| Brewing wastewater is a kind of organic wastewater with low pH,high color and high concentration,which will lead to eutrophication of water bodies when discharged directly into rivers to streams,thus posing a threat to water ecosystems and human health.Liquid-phase microwave plasma water treatment technology is a hydroxyl radical（·OH）,hydrogen peroxide（H2O2）and ozone（O3）and other active substances in the role of advanced oxidation technology,because of the advantages of high treatment efficiency,fast reaction speed and low energy consumption,so that the technology has good prospects for application and great market potential.Little research has been reported on the application of liquid-phase microwave plasma.Accordingly,a set of liquid-phase microwave plasma device was developed to simulate ethanol as a pollutant,and the effects of various parameters on the degradation rate and mineralization of ethanol were studied to provide technical support and theoretical basis for the experiments of liquid-phase microwave plasma technology to treat brewery wastewater.Through a series of experimental studies and analysis,the following research results were obtained:（1）Based on the characteristics of plasma technology,a liquid-phase microwave plasma device was developed,followed by debugging the discharge stability of the device and observing the discharge plasma stability and instability through discharge phenomena.The device can generate plasma in situ in liquid,and the electrons and free radicals that generate plasma have high reactivity,and these active particles can act directly on organic matter in wastewater..（2）The effect of liquid-phase microwave plasma treatment of ethanol wastewater was investigated using ethanol solution as a simulated wastewater.The effects of initial volume fraction,initial pH value and initial conductivity value of the solution on the treatment effect of ethanol wastewater were mainly analyzed.The results showed that the liquid-phase microwave plasma could effectively degrade ethanol.Under the condition that the input power was 800 W,the ethanol content of 10%ethanol wastewater was only 0.27%after 15 min of liquid-phase microwave discharge treatment.In addition,the rate of change of ethanol content slowed down with the increase of initial volume fraction of ethanol,and the degradation rate of treating higher volume fraction ethanol wastewater was slower.Meanwhile,neutral and acidic environments are more favorable for ethanol degradation.When the initial conductivity of ethanol solution varied in the range of 20-2000μs/cm,only 0.34%ethanol content remained after 15 min of treatment with liquid-phase microwave plasma,indicating that the initial conductivity did not affect the degradation effect of liquid-phase microwave plasma on ethanol wastewater.The removal of COD and TOC from ethanol wastewater could reach about 99%regardless of changing the volume fraction,pH or conductivity of the initial ethanol solution.In contrast,the electrochemical oxidation method treated ethanol wastewater and the COD removal rate reached 39.60%after 10 h of treatment;therefore,liquid-phase microwave plasma could treat ethanol wastewater more effectively,with COD removal rate close to 100%within 10 min.（3）During the treatment of brewing wastewater by liquid-phase microwave plasma technology,the pH of the wastewater decreases continuously and the conductivity of the solution increases continuously;the ethanol content decreases from 2.21%to 1.52%after 10 min of discharge treatment;the removal rate of COD in brewing wastewater can exceed 30.24%,and at the same time,the removal rate of TOC reaches 34.90%. |
