How does pool chlorine/filter do its thing?

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The discussion revolves around the effectiveness of chlorine in clearing cloudy pool water by killing bacteria. The primary question raised is how the remnants of dead bacteria are managed by the pool's sand filter. One hypothesis suggests that dead bacteria dissolve into simpler components that do not cloud the water, thereby making it clearer without the filter's involvement. However, it is noted that the filter's role becomes crucial once bacteria are killed, as it can then handle the dead cells rather than the rapid growth of live bacteria. The conversation also touches on the types of materials used in filters, specifically the differences between sand and diatomaceous earth, and how their shapes and porosity affect filtering efficiency. The importance of filter maintenance is highlighted, with a mention that sand should be replaced after about ten years due to wear. Overall, the thread emphasizes the interplay between pool chemistry and filtration systems in maintaining clear water.
DaveC426913
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< preamble >
Not sure if this belongs in physics, chemistry or engineering.

I feel sort of silly, because I should know this. I'll probably do a face-palm when I get the answer.
< /preamble >

My pool has gotten cloudy so I've thrown some chlorine in. This killed the bacteria allowing the filter to remove it, and my pool is now clear.

I know what the chlorine does; it causes the bacteria's cells to rupture, killing them.


My question: What is it about exploded bacteria bits that allows the sand filter to sweep them up?

My first hypothesis: The filter is actually not involved. Suspended bacteria are significant in size enough to cause cloudy water. Contrarily, dead bacteria dissolve into their comiponent parts (various gases, ions, salts) which, being much simpler molecules or even atoms, go into solution. As solutions, they are transparent. i.e. the components of the bacteria are still there (though now harmless), but they no longer affect the clarity of the water.
 
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Doesn't the filter charge consist of diatomaceous Earth rather than sand?
 
Phrak said:
Doesn't the filter charge consist of diatomaceous Earth rather than sand?
Some are, some are not. http://www.haywardnet.com/inground/products/filters/Pro_Series_Top_Mount.cfm" .
 
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I thought it was more that if they are alive and multiplying, the filter can't keep up with the growth. If you kill them, then the filter just needs to handle the dead bodies and not all the growth.

Usually it's algae that grows in pools and makes them visibly cloudy. If it were bacteria, that would be quite the toxic area if it was cloudy. :bugeye:
 
DaveC426913 said:
Some are, some are not. http://www.haywardnet.com/inground/products/filters/Pro_Series_Top_Mount.cfm" .

You've got me wondering what sort or shapes the grains should be to best perform filtering. Both high porosity and places for debrit to cling or bond would seem to be important. Which would be best; sharp edged sand, or rounded? I think that diatoms would be very sharp. Or maybe it makes little difference.

A magnifying glass could answer what kind you are using. There should be magnified pictures of sand on the net.

...So I pulled up a few.

http://www.icbm.de/pmbio/mikrobiologischer-garten/pics/for02.jpg


2413921220_20b451a90d.jpg



Sand-lg.jpg



20081026233101_172.jpg


Beautiful in magnification.
 
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Phrak said:
You've got me wondering what sort or shapes the grains should be to best perform filtering. Both high porosity and places for debrit to cling or bond would seem to be important. Which would be best; sharp edged sand, or rounded? I think that diatoms would be very sharp. Or maybe it makes little difference.

I read just yesterday that, after ten years or so, "the edges have been worn off" the sand, so it should be replaced.

I also found out that sand and diatomaceous Earth are not interchangeable in a filter.
 

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