Study On Treatment Of High Arsenic And Fluorine Groundwater By Sand Filtration-Nanofiltration Process

The population of villages and towns in China accounts for more than half of the country's total population.The drinking water source of village residents is mainly from groundwater.The pollution of fluoride and arsenic ions in groundwater in some areas has caused great threats and serious impacts on people's health and life activities..In recent years,the incidence of various types of diseases caused by water safety,especially over-standard arsenic and fluoride drinking water,has increased significantly.Food safety and drinking water safety have received increasing attention.In order to solve this serious problem,this experiment uses sand filtration and nanofiltration technology to study the feasibility of simulating high arsenic and fluoride groundwater purification,and explores the best process parameters and the mechanism of sand filtration and nanofiltration to remove arsenic and fluorine.The specific research results are as follows:?1?In the process of removing high-fluorine groundwater by sand filtration,the filling ratio and arrangement mode of the filter material,the injection speed of the dynamic sand filter column,the initial concentration of fluoride ion,the series connection of the filter column,the pH of the water and other factors were investigated.The effect on the removal of fluoride ions.The experimental results show that the filling method of the three-layer filter material with segmental layer filling has higher fluorine removal efficiency,and the removal effect of single filter material is manganese sand>quartz sand>iron powder.The filtration rate of the fluoride ion was investigated by a filter column device filled with three layers of filter material,and the filtration rate was 1.2 m/h,the fluoride ion concentration of the raw water was 15mg/L,the pH was 8.0,and the two filter columns were connected in series.The removal efficiency of fluoride ion under process conditions can reach 97.1%,reaching the national drinking water standard.?2?In the study of fluoride removal by nanofiltration process,the operating pressure,the influent water sample temperature,the water sample pH,the influent concentration of the fluorine-containing water sample,and the influent concentration of the fluoride-containing water sample were investigated by single factor experiments.The effects of coexistence of inorganic salt ions and natural organic matter on the removal of fluoride ions.Using the response surface method to optimize the operating pressure,the influent water sample temperature and the water sample pH,the optimal process parameters were obtained,namely:the pressure was 0.28 MPa,the raw water pH was 8.5,and the temperature was 22�C.Under this condition,When the fluoride ion concentration of the influent water sample is 12 mg/L,the removal rate of fluoride ion can reach over 94%,and the water quality condition meets the national drinking water standard.?3?In the study of the removal of As³⁺and As⁵⁺by nanofiltration process,the parameters of the membrane device during operation were investigated,including:initial concentration of arsenic,influent pH,membrane operating pressure and so on.The results show that the removal efficiency of As⁵⁺is much larger than that of As³⁺.The alkaline condition is beneficial to the removal of As³⁺and As⁵⁺.The removal efficiency of As⁵⁺increases with the increase of pH,while the removal rate of As³⁺is relatively slow.As³⁺removal rate decreases with increasing concentration,while As⁵⁺removal rate increases with increasing concentration;As³⁺and As⁵⁺removal during pressure increase from 0.1 Mpa to 0.6 Mpa The rate showed a decreasing trend,and the removal rate of As³⁺decreased more obviously.?4?In the process of removing high arsenic groundwater by sand filtration,the effects of the injection speed of the sand filter column,the initial concentration of arsenic ions and the pH of water on the removal of arsenic ions were investigated in turn,and the arsenic removal by sand filtration was optimized.Process parameters.The results show that the removal efficiency of As³⁺by sand filtration is higher than that of As⁵⁺.In the process of filtration speed increasing from 0.4 m/h to 2.0 m/h,the decline trend of As³⁺and As⁵⁺is basically the same,and the removal rate of As⁵⁺is 94.9%.Decrease to 92.5%,the removal rate of As³⁺decreased from 96.3%to 94.3%,both of which decreased by about 2%;under acidic conditions,the removal rate of As³⁺and As⁵⁺by sand filtration was lower,under neutral and weak alkaline conditions.The removal rate was higher.When the pH was 8,the removal rates of As³⁺and As⁵⁺were the highest,which were 96.2%and 94.9%,respectively.The removal rate of arsenic decreased under strong alkaline conditions.With the increase of the total amount of effluent,the effluent concentration of arsenic gradually increased.In the range of 4�20 L of total effluent,the effluent concentration of As³⁺increased slowly compared with As⁵⁺.When the total effluent exceeded 20 L,the As³⁺effluent concentration The increase is more pronounced than that of pentavalent arsenic.?5?The effluent quality of the fluorine-containing groundwater treated by sand filtration or nanofiltration can reach the national drinking water standard,and the single process can not meet the standard for the treatment of high arsenic groundwater.Therefore,the sand filtration-nanofiltration combined process is adopted to treat high arsenic.groundwater.The sand filtration-nanofiltration combined process is more efficient at removing arsenic than a single process.When the arsenic concentration in the influent water sample is 400?g/L,the combined process can reduce its concentration to about 1 ug/L,which meets the national drinking water standard.In summary,through the optimization of process parameters,a single process of sand filtration or nanofiltration can make the effluent water with an initial concentration of fluoride ion of 12 mg/L reach the national drinking water standard.In the sand filtration-nanofiltration combined process,the removal of arsenic from high arsenic groundwater is more efficient when the arsenic concentration of the influent water sample is 400?g/L.It is proved that sand filtration or nanofiltration sand has high feasibility for the treatment of high fluoride groundwater.The combination of sand filtration and nanofiltration is a feasible arsenic removal process.It provides a new solution to the treatment of high arsenic and high fluoride waters in Xinjiang.