Iranian environmental engineers studied the performance of zinc oxide nanoparticles in photocatalytic disinfection of microbial pollutions from aqueous media. Iranian environmental engineers studied the performance of zinc oxide nanoparticles in photocatalytic disinfection of microbial pollutions from aqueous media. The removal of microorganisms by using nanoparticles in the presence of UV, which has applications in food and medical industries, drinking water, and environmental industries, has higher performance than the removal method by using only UV. Dr. Mohammad Yousef Alikhani, a member of the Scientific Board of Hamedan University of Medical Sciences, explained about the research, and stated, “The most important objective in this research was the study the kinetics of the removal of Escherichia coli process in the designed reactor. According to the experiments, the reaction was determined to be first degree.” Results of the research showed that the efficiency of the method increased as the concentration of nanoparticles increased. The reason was the increase in the surface of catalyst and also the free electrons created by nanoparticles. The same result was obtained for contact time and the initial concentration of bacteria. The optimum condition of pH value of the media was reported neutral pH, because the performance of the photocatalyst decreases at acidic or alkaline environment. According to Dr. Alikhani, the performance of UV/zinc oxide process in the removal of Escherichia coli significantly increased in comparison with that of purification process by using UV due to the smaller size and higher surface area of the modified nanoparticles. Therefore, a simultaneous process of UV/zinc oxide nanoparticles can be used as an effective method in the disinfection of microorganisms from aqueous solutions. Results of the research have been published in details in Water Science & Technology in February 2013, vol. 67, issue 3, pp. 557-563.