Killing Algae

[setsailsoon]

Folks,

I'm still new to this site and I'm very interested to understand things which is partly why I like this site so much. I've got a couple of very simple questions. How does algae die and what is the process? What happens to the chlorophyll? Does the chlorine react with the strong + charge of the cell wall proteins that keeps the single cells from clumping up when they're alive or is there some other mechanism? The more I read about the killing of algae and filtration the more questions I have. So I thought I'd start at the beginning (or maybe the end from the algae cell's point of view).

Thanks in advance.

Chris

PS If I'm in the wrong area please do move this to the right forum area.

 

[JoyfulNoise]

Algae and other pathogens are primarily killed by the active chlorine compound hypochlorous acid (HOCl). If you look up an image of HOCl (say on Wikipedia), you'll see that it looks A LOT like a water molecule. The cells of living pathogens will take in HOCl much like they take in water and, once inside, the HOCl will cause a lot of intracellular damage to both organelles (mitochondria, ribosomes, etc) and the DNA. It is this damage that causes cellular death.

That's the simple answer....

 

[setsailsoon]

Matt,

Thanks so much that makes a lot of sense. So the HOCl looks to be very polar as it should to be so soluble in water anyway. Then after the contents of the cell are dumped into the pool I would guess the chlorophyll reacts over time to form salts of the metal contained in it as well since it's pretty unstable? And a lot of the nuclear material eventually react to form chloramines? Next step would be the filtration... looks like most of the cartridges are made of a polyester fiber like Reemay 2040. It's only 90% efficient at best with particles 80-100 microns and much lower with particles the size of algae (15 microns or so). I'm guessing the particles and the dead cells but not yet ruptured cells now have no strong charge to cause them to repel each other and they clump together... which would explain how the very small cells get removed in my fairly large pore sized filter?

Chris

 

[kimkats]

CRB I have to say you ask some in depth questions! You must like to learn and then some! I have enjoyed learning with you!

Kim

 

[setsailsoon]

CRB I have to say you ask some in depth questions! You must like to learn and then some! I have enjoyed learning with you!

Kim

Kim,

Thanks for the kind words. I sure don't know enough to help any other people here yet but I'm glad that the answers to my questions are at least interesting to people other than me. And of course most of the credit goes to those that produce the in-depth answers.

Chris

 

[JoyfulNoise]

Sorry, I meant to respond further but life in my house gets hectic at times.

I did do a little searching around the "inter-webs" on your question and the best I could come up with, outside so very esoteric biology research journal articles, is an exceedingly long study done on cyanobacteria (sometimes called "blue-green algae" which is actually a form of bacteria that uses photosynthesis to generate energy). The study was done in the context of drinking water processing where taste and smell come into play. The conclusion was basically that the use of oxidation processes (chlorine and ozone) can lead to the release of intracellular organic matter (IOM), such as chlorophyll and other chemicals, that can undergo further oxidation which can lead to the formation of taste and odor generating compounds. The recommendation is that drinking water producers should use biological filtration methods to reduce the number of live organisms in the water before treating the water with oxidizing chemicals. You can fund the study HERE.

As far as how this might be relevant to pool water, well, the recommendations don't apply much. Chlorine is going to kill and destroy algae and biological organisms. Death may or may not result in the release of IOM. Also, chlorine reacts with lots of chemical compounds but not all (eg, not very reactive toward long-chained fatty acids) and not all organic compounds that react with chlorine necessarily form combine chloramines or volatile organic halogens. More than likely, most of the biological/organic matter is killed and stays resident in the filter media. This is why it is very important to properly clean and maintain your pool filter and follow proper backwashing and annual cleaning practices. Most of this organic and biological detritus will be flushed out of the system with proper filter cleaning.

 

[setsailsoon]

Sorry, I meant to respond further but life in my house gets hectic at times.

I did do a little searching around the "inter-webs" on your question and the best I could come up with, outside so very esoteric biology research journal articles, is an exceedingly long study done on cyanobacteria (sometimes called "blue-green algae" which is actually a form of bacteria that uses photosynthesis to generate energy). The study was done in the context of drinking water processing where taste and smell come into play. The conclusion was basically that the use of oxidation processes (chlorine and ozone) can lead to the release of intracellular organic matter (IOM), such as chlorophyll and other chemicals, that can undergo further oxidation which can lead to the formation of taste and odor generating compounds. The recommendation is that drinking water producers should use biological filtration methods to reduce the number of live organisms in the water before treating the water with oxidizing chemicals. You can fund the study HERE.

As far as how this might be relevant to pool water, well, the recommendations don't apply much. Chlorine is going to kill and destroy algae and biological organisms. Death may or may not result in the release of IOM. Also, chlorine reacts with lots of chemical compounds but not all (eg, not very reactive toward long-chained fatty acids) and not all organic compounds that react with chlorine necessarily form combine chloramines or volatile organic halogens. More than likely, most of the biological/organic matter is killed and stays resident in the filter media. This is why it is very important to properly clean and maintain your pool filter and follow proper backwashing and annual cleaning practices. Most of this organic and biological detritus will be flushed out of the system with proper filter cleaning.

Matt, sorry for the long delay. For some reason I never saw your final response here. Your research makes a lot of sense and helps answer my questions. Thanks so much for taking the time to research this issue for me. Chris

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