Degradation of Organic Pollutants from Wastewater using Hydrodynamic Cavitation: A review

Hydrodynamic cavitation is a promising technology for the removal of harmful and toxic chemicals from wastewater. In the present work, a critical analysis of hydrodynamic cavitation reactors including the design aspects and approaches to intensify the operation has been presented. Effect of all the influencing parameters on the extent of degradation has been thoroughly discussed along with guidelines for selecting the best operating conditions. Among the commonly applied low pressure non-rotary devices, it has been elucidated that Venturi type configuration gives 10-30% higher extent of degradation than an orifice. The intensification using hydrodynamic cavitation is shown to be strongly dependent on the treatment parameters, catalysts and additives used in the process. Overall, a lower initial concentration, acidic medium and optimum temperature were more significant for degradation of any pollutant including the structure of the pollutant. Intensifying agents like hydrogen peroxide, as well as catalysts like TiO2, sodium persulfate, and ferrous ion activated persulfate, can be used at optimum loading depending on the type of wastewater to enhance the extent of degradation. A hybrid technology, such as hydrodynamic cavitation combined with other advanced oxidation processes like ozone, photocatalysis, and Fenton, has been shown to provide significant process intensification, often synergism. The economic feasibility of the hybrid approach was discussed in order to evaluate the possible use in large-scale wastewater treatment and it has been conclusively established that hydrodynamic cavitation offers promise for industrial effluent treatment.