Swimming Pool Help

[PoolBloke]

Hi

I realise this is not exactly homework…but I haven't formally taken chemistry class for about 45 years…so I may be a bit rusty.

I work in the swimming pool industry and I have realised over the last 4 years or so there is a big misunderstanding in the industry around CO₂ it is being blamed for runaway total alkalinity. I realised after thinking and my sketchy chemistry the issue is more likely hydroxide residual from sodium hypochlorite manufacturing.

To rectify this, I am writing an article, and it is heavy with chemical equations. That’s where I would like help.

I have attached the equations I have made, part from memory, part from bits and pieces on line and part from it simply makes sense ... to me anyway.

Equations.jpg (39.38 KiB) Viewed 954 times

As I said it is years since I did any chemistry, so I am likely to have unbalanced equations and other inconsistencies. I would appreciate the help in checking these.

It's more than possible some of these are incomplete as in missing part of the equation as it is how I think it is . I really appreciate the help.

[ChenBeier]

Equation
1.?? Dont understand what TA^2 * 10^pH -6.1 means
2. Correct
3 and 4. are the same , correct
5. Correct
6. Correct
7. Correct
8. Wrong where does the H comes from
9.correct
10. Wrong
11. Correct

Generally there is a equilibrium
H₂O + CO₂ <=> H₂CO₃ <=> H+ + HCO₃- <=> H+ + CO₃ 2-

So all reaction with CO₂ are the same with H₂CO₃ or the anions.

[PoolBloke]

Thanks.

Sorry the TA is total alkalinity. Assume bicarbonate ions as pH is usually less than 8.3.

I am arguing whether it was TA₂ or 2 by TA. Memory being a fickle thing. I saw this sometime somewhere in 1996.

Thanks

[PoolBloke]

Generally there is a equilibrium
H₂O + CO₂ <=> H₂CO₃ <=> H+ + HCO₃- <=> H+ + CO₃ 2-

So all reaction with CO₂ are the same with H₂CO₃ or the anions.

I get that. The industry doesnt.

The industry norm is CO₂ raises total alkalinity. Usually it rockets away. The industry blames the CO₂. Pseudoscience at its best. indeed on fitting CO₂ there will be a rapid rise in TA that needs acid correction to fix it. However it is not the CO₂ that causes it. The CO₂ shows an issue that is inherent in the pool chemistry specifically the chlor alkali manufacturing and use of hydroxide in sodium hypochlorite for elongating life. Normally it is hidden with acid pH correction so the reaction is not observed.

Anyway thanks for the help.

[ChenBeier]

TAC.
TAC ("Titre Alcalimètrique Complet" in French) also called Total Alkalinity or simply Alkalinity (Alk) is water content of bicarbonates (hydrogencarbonates. HCO₃-). carbonates (CO₃ 2-), free alkali (OH-), and positive ions associated with Ca 2+, Mg 2+, Na+ and K+

Note : "Titre Alcalimétrique simple" as TA (not used herein) measuring content of free water in alkali carbonates and alkali (Na+ associated with sodium and potassium K+). In natural waters TA can only occur si the pH is greater than or equal to 8.3 (TA = 0 si pH <= 8.3).
The distribution of constituent ions for alkalinity can be calculated from respective values of TA and TAC.