Hi, sorry for my english.
I have been reading the thread, and the truth is very interesting, I am also very interested in building an autonomous system of salt chlorination, but I see that this thread was closed for a year, is there any electrical scheme to start a project?
many thanks


Moderator's note: This post and the first reply were split off from a thread on a related project at https://forum.allaboutcircuits.com/...e-generator-control-unit.142543/#post-1309984

 

..... A voltage applied to the plates in the cell causes an electro-chemical reaction which generates hypochlorous ions - to sanitize the water and oxidize bather waste.

hypochlorous ions (ClO-) never occur in the electrolysis of salt water.... chlorine and hydrogen gasses are given off and the salt slowly turns into sodium hydroxide ...

It's really not a good idea to sit in a bath of chlorine water , a very nasty WW1 gas which is absorbed through the skin ....

What about using UV or ozone to sanitize the water ?

 

The action of electrolysis also electrocutes the bugs.

 

The action of electrolysis also electrocutes the bugs.

I don't believe the water in the hot tube will be subject to electrolysis ... it would need to be salt water and it would slowly turn to caustic soda solution !! even worse for sitting in than chlorine water....

I imagine the electrolysis would occur in a small container and the gas released bubbled into the bath water ... very easy to achieve you can adjust the current right down to milli amps and leave it running continuously ... the chlorine will be continuously escaping from the bath water into the atmosphere ...

you need inert electrodes or the nascent chlorine will react and cause problems

 

hypochlorous ions (ClO-) never occur in the electrolysis of salt water.... chlorine and hydrogen gasses are given off and the salt slowly turns into sodium hydroxide ...

It's really not a good idea to sit in a bath of chlorine water , a very nasty WW1 gas which is absorbed through the skin ....

What about using UV or ozone to sanitize the water ?

What are you babbling about?!
The reaction at the anode is reduction of chloride ions to chlorine gas. At the cathode hydroxide ions and hydrogen gas are produced. There is no separator to keep these products apart and the dissolved chlorine very rapidly reacts with the hydroxide to produce hypochlorite. What happens to then depends heavily on the pH of the solution. If the pH is sufficiently low free chlorine will be produced. If it is sufficiently high hypochlorite persists. In quite a narrow pH range hypochlorous acid exists. See
www.hydroinstruments.com/files/Basic%20Chemistry%20of%20Chlorination.pdf

This process and equipment to produce it are extremely well established and extensively used. There are large systems for chlorination of municipal drinking water, intermediate for swimming pools, small drinking water systems using solar (photovoltaic) power and tiny ones that use a hand-cranked generator to produce the electricity.

In a brief search I didn't find anything useful on the actual physical design of the electrolysis cells or electrical system for small scale production.

 

Here is a link to details of a UK company that manufactures such products for small scale production:-

https://www.gaffey.co.uk/products/disinfection-systems

 

What are you babbling about?!
The reaction at the anode is reduction of chloride ions to chlorine gas. At the cathode hydroxide ions and hydrogen gas are produced. There is no separator to keep these products apart and the dissolved chlorine very rapidly reacts with the hydroxide to produce hypochlorite. What happens to then depends heavily on the pH of the solution. If the pH is sufficiently low free chlorine will be produced. If it is sufficiently high hypochlorite persists. In quite a narrow pH range hypochlorous acid exists. See
www.hydroinstruments.com/files/Basic%20Chemistry%20of%20Chlorination.pdf
In a brief search I didn't find anything useful on the actual physical design of the electrolysis cells or electrical system for small scale production.

No ...wrong ... the link you provided to support your case has nothing to do with electrolysis , but deals with the chemicals sodium and calcium hypochlorite , which of course create hypochlorous ions ....

There are dozens of you Youtubes dealing with this subject ...

hydrogen and chlorine are released ... the reaction you mentioned is so insignificant it can be ignored

As for the design of such a device a device ... just two inert electrodes in salt solution , what could be easier ???

 

There are probably millions of brine electrolysis chlorination generators in use worldwide. The city where I live converted all of the public swimming pools and hot tubs to this method over a decade ago. It is long established and widely used technology. [EDIT - the swimming pool chlorinators don't use concentrated brine but electrolyze salt at around 0.5% in the bulk water]

My link was specifically to show the sensitivity of the balance of gaseous chlorine, hypochlorous acid and sodium hypochlorite to pH, as illustrated by Figure 1.

 

moderate size commercial generator of sodium hypochlorite from concentrated brine
www.evoqua.com/en/about/.../WT-085.090.000-AU-PS-LR-OSEC-B-PAK.pdf

 

Does this explain why some public pools have water that is slightly salty?

 

Here is a link to details of a UK company that manufactures such products for small scale production:-

I see that company also offers chlorine dioxide generators. Chlorine dioxide is great fun - it has a nasty tendency to come apart with considerable vigor. Because of that it is "always" generated on site, but alas requires sodium chlorite if you want to use electrolysis to produce it. The big users, like pulp mills, make it from sodium chlorate - which is also a rather enthusiastic compound. Chlorine dioxide has the advantage over hypochlorite for water treatment and bleaching in that it works by oxidation without chlorination, so you don't get the chlorinated organic compounds like chloroform and carbon tetrachloride that hypochlorite produces. It is much better for disinfecting water with a lot of organic crude in it.

 

Does this explain why some public pools have water that is slightly salty?

Exactly. Unless it is something oddball, salt water pools are chlorinated by on-site electrolysis which is much safer for the pool staff than the older systems using bottled chlorine. They do have to add hydrochloric acid continuously to maintain the pH and essentially replace the chlorine that is lost to reaction with (things most people don't like to think about in their swimming pool water). The HCl reacts with excess NaOH to produce water and salt. Sodium hypochlorite solution (chlorine bleach) or calcium hypochlorite is sometimes used in salt pools when there is a need to quickly raise the chlorination level, such as when someone has committed an atrocity in the water.

I cycle by a swimming pool that has a back door with a sign on it that says CO2 Room - I presume this is an error, though the thought of swimming in carbonated water is rather intriguing.