Quantitative and diversity analysis of DNA accumulation on in-use HVAC filters from tropical buildings
Date of Issue2017-03-29
School of Civil and Environmental Engineering
NTU and Berkeley Education Alliance for Research in Singapore (BEARS)
Buildings are built for human activities. The development of a smart building system should pay equal attention to the well-beings of the human occupants. Ventilation/Heating Ventilation and Air Conditioning (HVAC) system filter is the first line of defence in occupant protection which keeps the indoor environments safe from potential airborne pollutants. This thesis focuses on the analysis of biological material accumulated on functioning HVAC filters and attempts to discern whether the results can be a good representatives of indoor air quality. This thesis consists of three major parts; the method optimization, the cross-sectional HVAC filter study and the longitudinal HVAC filter study. The method optimization part focuses on maximizing the biomass yield from a given environmental samples, namely our HVAC filter samples. We found that adding additional cell lysis, particularly high temperature water bath sonication could increase the biomass yield considerably. Our work has also proposed a concentration approach in the middle of the extraction step which can be used in series with the additional sonication, minimizing time and possible DNA loss. With our optimized protocol, we analysed a set of HVAC filters serving separate, well-characterized indoor environments (cross-sectional study). Our findings confirm that different indoor conditions such as occupancy level and the function of the indoor environment are well reflected in both the absolute and relative abundances of certain bacteria and fungi on HVAC filter. While there are still factors to be considered, these findings support the application of HVAC filters as an indicator of indoor environmental quality. The final part (longitudinal study) focused on one air handling unit filter. We investigated how the biomass accumulate on the filter during its operation time. Based on the microbial community analysis, fungal DNA on the filters was found to mainly originate from the outdoor air intake, while the bacterial DNA originate from the indoor sources. In addition, the biomass accumulation profile revealed that there is a loss rate for certain biomass already trapped on the filter. This finding indicates that an interpretation of biomass concentration based on HVAC filter sampling must be completed with its corresponding meta-data.
DRNTU::Engineering::Environmental engineering::Environmental pollution