PolyQuat and Shocking with Chlorine

[chem geek]

As to closing a pool, at least where the water temp drops below freezing.

Provided you use a solid cover that blocks the light, little or no algae should grow even at higher temps during fall. And any algae still alive should be killed over the winter by the low tempertures?

Seems to me that if you put a winter cover a green algae pool, that algae should die over the Winter due to low temp and lack of light and you should find a clear pool with the bottom covered with dead algae come Spring.

That seems logical to me, but does it hold true?
.

You also asked earlier if chlorine will breakdown detergents and the general answer is that chlorine will breakdown every organic compound in your pool eventually. It's just that this can be quite slow for certain organic compounds. Generally, chlorine is extremely fast (probably seconds) at combining with ammonia to form monochloramine. It is a little slower (probably a few minutes) to combine with nitrogenous organics to form chlorinated organics. It is then slower (probably minutes to hours) at breaking down monochloramine into nitrogen gas and may take even longer to break down the chlorinated organics, though sunlight might help this process. Pure organics not containing nitrogen would probably take the longest to breakdown.

The PolyQuat isn't just a detergent. What mostly characterizes a detergent (and most clarifiers, for that matter) is a molecule that has a polar (charged) end and another that has a non-polar (uncharged or neutral) end. The non-polar side tends to embed in non-polar organics while the polar side has affinity for water. So the net effect is to cover or engulf non-polar organics presumably letting them filter out better -- that is, PolyQuat is really a clarifer and in fact was used as such before it became known that it was a good algaecide.

You are correct that if you cover your pool to keep out sunlight and the pool water stays cold, then algae should not grow (I think the algae just becomes dormant in cold temperatures -- it probably doesn't get killed unless the water freezes which would burst the cells). However, I do seem to recall some photos on this forum where people have opened up their pool to a green mess and then shocked to get rid of it and I seem to recall such pools being covered. Perhaps the weather warmed up enough that the algae primarily grew just before the cover was taken off, and perhaps the cover wasn't opaque (I don't remember). At any rate, it doesn't take long for green algae to "bloom" and fill a pool.

Richard

[chem geek]

I just wrote an E-mail to Buckman Laboratories regarding this issue of chlorine breaking down PolyQuat so we'll see if they respond. I'll keep y'all posted. We'll get to the bottom of this eventually.

Richard

[fcfrey]

I just wrote an E-mail to Buckman Laboratories regarding this issue of chlorine breaking down PolyQuat so we'll see if they respond. I'll keep y'all posted. We'll get to the bottom of this eventually.

Richard

I guess you haven't heard anything yet from Buckman Labs. From all you've written it sure sound like Quat may be a waste if you follow the BBB method.

[chem geek]

I guess you haven't heard anything yet from Buckman Labs. From all you've written it sure sound like Quat may be a waste if you follow the BBB method.

I haven't heard from them yet and just sent a reminder E-mail. I doubt that PolyQuat is a waste at normal chlorine levels. The chlorine may only combine with PolyQuat relatively slowly at normal levels -- perhaps over a weeks time (given that it takes around 1-2 days at high chlorine levels) and the PolyQuat may be quite effective at preventing algae during that time. Also, I don't know yet if the chlorine combining with PolyQuat reduces its effectiveness (i.e. does it form a combination substance that is still useful or does it breakdown PolyQuat rendering it useless). So we'll still need to wait and see what Buckman says.

Richard

[chem geek]

I received the following response from Buckman Laboratories:

Mr. Falk:
 
Sorry about the delay in getting back to you.  I've been checking into some
literature references and trying to contact some of our water treatment
specialists to find some answers to your questions.
 
1)    The Polyquat 60 product that you mentioned is typically used along with
chlorine at normal use concentrations (low ppm levels of both substances) in
swimming pools.  Chlorine provides a faster kill of bacteria, while the
Polyquat 60 provides better control of algae as well as better water clarity.
The different advantages of these two pool treatments complement each other.
 
2)    While chlorine and Polyquat 60 have been shown to have very little
interaction at low concentrations, there can be some reaction or degradation
at higher concentrations.  For example, Polyquat 60 and bleach should not
be mixed neat, as an undesirable reaction would be expected to occur.
 
3)    In an alkaline solution containing an oxidizing agent, the polymer that
comprises the active ingredient in Polyquat 60 can be cleaved at the sites of
the quaternary ammonium groups, forming shorter polymer chains.  These
shorter chains are still cationic; and, according to some internal lab data
here at Buckman Laboratories, these shorter chains retain their biocidal
activity.  As the chains become shorter, the Polyquat test kit will not longer
respond to and detect them; however, the lack of a response by the test kit
does not necessarily indicate that the biocidal activity has been lost.
 
4)    In our recommended approach for winterization, the pool should be
"shocked" with about 5-10 ppm chlorine to destroy any lingering oxidant
demand, to remove any residual ammonia or chloramine, etc.  After a
couple of days, adjust the pH back to 7.2-7.6 and add Polyquat 60 at the
maximum rate allowed by the label.  This approach allows you to have the
maximum benefit from both chemicals.
 
If you have any other questions, please do not hesitate to contact us.
 
Tom McNeel
Principal Scientist
Buckman Laboratories International, Inc.

So there does appear to be consumption of chlorine by the PolyQuat (shock chlorine has high FC levels and increases the pH of the pool) and this is probably cleavage at the Nitrogen site, but the remaining chains are still effective as an algaecide. However, the recommendation is to first shock with chlorine (mostly to get rid of most organics and/or ammonia in the pool) and then wait for the FC to return to normal levels and make sure the pH is in the normal range. Then, add the PolyQuat in the recommended amount for closing the pool.

In addition to the E-mail, I talked with Dr. McNeel and asked about the method of action of PolyQuat on algae and he said that the cationic nature of the molecule (that means it has positive net charge) binds to and interferes with the negatively charged cell exteriors of most algae and bacteria and prevents the normal transport of food into the cell and waste out of the cell. This process is somewhat slow so it's fine for inhibiting algae, but not quite fast enough to quickly kill bacteria so chlorine is still required for disinfection. This method of action is for the hydrophillic (i.e. "water loving") PolyQuat molecules. There are other quarternary ammonium compounds that are hydrophobic (i.e. "water hating") that operate with a different method of action, but we didn't get into details on that.

He also said that while PolyQuat inhibits and kills algae, it does not harm people, either through skin exposure nor consumption (i.e. drinking pool water that has some PolyQuat in it). [EDIT] Dr. McNeel sent a follow-up E-mail saying that after adding PolyQuat, the circulation pump should be kept running for at least 24 hours to thoroughly distribute it through the pool. My guess is that the heavy molecular weight of the PolyQuat (it's a long-chain polymer) makes it slower to diffuse so lots of circulation is needed. [END-EDIT]

Thanks,
Richard