I first E-mailed to Dick Kersey of Orenda Technologies back in December, 2007 on the chlorine/CYA relationship and how chlorine at appropriate levels can prevent algae growth in spite of high phosphate levels. Not much came from that brief discussion.
I then ran into the Orenda Technologies website in May, 2010 and watched the video on that site and E-mailed again asking to forward to Dick Kersey. Some of the things in the video such as phosphate bonding with hydrogen ion to produce more hypochlorite ion simply isn't true and confuses the facts about what phosphate removers really do which is to remove one form of algae nutrients (inorganic phosphate) that can slow down algae growth depending on how many organic phosphates there are since those are not removed. The video also talks about metals that are prevented from being oxidized, but the metal remover doesn't do that but rather just sequesters any metal ions that are already oxidized.
I received an E-mail back from Harold Evans saying that Orenda was sold from Dick to him and an E-mail conversation began from there. We then talked on the phone and Harold is a really nice guy so he offered to come over and give me some products free to try out in my pool. I already told him that my chlorine demand was low and the pool well maintained so this was an experiment to see if the product would have any effect. He came over and added CV-700 which is mostly enzymes though also has a small amount of phosphate remover in it. He said that normally he sees a lot of bubbles and surface film from the enzymes indicating that they are working (presumably to oxidize organic matter), but when he added the product to my pool there was very little of this reaction. He asked me to continue to use the product weekly which I did. The water started to get dull looking over time, most likely due to the phosphate remover since my pool was high in phosphates (3000+ ppb).
After some weeks, I reported back to Harold that there was no measurable reduction in chlorine demand (to within 0.2 ppm). My 16,000 gallon pool (shown here and here before the treatment) has a mostly opaque electric safety cover though the pool is used every day by my wife for 1-2 hours and longer on weekends when I also use the pool. The daily chlorine demand is around 1 ppm FC. Years ago when there wasn't very much use of the pool, the chlorine demand was around 0.7 ppm so I attribute 0.3 ppm to loss from sunlight and from bather load. The pool is kept warm (85-90║F) so most of the chlorine loss is from chlorine oxidation of the cover, from oxidation of CYA, and oxidation of other organics, metal, etc. This chlorine demand is very temperature dependent as it seems to get cut in half at lower temps somewhat below 80║F and drops a lot at 70║F and below.
Harold then said to try the PR-10000 phosphate remover so I did and it immediately severely clouded the pool (which is not a surprise). Because my wife is swimming every day and needed to use the pool the next day, I used an old polymeric clarifier I had (GLB« Clear Blue«), ran the pump all night, and it was crystal clear by the morning though there were some piles of precipitated lanthanum phosphate I had to carefully sweep into the floor drains (I have no vacuum to waste capability with my cartridge filter and plumbing setup). I knew that the phosphate level was more than 3000 ppb before the treatment and afterwards it was 250 ppb so I later used more and got it down to 125 ppb. Since that time there is still no measurable drop in chlorine demand nor any difference in water quality (other than it becoming clear again after using the clarifier since the earlier enzyme product that has some phosphate remover had made the pool water dull).
So how can one explain the many pools that Harold has seen where his products work to significantly cut down chlorine demand and improve water quality? In commercial/public pools with high bather load, supplemental oxidation can be very helpful and indeed can be essential. Enzymes are one option as are UV, ozone and non-chlorine shock (MPS). Chlorine demand is reduced because chlorine does not need to oxidize as much bather waste. In residential pools, this isn't usually needed, but chlorine demand can be high due to nascent algae growth that occurs when the FC level isn't high enough relative to the CYA level, usually due to continued use of stabilized chlorine. In such pools, a phosphate remover can reduce chlorine demand by slowing down algae growth, up to a point, but of course a properly maintained pool with sufficient FC relative to CYA can do the same thing. Also, some pools can have a lot of organic demand where enzymes might be helpful or are smaller pools with lots of people using the pool. For most residential pools, however, most chlorine demand is from loss from sunlight and neither enzymes nor phosphate removers help prevent that at all.
The PR-10000 can be purchased for $40 per quart or $136 per gallon where one quart will remove 8000 ppb phosphates in 10,000 gallons. Compare this to 3 liters of PhosFree for $23 (7-13% lanthanum chloride) or commercial strength for $40 (15-40% lanthanum chloride) where the latter removes 3000 ppb from 20,000 gallons so 6000 ppb from 10,000 gallons. In 10,000 gallons, the PR-10000 by the quart is $5.00 per 1000 ppb phosphate, by the gallon it's $4.22, while the PhosFree Commercial Strength is $6.67 per 1000 ppb phosphate. Also compare this to SeaKlear phosphate remover here at $29 per quart so for 10,000 gallons that's $3.22 per 1000 ppb so apparently less expensive than the Orenda PR-10000 product.
Note that the Orenda and SeaKlear products require use of a clarifier to clear the water while PhosFree contains a clarifier in the product.