Processes for the removal of recalcitrant organics from industrial wastewaters

Processes that are suitable for the elimination of recalcitrant organics from industrial wastewaters are reviewed. Most advantageous are separation processes which enable not only reuse of the water phase but also the recycling of the wastewater constituents. Besides separation processes many degradative wastewater techniques are available. However, for the removal of recalcitrant organics biological processes (which are economically beneficial) cannot be chosen, but a variety of nonbiological degradative processes exist which can be divided into oxidative and reductive technologies. The latter are in the research and development state. The chemical oxidative treatment technologies comprise wastewater incineration and wet air oxidation for wastewaters with high organic concentrations, the so-called advanced oxidation processes (AOPs) as e.g. ozone/hydrogen peroxide which generate the nonselective but very powerful oxidant OH radical, and processes with other oxidants as e.g. Fe(VI) compounds or peroxodisulfate. Also electrochemical oxidation of organic wastewater constituents is possible. All degradative processes that do not lead to total mineralization of organic wastewater constituents may form transformation products which sometimes are more toxic than the original organic compounds.