Algae and Microcystin toxins

[Sminor]

I had never heard of microcystin until this weekend as I was affected by the drinking water ban in the Toledo area. It also created quite a stir at work as we use city water in part of our process. So what I learned was that when algae is killed it can release certain toxins - one of which is microcystin. The city gets its water from Lake Erie and apparently the intake was sitting right in the middle of a huge algae bloom. So they were killing off huge amounts of algae in their treatment plant and the microcystin level went above the acceptable level for drinking (1 ppb). Apparently the acceptable level for skin contact is 20 ppb. This got me thinking about my pool. I have a mesh safety cover and typically open in the spring to fairly large amount of algae growth. I kill if off quickly with a SLAM but never realized killing algae could release toxins. I'm wondering if the chemical gurus on here have ever looked into this? I'm thinking the scale of what is killed in a pool algae bloom would be much lower than what the city experienced but who knows? Additionally I found out that testing for microcystin isn't too easy or cheap; took us awhile to find a lab to test our water from work and it cost $125 per sample... On a good note, it sounds like increased FC levels is what they actually used to solve the problem...

Anyone have any input?

 

[jblizzle]

I look forward to reading chem geeks response

 

[JVTrain]

I would wager that adequate pool chlorination recommended on TFP is sufficient to kill your algae and will also destroy microcystin toxin in short order.

There's lots of data here: http://iaspub.epa.gov/tdb/pages/general/home.do You'll need to search for the contaminant and the treatment mechanism from this link.

From the data there, it looks as though 2-3 ppm of chlorine with fairly low contact times is sufficient to eliminate 90%+ of microcystin toxin. After several minutes nearly all of any microcystin present in the pool, if there was any, would be destroyed. I'll defer to those with more experience on the forum (aka chem geek) for a more educated opinion on this matter.

 

[chem geek]

First of all, the microcystin toxins are from blue-green algae which are technically bacteria not algae (they are cyanobacteria which are bacteria that have chlorophyll so use sunlight to capture energy to make organics for growth). So you don't need to worry about your typical green algae producing these toxins.

Second, as Joel noted and in this fact sheet, "when pH is below 8, chlorine is effective for inactivation of microcystin and cylindrospermopsin" (but not anatoxin-a). This presentation refers to CT values for chlorine inactivation of microcystin (from this paper) where it's around 83 at 25ºC and pH 7.5 (interpolating) to go from 50 µg/L to 1 µg/L. The FC/CYA ratio for an SWG pool has an equivalent active chlorine level to 0.04 ppm FC with no CYA so would take 83/0.04 = 2075 minutes or around 35 hours for that level of inactivation. If you were to go to our recommended shock levels of chlorine, that's roughly equivalent to 0.6 ppm FC with no CYA so would take 83/0.6 = 138 minutes or roughly a couple of hours.

So you shouldn't be concerned about this since 1) it's unlikely to get blue-green algae (it does happen, but it's rare) and 2) shocking the pool with chlorine will reduce the level of most toxins well within the timeframe it takes to clear a pool since such clearing usually takes days, not hours.

 

[ptbrunet]

Thanks for this answer chem geek.

Let's say the situation is the grid is down, it's unknown when it will be coming back up, the pool is a backup water supply, the situation has been long enough that the available stored potable water has been consumed, and it's been decided to use the remaining chlorine to sanitize only water that will be consumed as it's drawn from the pool (say 5 gallons at a time), rather than continuing to chlorinate the pool. Will prefiltering to remove the larger particles (assuming this is what should be done in the case of an algae bloom) followed by chlorination followed by a Big Berkey filter be adequate to deal with algae, algae byproducts (if there is such a concern), CYA, salt, and borates?

I do have a Big Berkey but I'm considering how I might rework my RO unit to filter 5 gallons at a time if the Berkey is not the total solution.

Related questions:
- Would mosquito donuts foul the water in this scenario?
- Should I reduce phosphate levels now "just in case"?
- Should I buy some algae-inhibiting tarps and if so what are some to consider?

 

[chem geek]

The fine filtration should be able to remove algae and in some cases even bacteria (depending on the filter), but they usually do not remove dissolved ions or neutral molecules and that includes CYA, salt, and borates. It is not generally a good idea to drink pool water in large quantities, but of everything in the water it is the borates that would be the most risk when consumed in larger quantities (quarts every day). However, the Berkey filters are exceptional and are classified as water purifiers so it is possible they remove CYA, but I'm not so sure about the borates and salt though they say that "inorganic minerals" are reduced below lab detectable levels.

You should probably call and ask them what they think and describe what's in pool water.

 

[ptbrunet]

Here's the response...

