Experimental Study On Degradation Of Refractory Wastewater By Hydrodynamic Cavitation Due To Venturi Tube And Square Orifices Plates

Hydrodynamic cavitation is a new water treatment technology. It is both high efficiency and energy saving. What’s more, it’s easy to be operated and it can handle a variety of refractory wastewater.In this paper, the treatment effect and the effect of different experimental conditions on the degradation of the refractory wastewater were studied by the combination of Venturi tube and square orifices plate hydrodynamic cavitation device which was independently designed in the Hydraulics Laboratory of Zhejiang University of Technology. Firstly, different throat lengths of Venturi tube were used to process the wastewater of nitrobenzene to find out the best throat length. The Venturi tube which has the best throat length was combined with the square orifices plate to be the core of the hydrodynamic cavitation device. Secondly, using the hydrodynamic cavitation device to process the mixture wastewater of p-nitrophenol and nitrobenzene and the effect of the number of the orifices, the size of the orifices, the initial concentration of the mixture wastewater, the cycle time of the wastewater and the cavitation number on the degradation rate was discussed after it. On this basis, the instrument of YE6263was used to monitor the pressure of the downstream of the orifices plate in different operating conditions, and meanwhile the influence of the number of the orifices, the size of the orifices and the shape of the orifices on the pressure was analysed. Following, using the methylene blue as the capture agent of the hydroxyl radical to seek for the conditions which can improve the cavitation intensity by using a double beam-UV spectrophotometer to quantitatively analyse the hydroxyl radicals generated by the hydrodynamic cavitation effect. Finally, the actual dyeing wastewater was used to further validate the conclusions obtained previously. The effect of the velocity, the number, size, shape of the orifices, the initial concentration, the cycle time, the pH of the mixture wastewater, and the cavitation number on the COD and chroma degradation rate was discussed. And the best orifices plate to process the actual dyeing wastewater was found by analyzing.