Design And Application Study Of Bioaerosol Collector

Bioaerosol is a kind of colloidal system consisting of microorganisms and their by-products,including dead or live bacterial,fungi,viruses,pollen,bacterial endotoxins,mycotoxins,and so on.Aerodynamic diameters of bioaerosol are between 0.1-100m,which means bioaerosol can be inhaled into human's respiratory track,causing infectious diseases and respiratory system disease like hypersensitivity;infections,asthma,lung disease.Bioaerosol samplers are used to verify and quantify the presence of bioaerosols for air quality monitoring and air pollution control.For normal sampling methods like impacting method and impingement,the velocity of air flow is too fast that can damage the microorganisms and affect efficiency.Electrostatic precipitator(ESP)is a popular bioaerosol sampling technology,the impact velocity towards the collection medium is relatively low and collection efficiency is higher.Electro-cyclone performed well especially for capturing small particles,so that it can be designed for bioaerosol sampling.In this paper,two different sampler is designed and tested by Electrical Low Pressure Impactor(ELPI)and used for bioaerosol sampling.The total collection efficiency of electro-cyclone designed was 88.3%and cut-size was 1.98[im when the flowrate was 60 L/min,without electric voltage.The results tested by ELPI conformed Barth model;the collection efficiency increased when with electric voltage,and total efficiency was 96.2%when the applied voltage was-16 kV,7.9%higher than without electric voltage;Total collection efficiency was 76.6%without electric voltage and was 96.3%with-10 kV voltage applied when flowrate was 40 L/min.Although collection efficiency was high,but wall loss cannot be estimated.Bioaerosol experiments showed electro-cyclone was not an ideal sampler for bioaerosol sampling,not as good as liquid impingent.Experiments tested the influence of corona intension on electric charges and survival rate of microorganisms.It proved that electric charges increased when corona intension increased,and survival rate decreased.Then the voltage applied for pre?charge increased from-2 kV to-6 kV,the charges of each grade of Candida albicans(C.albicans)increased 1.8-4.3 times,the survival rate decreased from 98.9%to 48.9%,and the charges of each grade of Escherichia coli(E.coli)increased 1.6-3.2 times,the survival rate decreased from 99.1%to 84.3%.For ESP sampler,collection efficiency for C.albicans aerosol was 63.8%in natural charge condition,76.5%when voltage applied in pre-charge was-6 kV;collection efficiency for E.coli aerosol was 49.7%in natural charge condition,86.4%when voltage applied in pre-charge was-6 kV.In this condition,ESP sampler can be used for environmental bioaerosol sampling.