Advanced Oxidation Process

A Advanced Oxidation Process (AOP)The process of water purification is based on the generation of highly reactive radicals, mainly hydroxyl radicals (-OH). These radicals have a very high oxidation potential and can efficiently break down or completely mineralise complex organic and inorganic pollutants, i.e. convert them into harmless end products such as water and carbon dioxide.

How do AOPs work?

Hydroxyl radicals are generated by various methods, including

UV light in combination with hydrogen peroxide (H₂O₂)UV light breaks down hydrogen peroxide into radicals that attack organic compounds.
Ozone (O₃) and hydrogen peroxideOzone reacts with hydrogen peroxide to form hydroxyl radicals.
UV light and ozoneUV light activates ozone to form radicals.
Fenton reactionCombination of hydrogen peroxide and iron(II) ions (Fe²⁺) to generate radicals.
UV/H₂O₂/O₃ combinations and other chemical combinations, depending on the specific application requirements.

These reactions produce short-lived but very effective hydroxyl radicals that are capable of attacking even organic pollutants that are difficult to degrade and cannot be removed by other processes, or only to an insufficient extent.

Applications of AOPs

AOP technology has become increasingly important in various areas of water and wastewater treatment.
Here are the most important applications:

Degradation of organic pollutants

AOPs are particularly effective at breaking down persistent organic compounds such as pesticides, pharmaceuticals, hormones and other micropollutants. These substances pose a challenge for conventional cleaning processes as they are difficult to biodegrade.

Removal of odours and taste

AOPs are used to eliminate undesirable odours and flavours in drinking water. The complete degradation of organic substances means that often associated odour and taste components also disappear.

Oxidation of heavy metals and toxic compounds

Certain heavy metals and toxic substances can be oxidised by AOPs and either removed directly or modified in such a way that they can be filtered out of the water more easily.

Drinking water treatment

In drinking water treatment, AOPs are used to break down contaminants that are difficult to remove using conventional disinfection methods (e.g. chlorination). In combination with filtration systems, they are an effective solution for removing impurities from drinking water.

Removal of pollutants in industrial wastewater

Many industries, including the chemical, pharmaceutical and textile industries, produce wastewater that contains complex organic compounds. AOPs are used to destroy toxic and poorly degradable compounds and to treat wastewater in an environmentally friendly way.

Groundwater remediation

AOPs are also suitable for the treatment of contaminated groundwater, in particular for the removal of volatile organic compounds, solvents and other contaminants that can enter the groundwater through industrial waste or agricultural residues.

Treatment of swimming pool water

By oxidising organic substances and reducing chloramines, the water quality in swimming pools is improved, which helps to reduce eye and skin irritation.

Advantages:

High efficiency in the decomposition of a wide range of pollutants
No formation of toxic by-products, as the end products are mostly CO₂ and water
Flexible use in various application areas

The challenges:

High operating costs, as UV light and chemical additives are often required
Requires careful control and monitoring to ensure uniform radical formation
In some cases, disruptive side reactions can occur that reduce efficiency.