Fabrication Of Photocatalytic Disinfection Device And Its Wastewater Treatment Performance

Disinfection technology is an essential step for wastewater treatment process. Recently, ultraviolet(UV) disinfection is widely used for wastewater due to the broad-spectrum antiseptic property, no disinfection by-products and rapid disinfection. UV disinfection can prevent DNA from replicating properly to inhibit the microbial growth, but can’t kill microorganisms completely. The microorganism treated by UV disinfection process can restore the ability to reproduce, and then threaten the water security. In order to avoid the potential risk, the microorganism must be exterminated thoroughly. The·OH radical generated by photocatalytic process can destroy cellular structure completely, then completely kills the microorganisms. However, most reported photocatalytic devices are sequencing batch reactors, and the capacities of each unit disposal are usually several liters per hour, In order to treat with mass wastewater, unit array configurations located in large areas are needed, which is difficult to be practice applied. To fabricate a continuous-flow photocatalytic reactor to improve the handling capacity is the key to solve the problem. The thesis works are carried out for the above problems, and the main contents are as follows:(1) The fabrication of the photocatalytic reactor with a capacity of 100-litre per hour and its disinfection performance.In order to explore the rational structure of the pilot-scale photocatalytic disinfection device and shorten the test cycle, we designed and fabricated a miniature continuous-flow photocatalytic reactor with a capacity of 100-litre per hour. The reactor shell was stainless steel cylinder which had the inner diameter of 63.5 mm, the UV lamp was put on the axis location of the reactor shell, and the platy support coated with TiO2 via sol-gel method was radially arranged around the UV lamp. In the disinfection experiment, the E. coli concentration of the effluent treated by the photocatalytic disinfection reactor was 80%of that treated by UV disinfection process which was used as control group. In the E. coli resurgence evaluation experiment, after being cultured for 16 hours, the E. coli concentration of the effluent treated by UV disinfection increased to 7.70×10~6 CFU/mL. In contrast, after being cultured for the same time, the E. coli concentration of the effluent treated by photocatalytic disinfection process was only 1.02×10~6 CFU/mL (13.25%of the UV disinfection process). The results showed that the abilities of rapid sterilization and inhibiting the microbial resurgence improved obviously compared with the UV disinfection process.(2) The fabrication of the photocatalytic disinfection device with a capacity of 24-ton per day and its disinfection performance.According to the experience above, we designed a helical structure support which had a better mass transfer performance, and sprayed the P25 photocatalyst on the surface of the support via the electrostatic spraying technology, the photocatalyst support was put into the stainless steel cylinder which had a diameter of 81 mm, wrapping around the UV lamp. The photocatalytic disinfection device with this structure had a capacity of 24-ton per day, which reached the pilot scale. The results of the disinfection performance of the device showed that the E. coli concentration, the degrees of photoreavtivation and dark reactivation phenomena of the effluent treated by photocatalytic disinfection process were 33.54%,2.71%and 2.67% of the UV disinfection process, respectively. Based on this, we examined the withstand shock loading of the device by regulating flow(0.5 t/h-1.8 t/h) and E. coli concentration (2.76×10~3 CFU/mL-4.80×10~7 CFU/mL), the result showed that the disinfection effects were better than the UV disinfection process in the test range. We further used phage f2 as the target microorganism to simulate the disinfection performance of virus. The result showed that the phage f2 logarithm inactivation value of the device reached up to 6.37.(3) The improvement of the photocatalyst support and calculation of the operation cost.TiO2/Ti compound photocatalytic materials were prepared by sol-gel method. The result showed that the surface morphology of the composite material didn’t change apparently after being scoured for 48 h. The result of the equipment running showed that the performance of the device was stable after using the composite material. The computational result of the equipment operation showed that the cost of the device was 1.07 yuan per ton.