The Assessment of Indoor Formaldehyde and Bioaerosol Removal by Using Negative Discharge Electrostatic Air Cleaners.

This study investigated the single-pass performance of a negative corona electrostatic precipitators (ESP) in removing suspended particulates (PM2.5 and PM10), formaldehyde (HCHO), and bioaerosols (bacteria and fungi) and measured the ozone (O3) concentration generated by ESP. The experimental results revealed that if the operational conditions for the ESP were set to high voltage (-10.5 kV) and low air flow rate (2.4 m3/min), ESP had optimal air pollutant removal efficiency. In the laboratory system, its PM2.5 and PM10 removal rates both reached 99% at optimal conditions, and its HCHO removal rate was 55%. In field tests, its PM2.5, PM10, HCHO, bacteria, and fungi removal rates reached 89%, 90%, 46%, 69%, and 85% respectively. The ESP in the laboratory system (-10.5 kV and 2.4 m3/min) generated 7.374 ppm of O3 under optimal conditions. Under the same operational conditions, O3 generated by ESP in the food waste storage room and the meeting room were 1.347 ppm and 1.749 ppm, respectively. The removal of HCHO and bioaerosols was primarily attributed to their destruction in the corona, as well as ozone oxidation, and collection on the dust collection plate.

A Study of Nanosilver Colloid Prepared by Electrical Spark Discharge Method and Its Antifungal Control Benefits.

This is a study of an antimicrobial test, including yeast, Aspergillus Niger, and Aspergillus Flavus, on a nanosilver colloid solution. The antibiosis is compared with a standard silver ion solution at the same concentration as in the experimental process. This study proved that the nanosilver colloid prepared by the electrical spark discharge method (ESDM) is free of any chemical additives, has a microbial control effect, and that the effect is much better than the Ag+ standard solution at the same concentration. 3M Count Plate (YM) is used to test and observe the colony counts. The microbial control test for yeast, Aspergillus Niger, and Aspergillus Flavus is implemented in the nanosilver colloid. In addition to Aspergillus flavus, an Ag+ concentration of 16 ppm is enough to inhibit the growth of the samples. At the same concentration, the nanosilver colloid has a much better microbial control effect than the Ag+ standard solution, which may be because the nanoparticle can release Ag+ continuously, so the solution using the ESDM has a more significant microbial control effect.

The Study of an Ultraviolet Radiation Technique for Removal of the Indoor Air Volatile Organic Compounds and Bioaerosol.

This study examined the use of high dosages of ultraviolet germicidal irradiation (UVGI) (253.7 nm) to deal with various concentrations of air pollutants, such as formaldehyde (HCHO), total volatile organic compounds (TVOC), under various conditions of humidity. A number of irradiation methods were applied for various durations in field studies to examine the efficiency of removing HCHO, TVOC, bacteria, and fungi. The removal efficiency of air pollutants (HCHO and bacteria) through long-term exposure to UVGI appears to increase with time. The effects on TVOC and fungi concentration were insignificant in the first week; however, improvements were observed in the second week. No differences were observed regarding the removal of HCHO and TVOC among the various irradiation methods in this study; however significant differences were observed in the removal of bacteria and fungi.