Study On Capacity Of Plasma Source At Atmospheric Pressure And Its Degradation Of Odor Compounds In Water

Due to the effects of eutrophication,significant increases in the occurrences of taste and odor(T&O)problem have been observed in such places as eutrophic lakes,reservoirs and other surface drinking water sources,including main T&O substances 2-methylisoborneol and geosmin.What to do with the T&O substances is a global problem facing by the drinking water treatment industry.In this study,the electrical characteristics of the plasma source generator under atmospheric pressure and the concentration of active oxygen species generated were studied and hydroxyl radicals(·OH)generated with strong ionization discharge(SID)and hydraulic cavitation jet was used for quickly and effectively oxidative degradation of the T&O substances in drinking water.The specific experiment project and conclusions are as follows:(1)Taking plasma source as a model,the experiment explored the electrical characteristic of it through current-voltage waveforms and Lissajous grams.The main experiment variable included gas type,gas flow and excitation voltage.It was found that excitation voltage was the key factor affecting its discharge characteristic.(2)The influence of gas environment and gas flow on the ion intensity generated by plasma source was investigated.It was found that ion intensity at air atmosphere was the largest and increases with the increase of gas flow.Taking oxygen as an example,the experiment explored the concentration of the main product ozone generated during the gas discharge process under different influencing factors.It was found that gas flow,excitation voltage,water temperature and pressure outside were the main factors changing ozone concentration.Under the optimal conditions,the concentration of ozone could reach 260 g/m3.(3)Active oxygen species(AOS)such as O2+,O(1D),O(3p),O2-,O3,and so on which ionized and dissociated by high-energy electrons generated in the process of SID,after gas-liquid mixing through venturi,could generate·OH and other active oxygen substances under the effect of hydraulic cavitation.These active substances were collectively referred to as total reactive oxidant(TRO).In this experiment,4-hydroxybenzoic acid was used as a·OH capture reagent which could capture·OH and make qualitative analysis.The two taste and odor compounds 2-MIB and GSM in water could be effectively degraded by·OH generating during strong ionization discharge at air pressure,using headspace solid phase micro-extraction(HP-SPME)combined with gas hromatography-mass spectrometry(GC-MS)method.It was found that the degradation efficiency of 2-MIB and GSM increased with the increase of TRO dosage.The degradation efficiency of 2-MIB and GSM reached 99.2%and 98.8%respectively when the dosage of TRO were 3.49 mg/L and 3.28 mg/L.The content of 2-MIB and GSM after degradation in drinking water had both reached the sanitary standard for domestic drinking water.The degradation effects of different oxidants·OH,KMnO4,H2O2 and ClO2 on 2-MIB and GSM were compared.The experiment showed that conventional oxidants had little oxidative degradation effect on 2-MIB and GSM in water after 30 min of reaction.