.

I don't think there are that many more conversions this year than before. We pretty much say that most years, roughly in proportion to our growing membership. There are quite a few pools that lose CYA without the chlorine demand and others that have such demand. Other than maintaining an FC level over the winter and minimizing risk by closing and opening while the water is cool, the only other thing one can do is to remove nutrients from the water. It's similar to preventing algae growth except that bacteria reproduce more rapidly and are more easily killed by chlorine.

 

[Casey]

My old pool always used up the CYA over the winter. I figured I'd see the same thing in my new pool, 15 miles from the other pool location... I lost 10ppm CYA and tested at 40ppm upon opening this year. As far as I could tell, I did everything the same. I've never dealt with a build up of ammonia though.

 

[JasonLion]

The ammonia can outgas, i.e. go away, but we don't know why it does sometimes and not other times.

 

[Pool_Fool]

I have come across two pools with what I believe this has happened. One pool, that was tested at 80ppm of CYA in the fall, was at zero in the spring.
The second I am not sure of the fall readings(new client), had a reading of 60ppm this spring. I was thinking to be proud of them until the first slam went
to .5 FC and 3.5 CC. I would have to attirbute that to a CYA breakdown.
The first pool was closed with a solid cover and the second a trampoline cover. Opposite sides of town.
(neither pool I was involved in the closing efforts)