How does pool chlorine/filter do its thing?

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Discussion Overview

The discussion revolves around the mechanisms by which chlorine and filters work in swimming pools, particularly focusing on the effects of chlorine on bacteria and the subsequent role of sand or diatomaceous earth filters in maintaining water clarity. The scope includes chemical interactions, filtration processes, and the properties of filter materials.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant hypothesizes that dead bacteria dissolve into simpler components that do not affect water clarity, suggesting the filter may not be involved in clearing the water.
  • Another participant questions whether the filter medium is sand or diatomaceous earth, indicating variability in filter types.
  • A different viewpoint suggests that killing bacteria reduces the load on the filter, allowing it to manage the dead bacteria more effectively.
  • Some participants express curiosity about the optimal shape and porosity of filter grains, debating whether sharp-edged or rounded grains are more effective for filtration.
  • Concerns are raised about the longevity of filter media, with one participant noting that sand may need replacement after years of use due to wear.
  • It is mentioned that sand and diatomaceous earth are not interchangeable in filtration systems.

Areas of Agreement / Disagreement

Participants express differing views on the role of the filter and the nature of the filter medium, indicating that multiple competing perspectives exist without a clear consensus.

Contextual Notes

There are unresolved questions regarding the specific mechanisms of filtration and the properties of different filter materials. The discussion also highlights assumptions about the types of bacteria present in pools and their impact on water clarity.

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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