Control of Bioaerosols by Nanosilver Particles/Clay Modified Filter in Indoor Environment
Date Issued
2015
Date
2015
Author(s)
Chen, Kai-Jie
Abstract
Bioaerosols is one of the concerning topics associated with indoor air quality control. The combination of indoor HVAC system with filtration device is the most common bioaerosol control technology. In order to inactivate bioaerosols, clay-supported silver nanohybrids (AgNP/Clay) could be immobilized on the filter to form an antimicrobial filter by utilizing its characteristics of high antimicrobial activity and low cytotoxicity. According to the results of continuous flow filtration test for four types of filers(un-modified filter, AgNP/Clay modified filter with 12.6ppm, 31.5ppm, and 63ppm Ag), the filter efficiency for E.coli was increased 13.7~19.9% and 14.0~19.9% due to the decreased in porosity at RH=30% and RH=70%, respectively. However, there was no significant difference between un-modified and modified filter for yeast could be observed. According to the results of statistical analysis of modified filters with different AgNP/Clay concentrations, the P-value was greater than 0.05, which indicated that there was no significant difference between filtration efficiency. By observing the survival of microorganism on filter, the results showed that modified filter with higher concentration of AgNP/Clay had better antimicrobial performance. In HVAC filter testing simulation system, both the survival number of E.coli and yeast had no significant decrease after the installation of filter under environmental condition of RH=30%. Bioaerosols had difficulty to remove from HVAC system due to the differential pressure produced from the installation of filter, which result in deficiency of recirculation rate of HVAC system. Under environmental condition of RH=70%, the reduction rate of E.coli and yeast increased 1.0~10.8% and 17.7~31.0%, respectively. However, there were no remarkable difference between un-modified and AgNP/Clay modified filter. It could be observed that E.coli were rare to survived on filter after the filtration of HVAC system while survival rate of yeast on un-modified filter was much higher than AgNP/Clay modified filter. It indicates that filter modified with AgNP/Clay has antimicrobial effect. Based on the test of on-site bioaersols at four public locations (classroom, library, dining hall, and out-patient hall), the Ag/NP/Clay modified filter had filtration efficiencies of 98.9% and 98.7% for bacteria and fungi, respectively. Furthermore, according to the results of survival examination of microorganism on filter in classroom with the duration of 12 hours, the survival rates for bacteria and fungi were 290% and 76.5% for un-modified filter while 50% and 25% for AgNP/Clay modified filter, respectively. It could be summarized that AgNP/Clay modified filter has a positive filtration and antimicrobial performance with on-site application.
Subjects
indoor air quality
bioaerosol
AgNP/Clay
filtration
antimicrobial activity
SDGs
Type
thesis
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