Pinellas County, FL Pool Study 1992 (1994)

[chem geek]

(...CONTINUED FROM PREVIOUS POST)

FURTHER EXPERIMENTS AND FIELD STUDIES
So my hypothesis that there are other chemicals that behave like CYA but that are not being measured is intriguing, but how do we go about proving if this is true or not? If we can find a pool that is like #318 or any other pool without CYA but with a reasonable FC, such as 1, and perhaps not in too much sun (so we know that the FC is being maintained), then we can measure the ORP in that pool as well as the specific HOCl concentration (using any of several techniques) and see if they are indeed measuring very low. I suspect that they will since that was the entire basis for the ORP industry and their studies.

If it is confirmed that pools measuring normal to high FC are measuring very low HOCl without any CYA to explain it, then samples of such water should be analyzed for their contents. I’m not sure what technique would be best, but a mass spectrometer might give a clue as to the chemical weights of the mystery chemical and we already know that in a pool such as #318 there will be a reasonable amount of it for measurement (in the hundreds of ppm). Another approach might be to look for nitrogen sites since they seem to be the ones where hydrogen is substituted for chlorine in both CYA and ammonia as well as other chlorinated organics (combined chlorines). Anyway, this now goes well beyond my abilities since I’ve been out of college for over 23 years and haven’t kept up with the latest in chemical analysis (I’m not a chemist; I do mostly software engineering and imaging and color algorithms).

I’d be very interested to know what you think about all of this and if you would be willing to pursue this investigation further.

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In addition to sending the above as an E-mail (with attachments) to a manufacturer/distributor of pool chemicals, I also sent it to a manufacturer of Trichlor/Dichlor products, [EDIT] and I have heard back from the latter and they have been very busy so perhaps that is why I have not heard back from the former [END-EDIT]. Ideally, I would like to put together a presentation that sums up what we've learned here on this forum, not only about chlorine/CYA, but also about lowering TA to reduce rising pH (especially in SWG pools), how to lower TA properly (through low pH and aeration), chemical equivalents among product brands (and store products -- e.g. baking soda, bleach), etc. I then would like that presented at the next Pool & Spa Expo or similar trade show so that pool dealers and distributors can get some better education and resolve customer pool problems more quickly. Many people use a pool service because they simply do not want to bother with brushing their pool or adding chlorine regularly and people still need to buy equipment and occasionally some specialty chemicals so it's not as if the industry will go away with better education. Some people will simply not maintain proper chlorine levels regularly and using an algaecide will help them in that case -- it's not cheap, but that's a choice a consumer can make. The goal is to at least get rid of the false claims or misinformation that seems fairly rampant in this industry and to shift the focus to a higher level of integrity based on truth and real consumer needs. Any suggestions for how these goals can be best accomplished are most welcome.

[EDIT]
This link to the U.S. Patent Office shows a patent that describes how glycoluril binds to chlorine more strongly than CYA does, thereby increasing protection from sunlight to go from a chlorine half-life of 6-7 hours to around 25 hours. It also appears to have lower disinfecting chlorine for the same total chlorine level. It also shows lower rates of disinfection by-product production and outgassing of monochloramine. This is all consistent with the "mystery" chemical that I hypothesized might exist. What I do not yet know is whether chlorine bound to glycoluril will get released fast enough to show up in the Free Chlorine test. If it does, then this is exactly the kind of chemical that could explain the Pinnelas study results, though this is just an existence proof of the concept, not an actual identification that this is the actual chemical in the Pinnelas pools (nor a proof that such a chemical is truly what is going on). Nevertheless, this is very encouraging and may lead to better tests to predict bacteriological safety using standard chemical tests (as opposed to ORP or HOCl sensors).

So far, what this means to residential pool users, is that though the chlorine/CYA relationship is still very likely to be true (the laws of equilibrium chemistry have not changed), there may be other chemicals that act like CYA and get bound to chlorine reducing its effectiveness. We haven't seen data from residential pool users for this since there hasn't been a single reported case of green algae when maintaining chlorine levels vs. CYA levels according to Ben's table (roughly the 0.03 ppm HOCl column in my table for Ben's Min equivalent). At least I could not find any exception -- if anyone can, please let me know. I do know that the few cases of mustard/yellow algae required higher levels of chlorine to keep away, but we sorted that out to be roughly the Max level in Ben's table (roughly the 0.07 ppm HOCl column in my table). Black algae seems to be even more rare in residential pools and brushing plus chlorine seems to get rid of it most of the time.

I also found this patent which combines Trichlor with glycoluril to have it be more slow-dissolving, but it would also add glycoluril to the water that would have the characteristics described above. It does not appear that this combination is in any current products. Also, some of the pools with high FC and high HPC counts in the Pinnelas study had no CYA so direct organic introduction of a CYA-like substance seems more likely. Glycoluril is formed from a combination of urea (obviously present in some pool water, though usually reacts with chlorine to form chloro urea intermediates and to then break down to nitrogen and carbon dioxide gasses) and glyoxal (not clear where that comes from -- *maybe* an oxidized breakdown product from some organics??? more information may be found here). The concentration of urea in urine is about 400 millimole/liter or 24,000 mg/l (ppm) while in sweat the concentration of urea is around 22 millimole/liter or 1300 mg/l (ppm). The concentration of glyoxal in human urine is 132 micromoles/liter or about 7.7 mg/l (ppm). However, the production of glycoluril from glyoxal and urea normally requires heat and a very acidic environment so I doubt the glycoluril is coming from people. Again, I do not know if glycoluril is the mystery chemical explaining the anomalous data or if something else is going on.
[END-EDIT]

(END OF MULTIPLE SEQUENTIAL POSTS)

[chem geek]

Ben, I cannot edit my post (if possible, please give me that ability even for old posts). I need to correct the link to the Pinellas County study since it has been dead for a while. I asked Oxy Chemical to rehost the study on their site since NSPF took it down and they have now down so. So the first "This link" in the first post should go to this link where there are links to the study and its appendices under the "Technical Information" section. Thanks.

[PoolDoc]

It's fixed. -ben