Steam inactivation of vegetative bacteria in ventilation air

Open Access
Nookong, Mookarin
Graduate Program:
Agricultural and Biological Engineering
Master of Science
Document Type:
Master Thesis
Date of Defense:
May 05, 2012
Committee Members:
  • Virendra Puri, Thesis Advisor
  • Ali Demirci, Thesis Advisor
  • Savas Yavuzkurt, Thesis Advisor
  • Steam
  • Inactivation
  • vegetative bacteria
  • ventilation
Steam, made from abundant supply of clean water, is an inexpensive and thermally rich carrier of energy with the potential to deactivate the pathogens that are released in the ventilation air from the facility utilizing pathogens such as research environment. Air decontamination is required only for research facilities which contain an excessively high concentration of pathogens that has been added to the environment. This is a study to find the appropriate air flow and optimal residence time through the reactor and the optimal amount of steam that need to be injected into the system. In order to deactivate the pathogens, a six-baffled ventilation air decontaminant reactor system was designed and fabricated. While steam is injected into the air decontamination system, air flow rate was used as input to develop a mathematical model for predicting the optimum setting for the ventilation system with R2 of 96.1%. Using E. coli K12 as the microorganism in this research provides the basis for the mathematical model to determine the reference temperature (54.6 C), z-value (5.5 C) and D-value (161sec). This relationship is for predicting the accumulated population fraction with 95.6% coefficient of determination (R2). The relationship of steam flow rate that is needed to achieve a given log reduction of pathogens (y) is exponentially related ( ) to the inlet temperature (x) with 99.9% coefficient of determination (R2). The residence time in the ventilation system ranged from 27.68 sec to 31.33 sec with the constant air flow rate of 0.024 m3/s. These relationships were used to calculate the flow rate and decontamination rate in research environment using the six baffled system.