| The drinking water of alpine pastoral areas seriously exceeds the standard,and the direct drinking of untreated river water by herders will cause acute diarrhea,vomiting,parasitic infections and other diseases,which poses a serious threat to the health of herders.In order to ensure the safety of herdsmen’s water and consider the convenience of herdsmen’s transfer,ultraviolet disinfection is a necessary choice for water treatment equipment in alpine pastoral areas.UV disinfection has the advantages of high sterilization efficiency,wide range of application,no harmful disinfection by-products,low cost,no pollution,simple equipment,and no consumption of chemicals.But so far,China’s ultraviolet disinfection equipment manufacturers are imitation foreign disinfection equipment manufacturing,lack of basic theory and technical support,disinfection effect can not be guaranteed.In this project,the disinfection efficiency of disinfection water tanks and overflow ultraviolet disinfection reactors is studied.For the disinfection water tank,this paper mainly studies the water quality factors affecting the UV illuminance,and first finds the water quality indicators that affect the UV illuminance through the single-factor influence UV illuminance experiment.Then use the experimental design software(design expert software),design the response surface experiment according to the Box-Behnken experimental design principle,and establish a mathematical model of the influencing factors of ultraviolet illumination with ultraviolet illuminance as the response value,which provides theoretical support for the design of disinfection water tank.For the overflow ultraviolet disinfection reactor,this paper uses the commercial overflow ultraviolet disinfection reactor as a template,based on computational fluid dynamics technology(CFD technology),establishes a suitable ultraviolet disinfection CFD model,and simulates the internal flow field,ultraviolet illuminance and effective ultraviolet dose of the reactor to study the influence of the flow field on the effective ultraviolet dose of the ultraviolet disinfection reactor.Moreover,the effective UV dose of the commercial UV disinfection reactor simulation calculation results was verified and the parameters were modified by the biological verification method,so that the effective UV dose of the simulation results was in line with the actual working conditions.Due to the poor coupling of the flow field and UV illumination distribution of commercial UV disinfection equipment,the structural parameters of the commercial UV disinfection reactor(adding transverse baffle,deflector,longitudinal baffle,changing the position of the inlet and outlet)were optimized,and the effective UV dose of the simulation calculation result was used as the index,and the UV disinfection reactor was compared to obtain an ultraviolet disinfection reactor with the best disinfection efficiency.The following are the main conclusions of this article:(1)The factors affecting ultraviolet illumination are:distance from lamp(A),permanganate index(B),turbidity(C),trivalent iron ion concentration(D),and the order of the influence of ultraviolet illuminance is:distance to lamp>permanganate index>ferric ion concentration>turbidity;(2)Quadratic regression equation of underwater ultraviolet illuminance of 8W ultr aviolet lamp:Y=9.82A~2+1.68B~2+0.70D~2+1.40AB+1.50AD+0.69BD-12.56A-2.63B+0.15C-0.99D+2.29,R~2=0.9909;(3)The distribution of ultraviolet illuminance in the commercial ultraviolet disinfection reactor is uneven,the ultraviolet illuminance decreases with the increase of the distance from the lamp,and the weakest ultraviolet illuminance at the bottom of the lamp is only 10 m W/cm~2due to the absence of direct ultraviolet light;The flow rate distribution in the commercial ultraviolet disinfection reactor was uneven,and the fluid flow rate of 0.05 m/s on the same side of the water inlet was less than that of 0.12 m/s on the opposite side of the water inlet,but the ultraviolet illuminance distribution was the same,resulting in the effective ultraviolet dose on the same side of the water inlet being greater than that on the opposite side of the water inlet.(4)The simulation calculation and verification experimental results show that the effective ultraviolet dose of the commercial ultraviolet disinfection reactor decreases with the increase of the inlet flow rate;The verified ultraviolet dose is the same as the simulated ultraviolet flux with the flow rate,and the effective ultraviolet dose calculated by the simulation is higher than that of the biologically verified effective ultraviolet dose,especially when the inlet flow rate is low.By adding a correction factor to correct the effective UV dose calculated by the simulation,the simulated calculated UV dose can be consistent with the effective UV dose actually bioverified.(5)The minimum ultraviolet dose of the commercial ultraviolet disinfection reactor is 55m J/cm~2,and the minimum ultraviolet dose of the reactor reaches 60 m J/cm~2 after setting the spacing of 35 mm transverse baffle;After setting the 0.3 mm deflector,the minimum UV dose of the reactor was also 55 m J/cm~2,but the proportion of particles in the minimum UV dose was less than half that of commercial UV sterilization reactors.After changing to the ipsilateral tangential direction of water inlet and outlet,and setting the baffle spacing of 17.5 mm,the minimum effective UV dose of the reactor reached 70 m J/cm~2,and the lowest UV dose particle was 0.3%;After changing the heterolateral tangent direction to water inlet and out,and setting the baffle spacing of 17.5 mm,the minimum effective UV dose of the reactor also reached 70m J/cm~2,but the lowest UV dose particle was 1%.(6)Water inlet and outlet in the same tangent direction,and the baffle spacing of 17.5 mm is the best structural parameter,under this structural parameter,the lowest effective UV dose of the reactor reaches 70 m J/cm~2,and the proportion of the lowest UV dose particles is very small,0.3%;The design of mobile ultraviolet disinfection equipment with this structural parameter can better ensure the effluent safety of rural small water treatment devices. |
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