Effects Of Transfered Ozone Dose And Claimed Water Quality On Ozone Disinfection Characteristics

Water reuse is an important way to meet the shortage of water resource in China, and how to ensure the security of water quality is one of the key problems of this process. Ozone as a kind of a broad spectrum of efficiency and clean sex disinfectant can disinfect pathogenic microorganisms, and remove the organic and inorganic pollutants in water. But two main technical problems lay in the ozone disinfection process. The first one is the choose of optimum ozone dosage, and the second one is the effect of quality of reuse water. Hence, taking the actual reuse water of many sewage treatment plants in Beijing as example, this paper investigated the influence of TOD, that’s transferred ozone dose, to the inactivation rate of pathogenic microorganisms using static overpressure test device, which provided a theoretical support for the selecting of the best TOD. By statistical analysis, this paper was seeking for water quality index which have distinguished correlation with the inactivation rate of pathogenic microorganisms, and established pertinence between water quality index and microbial index. Meanwhile, taking the water sample after the separation of the molecular weight as the example, this paper was seeking for substance which greatly affected the inactivation rate of pathogenic microorganisms. The results are as follow:TOD was a vital factor which strongly affected the inactivation rate of pathogenic microorganisms. The reduction rate of Escherichia coli can be divided to slow-reduction-phase and rapid-reduction-phase with the change of TOD. When TOD is less than TODlow(that is the turning point of slow-reduction-phase and rapid-reduction-phase), the ascension of reduction rate of Escherichia coli is slow. While the TOD is more than TODlow, the ascension escalated rapidly. The reduction rate of Bacillus subtilis spores can be divided to lag phase and rapid-reduction-state with the change of TOD. When TOD is less than TODlag (that is the turning point of lag phase and rapid-reduction-phase), the inactivated rate of Bacillus subtilis spores is not eminent. While TOD is more than TODlag, the reduction rate of Bacillus subtilis spores surged with the increase of TOD.The experiential value of TODlow in the actual reuse water of many sewage treatment plants in Beijing was3-4mg/L, and the experiential value of TODlag Was2～6mg/L.The required TOD to reach the same reduction rate for pathogenic microorganisms differed under different water quality. The required TOD to reach21og for the reduction rate of Escherichia coli and BSS in the actual reuse water of many sewage treatment plants in Beijing were3mg/L-6mg/L and8mg/L-18mg/L respectively.UV254and total fluorescence intensity were intuitional water quality index which correlated with the inactivation rate of pathogenic microorganisms. Under same operational condition, with the increase of influent UV254and total fluorescence intensity, the inactivation rate of pathogenic microorganisms were getting worse. The relationship between the reduction rate of UV254and inactivation rate of Ecoli. showed an exponential function which is y=0.12e0.06x, and the relation coefficient is0.80. So did the reduction of total fluorescence intensity. While the exponential function is y=0.03e0.06x, and the relation coefficient is0.79. When all the reduction rate of UV254, total fluorescence intensity and the inactivation rate of BSS were increased, the first one and the third one showed obvious linear relationship which the relational function is y=0.06x-2.5, and the relation coefficient is0.70. While the total fluorescence intensity and the inactivation rate of BSS showed some kind of linear relationship, and the relational function is y=0.12x-8.64, and the relation coefficient is0.57. This method can not only greatly simplify the workload of experimental research or engineering practice, but also can easily implement real-time online monitoring of inactivation.Color can be used as an indicator during ozone disinfection process. The required TOD when the color removal reached stable state with the increasing of TOD can be taken as the best reference of TOD. Only when the TOD is more than the best reference of TOD can the pathogenic microorganisms get into rapid-reduction-phase.The water quality of reuse water can not only affect the inactivation rate of ozone to pathogenic microorganisms, but also have significant influence on the properties during the process of inactivation of pathogenic microorganisms.The more content of organic matter in reuse water, the less inactivation rate of pathogenic microorganisms, the more TOD required for pathogenic microorganisms getting into rapid-reduction-phase, the slower ascension of inactivation rate of Ecoli with the increasing of TOD.The organic matter in the actual reuse water were mainly molecular weight<1kDa and1k-lOkDa components. The organic matter which has1k-10kDa molecular weight was the main substance affect ozone disinfection effect in actual reuse water. In the future ozone disinfection process, we can consider implement membrane treatment processes to reuse water before disinfection, then remove macromolecule organic matter from reuse water to achieve higher disinfection under lower TOD.