The AOX (Adsorbable Organically Bound Halides) (the X is generally used in chemistry as an abbreviation for any halide) is a group parameter in chemical analysis that is primarily used to assess water and sewage sludge. The sum of the organic halides that can be adsorbed on activated carbon is determined. These include chlorine, bromine and iodine compounds. Organic fluorine compounds are not detected by this analysis method. Since the chlorine-containing compounds usually clearly predominate among the organically bound halogens, mg Cl/l was used as the unit for AOX.

source: https://www.chemie.de/lexikon/Adsorbierbare_organisch_gebundene_Halogene.html