The Disinfection Kinetics Of Ozone For Reuse Of Municipal Wastewater

With the economic development and urbanization, water shortage is becoming more and more serious. The reuse ef wastewater is an important way to solve the problem. The processes of disinfection play a key role in wastewater reuse. This article made a deep study of the processes of ozone dissolution , decomposition and disinfection in secondary effluent of municipal water using semi-batch reactor and pilot reactor. The experiment results indicated :(1 )In the semi-batch reactor, ozone concentrations in the secondary effluent are proportional to the time of gas supply. The dissolving efficiency of ozone is decreasing with the increasing gas flow and pH and the pH is more important than gas flow. The ratio coefficient K0ranged from 0.3221 to 0.3488 when the gas flow is between 5 and 301/min and the values of pH is between 7.2 and 7.4, and 0.4376~ 0.1525 when gas flow is 101/min and values of pH are between 6.6 and 9.0.(2)The decomposition rates of ozone are pH related. The pH is higher, the rates are greater. If the values of pH are between 7.2 and 7.4, the kinetic equations in the semi-batch reactor and in the pilot-reactor are the same. The decomposition processes are in first-order and the constant is ki=0.192min-1.(3)The ozone concentrations in the column-reactor were affected by the direction of flow. At the same flow rate, the concentrations of ozone in upflow are higher than that in downflow at the same HRT.(4)In the semi-batch reactor, the results of ozone disinfection are acceptable.When the gas flows are larger than 101/h and pH between 7.2 and 7.4,the inactivation ratios of Coli. are higher than 99.9% and the concentrations are lower than 1000cfu/1 after 10mins .This would be satisfied with the quality standard of the reuse water. Under these circumstance the dynamic equation is - log S = Kt. While the values of pH are between 6.1 and 6.6, the standard is reached after Smins when the flow rates are higher than 101/h.fT' the pilot-reactor, the flow rates of water affect the ozone disinfection strongl) and the rates are larger and the efficiency is better. In the downflow, the treated water would be satisfied with the standard when the rates are larger than 30.71/min. The flow direction of water in column reactor affects the disinfection results too. The standard would be reached when the rates are larger than 30.71/min in downflow while it is 181/min in upflow.(6)In the pilot-reactor, the Venturi-mixed reactor can improve the ozone-water mass transfer effectively. The efficiency of ozone dissolution and the disinfection are increasing with the increase of water flow rate when it ranges from 12.81/min to 30.71/min.(7)There are some capacity of surplus disinfection in the secondary effluent treated by ozone and more than 35 percent of the Coli. mixed with the untreated water are inactivated.This article is creative and these results can be used in practice design.