Abstract
In the first part of this two article series on the imperative technologies for wastewater treatment, a review of oxidation processes operating at ambient conditions was presented. It has been observed that none of the methods can be used individually in wastewater treatment applications with good economics and high degree of energy efficiency. Moreover, the knowledge required for the large-scale design and application is perhaps lacking. In the present work, an overview of hybrid methods (the majority are a combination of advanced oxidation processes) has been presented. Hybrid methods viz Ultrasound/H2O2 or ozone, UV/H2O2 or ozone, Ozone/H2O2, Sono-photochemical oxidation, Photo–Fenton processes, catalytic advanced oxidation processes, use of advanced oxidation processes in conjunction with biological oxidation, SONIWO (sonochemical degradation followed by wet air oxidation), and CAV-OX have been discussed with specific reference to the principles behind the expected synergism, different reactor configurations used and optimum considerations for the operating and geometric parameters. An overview of different chemicals degraded has been presented. Some of the important works evaluating the application of these processes to real effluents have been described in detail. Some guidelines for the future work required to facilitate efficient large-scale operation have been given. A model effluent treatment scheme based on the various techniques discussed in the present work has been presented.
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