Photocatalytic inactivation of bioaerosols by TiO 2 coated membrane

Abstract

Indoor air pollution by microbial contaminants is increasingly receiving attention as a public health problem. Under a suitable environment, such as in heating, ventilation and air conditioning (HVAC) system, airborne bacteria are able to proliferate and grow causing various allergies and illnesses. This can be particularly serious in tropical regions due to high relative humidity and warm temperatures all round the year. Application of photocatalysis using UV-A and TiO 2 to inactivate air-borne bacteria is relatively new and systematic parametric study is required for the engineering design of a process based on this technology. This study investigates the effects of TiO 2 mediated inactivation of various bacterial species in batch and continuous systems using different TiO 2 loadings and radiation intensities. Gram-negative bacteria, E. coli and two Gram-positive bacteria, Microbacterium sp. and Bacillus subtilis were used for the inactivation studies. In both systems, inactivation rates of Gram-negative E. coli are higher than the Gram-positive Bacillus subtilis and Microbacterium sp. and the inactivation rates increased in presence of TiO 2 for all bacteria. Depending on the type of bacteria, TiO 22 loading and light intensity, an increase of 1.3-5.8 times in the inactivation rates was obtained from those in the absence of TiO 2. The inactivation rates in the batch and continuous systems were reasonably comparable. Inactivation rates in the continuous system are somewhat higher than those in the batch system due to the unaccounted loss of bacteria via adsorption and settling on the reactor walls in the flow system. The study demonstrates an approach that can be used for the designing of large scale systems for the treatment of bioaerosol.