Study On The Treatment Of High-salt And High-organic Wastewater By Ultraviolet/Ozone Process

The discharge of wastewater with high salts and organic content is considerable in China,especially textile and pesticide wastewater.Ozonation widely applied to the degradation of refractory organic matters.However,the low solubility and stability of O3 in water and the selective removal of organic matters inhibit the utilization of ozonation process.Therefore,based on the research status at domestic and foreign as well as the prospects of practical application,the combined process of low-pressure ultraviolet mercury lamp(UV)and O3 was used to treat wastewater with high salts and organic content.UV/O3 process can improve the efficiency of O3 utilization and generate multitudinous types of reactive oxygen species(ROS)to accelerate the degradation efficiency of organic pollutants.In addition,as a new type of UV light source,ultraviolet light emitting diode(UV-LED)has the advantages of wavelength settable,low energy consumption,mercury-free,compact structure,durability,no need for stability time,etc.,which can reduce the cost of wastewater treatment and improve the convenience of its application.UV-LED addresses the deficiency of mercury vapor UV lamps in water treatment and it could be used as the alternative instead of conventional mercury UV lamps.Finally,the UV/O3 process is applied to the pilot-scale treatment of actual textile wastewater.The pilot-scale equipment for the UV/O3 pressurization process was designed,improving the solubility and the utilization rate of O3.The effect of UV/O3 pressurization process and Fenton oxidation process effluent no RO membrane fouling and effluent quality was further compared.That process was no secondary pollution and has a wide application prospect in the waterwater treatment.The major research contents and conclusions of that paper are as follows:In UV/O3 process,under conditions of high salinity,high pH and UV irradiation,O3 has high mass transfer coefficient(kLa)and self-decomposition(kd),which further improved the utilization efficiency of O3 and the formation of ROS for the degradation and mineralization of RB.The 1O2,O2·-and OH played indispensable roles in the TOC removal of RB in both O3 and UV/O3 processes.UV-LED with four wavelengths(i.e.,255,265,280,and 310 nm)was employed to activate O3 for the treatment of hexazinone wastewater.The removal efficiency of hexazinone was highest in UV-LED(280 nm)/O3 process,and the kLa kd were also highest at 280 nm.·OH and O2·-were dominant ROS for the degradation of hexazinone in the UV-LED/O3 system,and the 1O2 also played a positive role for the degradation of hexazinone.Toxicity predication suggested that most by-products were similar or less toxic to hexazinone in salt-free consition,but the biotoxicity of the hexazinone degradation products was increased in high-salt consition.Besides,UV-LED could make up for the deficiency of traditional UV lamp,and has a good application prospectUV/O3 pressurization process was applied to the actural textile wastewater pilot scale treatment.Compared with ozonation alone process,the decolorization and CODcr removal efficiency of actual textile wastewater were improved by UV/O3 pressurization process.The solubility of O3 and the efficiency of gas-liquid mass transfer rate were also enhanced in UV/O3 pressurization process,so as to improve the treatment capacity of actual textile wastewater.In UV/O3 pressurization process,the RO membrane pollution could be alleviated to some extent,while RO membrane was blocked seriously by Fenton oxidation effluent.The calcium salt was the major substances that caused membrane pollution.No other chemicals are added during the UV/O3 pressurization process.A large number of iron salt,waste acid and lime milk were added in Fenton process to participate in the reaction,aggravating the pollution of RO membrane.In addition,the effluent quality of UV/O3 pressurization process is better than that of Fenton oxidation process.