The Mechanism Study On Controlling Biofilm And Legionella By Electrochemical Technology

Recently, with rapid development of cities in our country, advanced facilities create favorable conditions for reproduction of Legionella, although they provide suitable life for people. More and more chances for people access to Legionella in modern society. Legionella has very close relationship with water. Now, it is increasingly recognized that the seizure of Legionnaires' Disease is not only because of the problem of air-conditioning system, but also the problem of the water system. When the water system which is closely related to human life was polluted by Legionella, it would lead to the outbreak of Legionnaires' disease.The common methods used to control Legionella, such as chlorine disinfection,Copper-silver ionization, ozone disinfection, ultraviolet (UV) disinfection and so on, all have various of limitations, which are mainly caused by Legionella's parasitical habit in aquatic bacteria, protozoan and biofilm besides its own characteristic. Electrochemical technology is a brand-new water treatment technology. In recent years, electrochemical technology for water disinfection has undergone considerable development. The applications of the technology have also been involved into many fields. Studies show that electrochemical technology with multiple disinfection mechanism can not only effectively control the formation of biofilm, but also has continued disinfection effect. Practice also shows that it is very economical and efficient to use this technology for water sterilization and disinfection.The research applies the electrochemical technology of sterilization and disinfection into Legionella control, which opens up new ways for Legionella control. In addition, the mechanism studying and action regularity exploring of Legionella control by electrochemical technology will also provide theoretical basis for application and promotion of this installation in real life.In this paper, controlling Legionella by electrochemical technology wasinvestigated from two aspect of biofilm and Legionella microstructure respectively. The study include:First, Legionella can survive in the biofilm, which makes it protected by biofilm and results in undesired results by traditional disinfection measures. Therefore, the study on controlling biofilm and bacteria by electrochemical technology was carried out from the perspective of environmental factor at first.Second, from the micro-perspective, the experiments using three different methods of electrochemical methods, chlorination disinfection, Fenton reagents, were carried out to investigate the bactericidal efficiency and Legionella surface structure changes with scanning electron microscopy (SEM) after treating by different methods for a period of time.The study reached the following conclusions:K It is efficient to control biofilm and bacteria in the simulated recirculation water system by electrochemical technology.a) Removal ratio of biofilm were 42.7% under the testing condition of 5mA/cm2 and 76.05% under the testing condition of 20mA/cm2 respectively.b) During the treating process by electricity, total bacterial count was monitored every day. The total bacterial count was increasingly decreased down to 25ml"1 after treating for 72h. Meanwhile, It showed opposite trends in the blank comparison experiment, in which the total bacterial count is increasingly increased.2> The observation of Legionella micro-surface structure suggested that the result of electrochemical disinfection is obviously different from that of chlorination disinfection, but similar to that of Fenton regent disinfection. Thus, it is suggested that the mechanism of electrochemical disinfection of Legionella is different from single chlorination disinfection. In the process of electrochemical treatment, chemical products with an oxidizing power are produced, which has much stronger disinfection effect than that of chlorine disinfection.