4 typical questions about AOX

What does the abbreviation AOX stand for?

The abbreviation AOX stands for ‘Adsorbable Organic Halides’. This value gives the concentration of organic halogens, which are components containing chlorine, bromine or iodine, in a water sample. Increased levels are often related to pollution.
 

What are typical sources of AOX?

Halogenated components are widely used both in industry and households for which typical applications are cleaning, disinfecting and degreasing. In addition, the chemical or pharmaceutical industry makes use of large amounts of halogenated solvents, often chlorinated ones such as DCM or TCE, which can end up in wastewater. More complex molecules such as pesticides can also be detected in water.
 

What is the effect of AOX on the environment?

Many AOX molecules do not naturally degrade in the environment and are classified as persistent organic pollutants (POPs). These persistent compounds can accumulate in water courses and the food chain if they are not removed. Some AOX also pose additional environmental and health risks because of their toxicity. Therefore, many countries have strict AOX regulations in place for discharge of wastewater.
 

How can AOX be removed from water?

As the name already indicates, AOX are adsorbable organics, meaning that they adsorb well on activated carbon. Moreover, it is listed as one of the best available techniques (BAT) for AOX removal. Often AOX is only a fraction of the pollution present in wastewater so an integrated set-up with multiple techniques is required to ensure that all levels are well below the discharge limits. Activated carbon is often used as a final polishing step to remove even the remaining traces of AOX.