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Advanced Oxidation Processes (AOP) have emerged as a cutting-edge solution in the purification and disinfection of swimming pool water, offering an eco-friendly alternative to traditional chlorine-based systems. This blog post delves into the science behind AOP, elucidating how it functions and its role in ensuring cleaner, safer, and clearer pool water.

The Fundamentals of AOP

At its core, AOP refers to a set of chemical treatment procedures designed to remove organic and inorganic materials from water through the generation of highly reactive species, notably hydroxyl radicals (•OH•OH). These radicals possess an extraordinary oxidation potential, higher than that of chlorine and ozone, making them highly effective at breaking down pollutants, pathogens, and organic matter on a molecular level.

The Science Behind AOP

The effectiveness of AOP in disinfecting swimming pool water lies in its ability to produce hydroxyl radicals. These radicals are formed through the interaction of UV light with ozone (O3), among other precursors. The process typically involves two key stages:

Generation of Precursors: UV lamps or corona discharge methods are commonly used to produce ozone, one of the primary precursors in the AOP system.

Formation of Hydroxyl Radicals: When ozone (or another precursor) is exposed to UV light, hydroxyl radicals are formed.

These hydroxyl radicals are incredibly short-lived but highly reactive, allowing them to attack and break down contaminants at a molecular level. They react with organic compounds, pathogens, and even some inorganic substances, converting them into water, carbon dioxide, and other less harmful substances.

Advantages of AOP in Pool Disinfection

Eco-friendly Disinfection: AOP processes eliminate the need for high concentrations of harmful chemicals, reducing the presence of chemical residuals that can lead to skin irritation, respiratory issues, and other health problems associated with traditional pool disinfection methods.

Broad-Spectrum Efficacy: The high reactivity of hydroxyl radicals allows for the efficient destruction of a wide range of contaminants, including bacteria, viruses, algae, and organic matter, that are resistant to other forms of treatment.

No Chemical By-products: Unlike chlorination, AOP does not produce harmful by-products such as trihalomethanes (THMs) and chloramines, which are associated with negative health impacts.

Implementing AOP in Pool Systems

For AOP systems to be effective in pool disinfection, several factors must be considered, including the intensity of UV light, the concentration of ozone, and the flow rate of water through the system. Advanced systems, like the Purity AOP, optimize these parameters to ensure maximum efficiency across varying conditions.


Advanced Oxidation Processes represent a significant leap forward in pool water treatment technology. By leveraging the power of hydroxyl radicals, AOP systems offer a more effective, environmentally friendly alternative to traditional disinfection methods. As the technology continues to evolve, it holds the promise of setting new standards for water quality in residential and commercial swimming pools alike.


The Advanced Oxidation Process (AOP) is revolutionizing pool disinfection by offering an effective, chemical-free method to purify water. Central to the efficacy of AOP systems is the generation of hydroxyl radicals, highly reactive species capable of degrading organic contaminants and pathogens. After studying the advantages of dry reactors over the prevalent wet reactor approach Purity AOP determined the scientific evidence mandates employing a dry reactor mechanism over traditional wet reactors, particularly in scenarios involving highly contaminated or cloudy pool water.

Understanding Hydroxyl Radicals and AOP

Hydroxyl radicals (⋅OH⋅OH) are among the most powerful oxidizing agents available, capable of reacting with a wide range of organic compounds and pathogens, rendering them harmless. In the context of pool disinfection, AOP systems leverage these radicals to achieve unparalleled water clarity and safety without the drawbacks associated with chemical disinfectants like chlorine.

The generation of hydroxyl radicals in AOP systems typically involves the use of ozone (O3) and ultraviolet (UV) light. Ozone is introduced into the water, where it is then exposed to UV radiation, facilitating the conversion of ozone molecules into hydroxyl radicals. This process can occur in either a wet or dry reactor environment.

The Case for Dry Reactors

The distinction between wet and dry reactors lies in the phase in which the ozone is converted into hydroxyl radicals. In dry reactors, ozone gas is exposed to UV radiation before it encounters the pool water, while in wet reactors, this conversion process happens within the water body. The advantages of using a dry reactor, especially in cases of highly contaminated or cloudy water, are multifaceted:

Efficiency of Hydroxyl Radical Generation: In wet reactors, the presence of impurities and particulate matter in cloudy or heavily contaminated water can consume ozone molecules through side reactions before they are converted to hydroxyl radicals. This reduces the efficiency of the AOP process. Conversely, dry reactors generate hydroxyl radicals outside the water matrix, ensuring that a greater proportion of ozone is efficiently converted.

UV Radiation Penetration: Water, particularly when turbid or cloudy, can significantly attenuate UV radiation, diminishing its ability to catalyze the conversion of ozone to hydroxyl radicals. In dry reactors, the interaction between ozone and UV light occurs in an environment uninhibited by water, allowing for optimal UV penetration and, consequently, more effective radical generation.

Longevity and Cost-effectiveness: Dry reactors avoid the corrosive effects of water and dissolved chemicals on the reactor’s internal components, such as UV lamps and the reactor vessel itself. This not only extends the lifespan of these critical components but also reduces maintenance costs and downtime, contributing to a lower total cost of ownership.

Operational Flexibility: Dry reactors can maintain consistent performance across a range of water qualities and contaminant levels. This adaptability is particularly advantageous for pool systems that may experience significant fluctuations in water clarity or contamination, ensuring effective disinfection under varying conditions.

The use of dry reactors in AOP systems for pool disinfection represents a significant advancement in water treatment technology. By circumventing the limitations associated with wet reactor designs, dry reactors offer enhanced efficiency, cost-effectiveness, and operational flexibility. This is particularly pertinent in scenarios involving highly contaminated or cloudy water, where traditional methods may falter. Through the scientific lens, it is evident that the strategic integration of dry reactors in AOP systems paves the way for superior water quality, aligning with environmental sustainability and public health goals.