Advances in chemical water and wastewater treatment
have led to the development of methods termed
advanced oxidation processes (AOPs) or technologies
(AOTs). AOPs can be broadly defined as aqueous
phase oxidation methods based on the intermediacy
of highly reactive species such as (primarily but
not exclusively) hydroxyl radicals in the mechanisms
leading to the destruction of the target pollutant.
Over the past 30 years, R&D concerning AOPs
has been immense particularly for two reasons,
namely (i) the diversity of technologies involved
and (ii) the areas of potential application. Key
AOPs include heterogeneous and homogeneous
photocatalysis based on near ultraviolet (UV) or solar
visible irradiation, electrolysis, ozonation, Fenton’s
reagent, ultrasound (US) and wet air oxidation
(WAO), while less conventional (and consequently
less studied) but evolving processes include ionising
radiation, microwaves, pulsed plasma and the ferrate
reagent. Although water and wastewater treatment is
by far the most common area for R&D, AOPs have
also found applications as diverse as groundwater
treatment, soil remediation, municipal wastewater
sludge conditioning, ultrapure water production,