The Study On Treatment Of Landfill Leachate By Hydrodynamic Cavitation Enhanced Potassium Ferrate/Chlorine Dioxide

The landfill leachate produced by sanitary landfill has the characteristics of high organic concentration and high toxicity,which will seriously harm the environment.In this paper,the landfill leachate from a domestic waste landfill site is taken as the research object,and the removal rates of COD and UV254 are taken as the main indexes.On the basis of the previous research of the research group,two new treatment technologies of potassium ferrate（K₂FeO₄）or chlorine dioxide（ClO₂）enhanced by hydrodynamic cavitation（HC）are proposed.The main findings of the study are as follows:（1）Fluent software was used to simulate the cavitation strength of orifice plate cavitator under different inlet and outlet pressure conditions,and the cavitation number was calculated.The results show that:a.When the outlet pressure is 0 MPa,increasing the inlet pressure can improve the cavitation strength,but when the inlet pressure is over 0.4 MPa,the cavitation strength will weaken;b.If the inlet pressure remains the same,the cavitation intensity can be improved by increasing the outlet pressure.However,when the inlet pressure is 0.6 MPa,the outlet pressure is 0.4 and 0.5 MPa,the vapor hold up is too low,and the cavitation intensity will be reduced;c.The inlet and outlet pressure with the strongest cavitation strength is the inlet pressure 0.5 MPa and the outlet pressure 0.3 MPa.（2）Firstly,the effect of treating Rhodamine B（RB）simulated wastewater by HC alone under different inlet and outlet pressure conditions was investigated,and the flow rate of main channel was monitored.Secondly,RB and benzo[a]anthracene（B[a]A）simulated wastewater were treated by HC/ClO₂technology to verify the experimental results.The results showed that:a.When HC was alone,the three groups with inlet pressure of 0.4,0.5 and 0.6 MPa all had the best RB treatment effect when the inlet and outlet pressure difference was 0.4 MPa.The inlet pressure of 0.5 MPa and outlet pressure of 0.1 MPa had strong cavitation intensity and moderate flow rate,and the RB removal rate was the highest;b.When 5 mg/L ClO₂was added,the 60 min RB removal rate difference of the three inlet pressure groups was not significantly improved compared with that of HC alone;c.When 25 mg/L ClO₂is added,the RB removal rate difference between the three will increase significantly.The inlet pressure0.5 MPa and outlet pressure 0.1 MPa still have the best effect,which is 8.52%higher than that when the inlet pressure is 0.4 MPa and the outlet pressure is 0 MPa（only the optimal condition of the inlet pressure is optimized）;d.Adding 25 mg/L ClO₂at inlet pressure 0.5MPa and outlet pressure 0.1 MPa,the removal rate of 90 min B[a]A is 6.4%higher than that at inlet pressure 0.4 MPa and outlet pressure 0.1 MPa,and the enhancement factor is 1.66.（3）Experimental study on the treatment of landfill leachate after coagulation by HC/ClO₂.Under the operating conditions of inlet pressure 0.5 MPa and outlet pressure 0.1MPa,the effects of pH and the dosage of ClO₂on the COD removal efficiency were investigated.The results show that under the optimal conditions of p H=5 and the dosage of ClO₂is 25 mg/L,the COD removal rate of 100 min is 52.94%.（4）Experimental study on the treatment of landfill leachate raw water by HC/K₂FeO₄.Under the operating conditions of inlet pressure 0.5 MPa and outlet pressure 0.1MPa,the effects of p H and K₂FeO₄dosage on the treatment effects of COD,UV254 and BOD₅were investigated.The results show that:a.The optimum pH of HC/K₂FeO₄is 4;b.For COD and BOD₅,the optimal dosage of K₂FeO₄is 1 g/L,and the removal rate of 70 min is 40.69%and 17.39%,respectively;c.The optimal dosage of UV254 and K₂FeO₄was 4.95g/L,and the removal rate was 79.46%after 70 min;d.BOD₅/COD value does not change with the change of dosage,and only fluctuates around 0.6.Compared with raw water,the maximum improvement rate of biodegradability is 61%.