Adsorbable organic halogens in contaminated water environment: A review of sources and removal technologies

“Adsorbable organic halogens (AOX)” is a comprehensive index defined as the sum of all halogenated organic compounds which can be adsorbed onto the activated carbon and detected by microcoulometry. AOX have received increasing attention because of their widespread distribution, potential toxicity and bioaccumulation. It is urgent to control AOX pollution due to their hazard to eco-environment and human health. However, a significant gap still exists in our knowledge of the source, pollution extent and character of AOX. This review describes the contamination status of AOX and identifies their key sources, pollution-intensive sectors as well as emission hotspots. Considering the generation of AOX during high salinity wastewater treatments and the accumulation of AOX in sludges, the wastewater treatment plants (WWTPs), which have been neglected previously, are identified as potential sources of AOX. Besides, the performance and innovative improvements of AOX removal technologies are critically evaluated. Different scenarios are proposed to enhance removal efficiency and avoid byproduct generation during AOX treatment processes.