First email:

First off, we always recommend using the cleanest source of water possible when using our Berkey outdoor purifiers. If chlorine is the only chemical being added to your pool, the Black Berkey purification elements will efficiently remove the chlorine. Some compounds on the list (Note: I listed chlorine, salt, borates, and CYA) are mineral based; minerals are not reduced as it dissolves at the molecular level. There are some compounds that our elements have not been tested for and have been researching for labs that to test for various pool chemicals. Our elements will raise the PH and make the water more alkaline.

Second email:

The Black Berkey elements are able to take out contaminants at a virus level while the ceramic takes out contaminants at a bacteria level. Yes the Black Berkey will not filter out minerals except contaminants. An RO system could work if you are trying to strip the water off everything including minerals.

My comments/questions:
- It appears that anything dissolved will not get filtered out. But isn't chlorine dissolved? Maybe the Black Berkey has an agent that attracts the chlorine atoms? And thus would "load up" after a while and need changing?
- Apparently H20 molecule are smaller than the molecules of salt, borates, and CYA and thus pass through the pores on the RO membrane while the others don't due to being too large?

 

[SunnyOptimism]

Here's the response...

First email:

First off, we always recommend using the cleanest source of water possible when using our Berkey outdoor purifiers. If chlorine is the only chemical being added to your pool, the Black Berkey purification elements will efficiently remove the chlorine. Some compounds on the list (Note: I listed chlorine, salt, borates, and CYA) are mineral based; minerals are not reduced as it dissolves at the molecular level. There are some compounds that our elements have not been tested for and have been researching for labs that to test for various pool chemicals. Our elements will raise the PH and make the water more alkaline.

Second email:

The Black Berkey elements are able to take out contaminants at a virus level while the ceramic takes out contaminants at a bacteria level. Yes the Black Berkey will not filter out minerals except contaminants. An RO system could work if you are trying to strip the water off everything including minerals.

My comments/questions:
- It appears that anything dissolved will not get filtered out. But isn't chlorine dissolved? Maybe the Black Berkey has an agent that attracts the chlorine atoms? And thus would "load up" after a while and need changing?
- Apparently H20 molecule are smaller than the molecules of salt, borates, and CYA and thus pass through the pores on the RO membrane while the others don't due to being too large?

Thoughts/responses:

- It appears that anything dissolved will not get filtered out. But isn't chlorine dissolved? Maybe the Black Berkey has an agent that attracts the chlorine atoms? And thus would "load up" after a while and need changing?

Chlorine is typically removed from water through an irreversible chemical reaction that binds the Cl atom. For instance, sodium thiosulfate will remove free chlorine from solution by converting it into sodium chloride. Also, some colloidal metals (like platinum and silver) will react with chlorine forming insoluble metal chlorides. So yes, after a certain amount of use, your Berkey filters capacity to remove chlorine will go to zero.


- Apparently H20 molecule are smaller than the molecules of salt, borates, and CYA and thus pass through the pores on the RO membrane while the others don't due to being too large?

It's not about size but about about charge. The polymer membrane used in an RO filter (typically polyamide) allows water molecules to pass through it's porous structure but is able to reject ionized species like Na+, K+, borates, etc. CYA is rejected as well. Chlorine typically has to be removed from the water first or else the chlorine will attack and degrade the polyamide RO membrane and supporting polymer substrates.

In order for RO filters to work for desalination purposes, several RO filters need to be cascaded together so that each stage produces successively less saline water before passing it on to the next stage. As well, high pressure pumps (typically operating in excess of 250PSI) need to be employed or else the reject fraction of waste water will be too high as to make it inefficient.

 

[ptbrunet]

In this case my salt level is 1200 ppm. Would one unit be enough?

My house pressure is probably something like 40/50 psi. The Culligan tech said I loose about 50% (which I assume I could capture and reprocess).

In a grid down situation the city towers will eventually empty and I'll loose pressure. I've seen some discussions where people either use 12v pumps or gravity feed of on the order of 10'. But I've only started to investigate how I'd use my current installed RO unit or a portable "just in case" unit with either a 12v pump or gravity feed. I am in a two story house so shouldn't have any problem getting 10' or more of gravity feed.

And chlorine shouldn't be a problem because I would have stopped chlorinating the water long before the situation.

 

[SunnyOptimism]

A household style RO filter would be incapable of efficiently generating drinking water from pool water. The membranes in household RO systems are designed for low pressures and have high rejection fractions. Also, you can not capture the rejected waste water and reprocess it as it's salinity would be greater than the salinity of the starting water.

In the case of some post-apocalyptic, end of world scenario, you should worry more about the mindless hordes of zombies roaming around looking to eat your brain than about setting up a backyard RO filtration plant.....

If you seriously want to turn pool water into drinking water without the aid of the electric grid, then solar/thermal distillation would be the most efficient and easy to implement method of desalinating pool water. RO is too complicated to pull off without the aid of electric power and high pressure pumps.


