Indoor Pool Trichloramines Questions

[superdave5599]

Question based on some comments in the Swimming Reddit forum. I had said that well-maintained water shouldn't ever need to be changed. One person said that trichloramines forming was the reason the water did need to be changed periodically. That there was no other way to get rid of them. I had latched onto their original assertation that "if the water is salty tasting and it isn't a salt-water pool, that means it hasn't been changed recently" implying it wasn't maintained well. I had repeated what I read here-that chlorine will add salt and therefore the salt taste could just be a sign that the pool has been chlorinated for a long time.

So I got interested and did some googling... Found some different sites suggesting that superchlorinating, AKA shocking at roughly 10 times the amount of chloramines would get rid of chloramines. However, I found another that stated that there are three types that get formed, depending on what exactly the chlorine was reacting with: chloramines, dichloramines, and trichloramines and the shock procedure doesn't get rid of all of them-leaving trichloramines behind.

I also found some research looking at how trichloramines can cause asthma-like problems in lifeguards and professional-level swimmers (i.e. people who are in the building for a long time breathing them in. Those research papers also referred to the trichloramines as being volatile fumes-I couldn't find anything about them being in the water itself for long. Suggestion in those papers was improved and strategic ventilation.

So my question for those in the deep end:
How does one get rid of chloramines in an indoor pool in general?
Am I correct in my understanding that the trichloramines are volatile and will off-gas into the air quickly, so it is the air that needs to be changed out regularly, not the water?
Do trichloramines cause any health effects while still present in the water, prior to off-gassing?

 

[JoyfulNoise]

Feel free to read through these two threads -

Post in thread 'Breakpoint Chlorination'
Breakpoint Chlorination

Thread 'Chloramines and FC/CYA'
Chloramines and FC/CYA

So my question for those in the deep end:
How does one get rid of chloramines in an indoor pool in general?
Am I correct in my understanding that the trichloramines are volatile and will off-gas into the air quickly, so it is the air that needs to be changed out regularly, not the water?
Do trichloramines cause any health effects while still present in the water, prior to off-gassing?

Chloramines of all kinds are best removed by UV oxidation. This is why outdoor pools often have very low concentrations of CCs and why some on TFP recommend installing a UV sterilizer units to indoor pools.

Trichloramine, NCl3, is the most volatile, reactive, and irritating of the simple chloramines. It has very low solubility in water and mostly outgasses at pool temperatures. Ventilation is the most important aspect of indoor pool air quality.

Very little trichloramine remains dissolved in water. Any small concentration that does can be irritating but it’s highly unlikely.

 

[JamesW]

Indoor commercial high use pools are very difficult to manage and it requires a professional commercial system designed to manage a variety of waste products that can accumulate due to swimmer waste.

Chlorine alone cannot handle an indoor commercial high use pool.

The contaminants are typically nitrogen based and/or carbon based.

Carbon based molecules are referred to as organic and nitrogen based molecules are referred to as inorganic.

UV is one way to deal with the contaminants.

There are relatively few professional companies who know how to effectively deal with large amounts of contaminants introduced by high bather loads.

The cost to install and operate a proper professional commercial setup is high and most commercial pools try to avoid the cost and they try to use chlorine alone with usually poor results.

 

[JamesW]

The simplest nitrogen based contaminant is ammonia.

Ammonia is NH₃ or NH₄⁺.

The hydrogen atoms are +1 and chlorine is also +1 so the chlorine can substitute for one, two or three hydrogen atoms to create Monochloramine, dichloramine or trichloramine (aka nitrogen trichloride).

The simplest carbon based contaminant is Methane.

Methane is CH₄.

The hydrogen atoms are +1 and chlorine is also +1 so the chlorine can substitute for the hydrogen atoms to create products like trihalomethane (CHCl₃ aka chloroform).

Note: The term "halo" in trihalomethane refers to halogen, which can be chlorine, bromine, iodine, fluorine etc.

So, CHCl₃ aka chloroform is a type of trihalomethane called trichloromethane.








The chlorine can eventually oxidize the nitrogen or carbon to create nitrogen gas or carbon dioxide, but that takes a long time and the disinfection byproducts can persist at unhealthy levels especially if the pool is high use where the contaminants are being introduced faster than the chlorine can oxidize the nitrogen and carbon atoms.

UV helps by being a catalyst, which speeds up the oxidation by providing energy to make the reaction happen.

Ozone can be used, but it cannot be just pumped into the return lines because that is not effective and you do not want ozone being released into the indoor space where people are.

Ozone needs contact tanks and a degass vessel to provide adequate contact and then you degass and destroy the ozone.

 

[JamesW]

Many pools use dilution to help manage contaminant levels and they regularly replace a lot of water on a regular basis.

If they have sand filters, they might backwash a lot and this replaces a lot of water.

There are also other types of treatments that can help address contaminants like Granular Activated Carbon, Reverse Osmosis and other types of filtering to remove contaminants.

 

[JamesW]

Humans sweat and pee while they are in the water and this provides products like Urea, Uric Acid, Creatine, Ammonia/ammonium etc.

These products contain carbon, nitrogen and hydrogen atoms.

Chlorine combines with these usually by replacing the hydrogen atoms.

As the molecules break down, they form simpler molecules.

This creates persistent DPBs (Disinfection Byproducts).

The components of sweat include water, urea, salt, and acids.

Human urine is composed primarily of water (95%).

The rest is urea (2%), creatinine (0.1%), uric acid (0.03%), chloride, sodium, potassium, sulphate, ammonium, phosphate and other ions and molecules in lesser amounts.

Disinfection by-products (DBPs) are formed when disinfectants like chlorine interact with natural organic materials in water, such as in chlorinated drinking water and chlorine-treated swimming pools.

DBPs can be found in the air during activities such as showering, bathing, dishwashing, and swimming.

The most common type of DBPs are trihalomethanes (THMs).

Disinfection By-products (DBPs) Factsheet | National Biomonitoring Program | CDC

CDC’s Division of Laboratory Sciences coordinates the National Biomonitoring Program (NBP) which offers an assessment of nutritional status and the exposure of the U.S. population to environmental chemicals and toxic substances.

www.cdc.gov

 

[JamesW]

Nitrogen trichloride is what causes the explosion when you mix trichlor or dichlor with calcium hypochlorite.

Nitrogen trichloride is a nasty, stinky, corrosive and explosive gas.

Many people think that chlorine gas is produced when you mix ammonia and bleach, but the product produced is trichloramine aka nitrogen trichloride.

2NH₄⁺ + 3OCl^- + 3HOCl + H⁺ <--> 2NCl₃ + 6H₂O.

Nitrogen trichloride is a chlorinated gas, but it is not chlorine gas.

Nitrogen trichloride is very similar to chlorine gas because it is very reactive and corrosive and the pH is very low on contact with water.

2Cl₂ + 2H₂O --> OCl^- + HOCl + 2Cl^- + 3H⁺

2NCl₃ + 6H₂O <--> 2NH₄⁺ + 3OCl^- + 3HOCl + H⁺.

For pools, most of the ammonia will be Ammonium NH₄⁺.

 

[DavidLast]

What sort of pool is this commercial or domestic?

What sort of bathing loads is it subject too?

Looking at the water test results following a heavy days use the day before what are the free and total chlorine readings?