Could outdoor pools eliminate cyanuric acid? The chemists at Dryden Aqua say yes, and their answer is Active Catalytic Oxidation, or ACO, a relatively new chemical for the pool and spa industry.
According to the company’s website, ACO is a chemical product consisting of metal oxides and poly silicates that converts short-wavelength, energyintensive ultraviolet rays from the sun into longer wavelengths. By the conversion of the short-wavelength UV light to longer wavelength light, chlorine is protected from photolysis (decomposition by the sun). The half-life of chlorine increases by over 3 times.
In contrast with the traditional chlorine stabilizer, cyanuric acid, ACO amplifies the performance of chlorine to kill bacteria and provides the pool with cleaner, safer water for both private as well as public pools.
That is because the energy released from converting the sun’s energy is used to split water molecules, producing free radicals (hydroxyl radicals and oxygen radicals). They are even more powerful than ozone and can oxidize pollutants such as urea and chloramines completely back to carbon dioxide (CO2), water (H2O) and nitrogen (N2), resulting in no combined chlorine or toxic disinfection by-products.
Sean McDermott, former vice president of sales for Dryden, said has been used extensively in public and private pools in Europe for over 10 years, where many countries prohibit the use of cyanuric acid. For nearly 20 years, it’s been used in sea mammal aquariums.
He says it hasn’t gotten much attention in this country yet because the U.S. relies heavily on trichlor.
“In reality, trichlor is a horrible way to treat a pool and CYA is far more detrimental than it is helpful. I imagine ACO will catch on quickly in the next 3-5 years,” McDermott said.
We had a lot of questions about ACO so we spoke with Philipp Meyer, Managing Director of Dryden Aqua.
SIN: Do pools using ACO still need to use some CYA?
Meyer: ACO completely eliminates the need for cyanuric acid and organic (stabilized) chlorine products.
SIN: Does it raise or lower the cost of pool care?
Meyer: ACO eliminates the need for Cyanuric Acid (CYA) and the use of organic (stabilized) chlorine. ACO reduces photooxidation (break down) of chlorine by the UV of the sun without reducing the active chlorine that is available for oxidation in the pool water. ACO also amplifies the natural UV disinfection power of the sun to help reduce overall chlorine consumption. In salt water pools, the addition of ACO extends the life of the chlorinator. The incremental cost of ACO is offset by the savings in CYA and chlorine.
SIN: The literature says ACO converts short wavelengths into longer wavelengths. Which wavelengths?
Meyer: ACO helps convert the shortwave UV-C into middle- and longwave UV-B and UV-A(greater 300 nm) which is less destructive to chlorine.
SIN: Is it an EPA registered disinfectant?
Meyer: ACO is not a disinfectant and therefore does not require EPA registration. But because ACO protects chlorine and amplifies the UV of the sun, residential pools can be operated at lower free chlorine levels than before.
SIN: What about toxicity? What kind of toxicity testing has been done?
Meyer: ACO is NSF 50 tested and certified, and it is non-hazardous.
SIN: What can you tell us about its use in aquariums?
Meyer: ACO is used in many seamammal systems around the world.
It was originally developed for this purpose. These animals often live under bad health conditions in chlorinated systems similar to human swimming pools.
ACO reduces the need for chlorine, the formation of harmful DPB’s and helps improve the living conditions of these animals.
We also offer an ACO-Bio version of ACO for fish systems.
SIN: Does it get used up in the reactions it performs, or does it remain in the pool?
Meyer: ACO acts as a catalyst, and it is not consumed in the process. However, because of water loss (splashout, backwash, etc.) we recommend regular dosing during the pool season.
SIN: Is ACO made by multiple manufacturers or is it only available from Dryden?
Meyer: ACO was developed by Dr. Dryden, a marine biologist, to reduce the need for chlorine and the formation of harmful disinfection by-products (DBP’s) such as tri-chloramine or THM’s such as chloroform. ACO is only available from Dryden Aqua.
SIN: Is any kind of special equipment required?
Meyer: ACO is frequently used alone or in combination with the Dryden Aqua Integrated System (DAISY).ACO works with any type of filtration (eg. AFM, glass, quartz sand, DE, cartridge) and disinfection (chlorine/saltwater, peroxide). It can be dosed manually or automatically. If dosed automatically, a dosing pump is required. ACO is best dosed manually once per week or once per month directly into the pool/ skimmer.
SIN: What is the dosage?
Meyer: If ACO is dosed manually, the dosage is 1 liq.qt. per 25,000 gal pool volume per week. We recommend the first dosage be double this amount. ACO takes around 1-2 weeks before the full effects are visible.
SIN: Why does it start working only after a couple of weeks? What's with the lag time?
Meyer: Our new and improved ACO has a much shorter lag time. We recommend the addition of a double dose when starting up the pool. This will reduce the lag time to 1-2 weeks. This is the time it takes for ACO to properly cover all surfaces in contact with water. Then simply dose ACO weekly or monthly as preferred.
SIN: Where (in the world) is it used and why is it relatively unknown in the US?
Meyer: ACO has been widely used in Europe for many years and has recently been introduce to Australia and the US. After successfully launching AFM Activated Filter Media first, ACO was only recently introduced to the US commercial pool market.
SIN: When did it first become available?
Meyer: For the pool market, ACO was successfully launched about 10 years ago in the German speaking markets (Germany, Switzerland, Austria), followed by the rest of Europe. Today, ACO is a standard product in European residential and public pools.
SIN: Where can people buy it?
Meyer: ACO is sold through the DrydenAqua commercial dealer network in the US and Canada. Contact email@example.com for an up-to date list. For the residential market, ACO is offered under the “Dr.Dryden’s Enhance Summer” brand, available through most major distributors.
SIN: Where is Dryden's headquarters (in the US, if it has a location here) Meyer: Dryden Aqua has two state of the art manufacturing plants for AFM Activated Filter Media in Scotland and Switzerland. All our chemical products, including ACO, are manufactured by us in Scotland. Our US sales office is in Dallas, TX.