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[ptbrunet]

Thanks SO,

>The membranes in household RO systems are designed for low pressures
I assume you mean I need a low pressure source. I had planned on either gravity feed from about 12 feet up or a battery powered 12v pump. I think the spec I saw yesterday was .4 psi per foot of elevation. That's ~5 psi. I have seen some folks documenting that their small RO systems can generate water at less than that. (It would be a slow generation process but enough drinking water to live on.) I'd use solar/battery/pump though.

>and have high rejection fractions.
I wouldn't mind loosing 50 to 75% since I have a starting point of 15K gallons.

>you should worry more about the mindless hordes of zombies
One of the seemingly never ending things to plan for. It's happened in other parts of the world unfortunately too many times and survivors have documented how they coped with it.

>solar/thermal distillation would be the most efficient and easy to implement method of desalinating pool water.
Do you have suggested reading?

 

[chem geek]

My comments/questions:
- It appears that anything dissolved will not get filtered out. But isn't chlorine dissolved? Maybe the Black Berkey has an agent that attracts the chlorine atoms? And thus would "load up" after a while and need changing?

Yes, chlorine is dissolved but it is likely removed in a Berkey filter because they may have granulated activated carbon or adsorbing materials. Note that they reduce some organic molecules such as trihalomethanes and volatile organic compounds. They remove heavy metals mostly from ion exchange so they remove quite a lot of dissolved ions and molecules. I would guess that their filter might reduce CYA, but probably not borates (boric acid).

 

[ptbrunet]

Too bad I added borates and too bad I refreshed the borax this Spring. I guess in the emergency situation I am thinking of an RO filter would eliminate the boric acid. But I am learning tonight that using an RO is not a good idea for every day use due to the water being demineralized and thus extracting calcium from bones and iron from blood (and who knows what else) in a rebalancing process and causing long term degenerative disease.

 

[chem geek]

For emergency purposes, drinking water without minerals is not going to harm you. That is a long-term problem and presumably any emergency isn't going to last for months or years, but more likely days or perhaps a few weeks. Also, presumably you will be eating which will provide other sources of calcium and iron to replenish what may be diluted through drinking RO'd water.

Your hot water heater is a good source for drinking water if you turn off the intake valve right after an emergency to prevent any contamination from entering the tank.

 

[Swampwoman]

^just to add to the notion, though I realize its whimsy, I'm not convinced that at a rate of 50 ppm of borates would be particularly adverse to human health anyway...some folks in the alternative health world actually take it therapeutically for arthritis and yeast infections -- about an 1/8th tsp in a litre of water in the case of the former and as a suppository in the case of the latter - and the latter is a commercial treatment

In the old days, folks with arthritis would "take a pinch."

So toxicity relates to levels...and if a dog can drink 4 gallons of pool water before its toxic, my bet is so can a human in the zombie apocalypse...but that's just a guess

 

[ptbrunet]

Here's a question I had in a related thread but I don't think I ever got an answer to:

Does it make sense to reduce phosphates "just in case" of an extended power down event?

Maybe a better thing to do would be to cover the pool with an opaque tarp after the FC drops to 0? That way there is one less "adjustment" to consider when thinking about the purification process.

My current plan if the situation ever arises (out of water after an extended power down event) is to wait for the FC to drop, cover the pool, run a 5 gallon bucket at a time through a sand filter, then through an RO unit. I haven't yet selected a portable RO unit so am open to any advice on that.

 

[SunnyOptimism]

Here's a question I had in a related thread but I don't think I ever got an answer to:

Does it make sense to reduce phosphates "just in case" of an extended power down event?

Maybe a better thing to do would be to cover the pool with an opaque tarp after the FC drops to 0? That way there is one less "adjustment" to consider when thinking about the purification process.

My current plan if the situation ever arises (out of water after an extended power down event) is to wait for the FC to drop, cover the pool, run a 5 gallon bucket at a time through a sand filter, then through an RO unit. I haven't yet selected a portable RO unit so am open to any advice on that.

Not that I'm a moderator or anything, but you kind of hijacked the OPs thread. You should probably post your question in a separate thread with a descriptive title that way other people who might have similar scenarios and ideas can respond to you.


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[chem geek]

You can still add chlorine if you do some manual brushing and mixing and covering with an opaque cover will minimize chlorine loss, but you could also add Polyquat 60 and again manually mix in that situation. Obviously, you don't add over a return flow but drizzle around the pool and then brush and mix around the pool.

The problem with using a phosphate remover is that you have to use it in advance. Also, unless you have a lot of power outages, dealing with a pool that starts to go south is usually recoverable pretty quickly.

 

[ptbrunet]

Thanks for the reminder SO.