water treatment technologies

[dfopiso]

hello to all,

we are still using chlorine in swimming pool application, but are moving to environment-friendly and lower cost options, such as:
1. ozone generator
2. chlorine dioxide

your comments pls in these 2 options.

thanks,
dave.

 

[coloeng]

What exactly are your concerns with chlorine?

I'm not really familiar with disinfection for a pool. For most water treatment systems, however,chlorine is typically the least expensive method of disinfection. The biggest issue right now with gaseous chlorine is the safety aspect. It can become more expensive if a retrofit for a chlorine scrubber has to be done.

From a cost stand point, ozone and chlorine dioxide are about equally more expensive than gaseous chlorine because of the up front capital costs. Ozone requires a lot of electricity to generate and so it has higher operating costs.

Chlorine dioxide has the advantage of being safer than gaseous chlorine while stilling being able to maintain a chlorine residual in the water.

Ozone is probably better at disinfection, in that it is more effective against protozoa type organisms. One drawback to ozone is that there is no residual. This means that in a water system you still have to add chlorine to the water so that there is a disinfectant residual in the distribution system.

Hope this helps.

 

[dfopiso]

hello coloeng,

---------------
What exactly are your concerns with chlorine?
---------------

from reading materials of suppliers, "Chlorine in water converts to a large percentage as chloramines. by heat and air agitation, chloramines convert to chloroform, a toxic carcinogen. other by-product of Chlorine in water is trihalomethanes (THM)".

any of this claim to be true?

you are correct that ozone gen consumes high kwh.

thanks,
dave.

 

[bimr]

No, it is not true.

Chlorine reacts with ammonia that is present, the end product is chloramines. If you add more chlorine, you will oxidize the chloramines (and ammonia) and you will end up with free chlorine. Free chlorine does not sting and burn the eyes like chloramines do.

If you keep your pool water clean, the generation of chlorine disinfectant byproducts will be reduced.

Chlorine dioxide is considerably more difficult to use in swimming pools. Ozone has no residual disinfecting power, so it has limited use in a swimming pool.

"Can chlorine dioxide be used to disinfect swimming pools?
For swimming pool disinfection the combination of chlorine (Cl2) and chlorine dioxide (ClO2) can be applied. Chlorine dioxide is added to the water. Chlorine is already present in the water as hypochlorous acid (HOCl) and hypochlorite ions (OCl-). Chlorine dioxide breaks down substances, such as phenols. The advantages of chlorine dioxide are that it can be used at low concentrations to disinfect water, that it hardly reacts with organic matter, and that little disinfection byproducts are formed."


"What are the costs of chlorine dioxide use?
Chlorine dioxide is about 5 to 10 times more expensive than chlorine. Chlorine dioxide is usually made on site. The costs of chlorine dioxide depend upon the price of the chemicals that are used to produce chlorine dioxide. Chlorine dioxide is less expensive than other disinfection methods, such as ozone."

http://www.lenntech.com/water-disinfection/disinfectants-chlorine-dioxide.htm

Unless you are talking about a large commercial pool application with staff available to do the disinfection, you are probably wasting your time considering other alternatives to chlorine.

 

[aliciam]

I am not familiar with the specifics of the chemistry involved, but here is my two cents.

Everyone around where I live is converting their pool systems to a saltwater system. It is supposedly cheaper and easier to maintain.

 

[GarySCWSVI]

Keep the chlorine you are now using. You have received good adice so far, except for the suggestion to convert to a saltwater system. That would still require routine disinfection.

Gary Schreiber, CWS VI
The Purolite Co.

 

[orenda1168]

Chlorine is by far the choice for sanitizing swimming pools and spas. This can be added to the water in a variety of ways, though the current trend is via salt water chlorine generation (SWG), which in my opinion is more user friendly than either tablets (dichlor, trichlor or cal hypo) or sodium hypochlorite (liquid). Although SWG systems are a bit pricy, their ease of use,virtual "set and forget" operation and generally low maintenance makes them a worthwhile choice.

Ozone, as pointed out by Coloeng, requires a residual o0f free chlorine )hypochlorus acid for suitable sanitation, besides the fact that these systems are relatively expensive.

Chlorine dioxide is infrequently used except in some very large commercial installations.

Dfipiso stated a concern with chloramines. Formed as reaction products with hypochlorus acid (free chlorine) and nitrogeneous wastes in water, these can be easily controlled to negligible levels through routine use of liquid enzyme products on the market that greatly accelerate the decomposition and subsequent oxidation of organic residues, thereby providing minimal if any material for reaction with chlorine.

Orenda

 

[dalcazar]

how about using a hydrogen peroxide system?

 

[dfopiso]

your inputs are all helpful
i should give you all stars, can i do that?
i will forward your comments to our chem engr.,
i can only "absorb" so much as i am an elec engr by profession -- i head R&D thats why

 

[orenda1168]

Somewhat like ozone, hydrogen peroxide has a relatively short life span in water with any measurable residue, and therefore requires the use of a persistant sanitizer residual such as provided by chlorine. Beyond this, hydrogen peroxide is not accepted by the USEPA as a recreational water sanitizer.....EPA accepted sanitizers are only chlorine, bromine and biguanide (Baquacil and similar, which for a multitude of other reasons you don't want to consider the use of).

Orenda