Study On The Application Of Seawater Desalination For Drinking Water

In recent years,seawater desalination plays an important role in drinking water.Compared with other technologies,electrodialysis desalination technology has the advantages of convenient operation,convenient maintenance,long service life and corrosion resistance.Electrodialysis is expected to replace reverse osmosis in small,dispersed water desalination supplies.This study have compared the effect of desalination under the different operating conditions such as voltage,current,initial concentration and flow velocity,and determines the best operating process conditions.The performance of seawater desalting by ion-exchange membrane was compared and the standard of selecting ion exchange membrane was established.1.Optimization conditions of electrodialysis processThe effects of different current,voltage,concentration and initial concentration on the desalting process of seawater were compared,and the optimum operating conditions were determined.(1)The increase of initial concentration,energy consumption per unit volume of drinking water was increased,the water from dilute chamber to concentrate chamber increase,when the concentration difference reached above 20000 mg/L,this phenomenon is more pronounced;(2)The initial concentration of dilute and concentrate chamber increase,the resistance of membrane reactor decrease.The current efficiency is highest when the initial concentration of the dilute and concentrate chamber is between 6000 and 15000.(3)Under the limit operating voltage,as the operating voltage increase,the efficiency of electrodialysis desalination increase and the volume of water transfer increase.(4)Under the limit current,with the increase of operating current in the electrodialysis desalting process,the desalting rate increase,the water transfer volume increase and the membrane reactor resistance decrease.When operating current is 1.5A the current efficiency is the highest reaching 94%,and 1.5A is the best operating current.The concentration of the initial concentration of electrodialysis desalination process should be controlled between 6000 and 15000mg/L.2.Electrodialysis desalination for seawater with different segments of concentrated water emissionThe experiment compared the influence of five different segments of concentrated water emission to electrodialysis desalination process and determined the best segments of concentrated water emission,the conclusions as following:(1)through the experiment with the increase of the section of concentrated water discharge,desalination rate increase,the water migration quantity from dilute chamber to concentrate chamber has fallen dramatically,reduced 35.4%.As the increase of the segment of concentrated water emission,the electric migration coefficient of ions ? remains the same,the diffusion coefficient of concentration difference of ions ? decrease,the electric migration coefficient of water ? remains the same,the diffusion coefficient of concentration difference of the water ? decrease.(2)With the increase of the section of concentrated water discharge,the resistance of the membrane reactor increased.the current efficiency improved obviously,the efficiency of four segments of concentrated water emission is highest about 96%,five sections began to decline.With the increase of the section of concentrated water discharge the energy consumption decreased gradually,and the energy consumption of the four sections was up to 12KWh/m3,and the energy consumption of the five segments was increased.At the same time,the four segments of desalination decreased by 31.6 percent compared to compared with the one segment.3.Optimization of electrodialysis ion exchange membrane.The experiments explore the influence mechanism of different ion exchange membrane on electrodialysis desalination process,establish a basis for select ion exchange membrane,through the experiment obtain the conclusions as following: DE shan cao da ion exchange membrane of Japan desalination performance is optimal;The crosslinking degree of ionexchange membrane is the most important index to affect ion exchange membrane and electrodialysis performance.The four coefficients of electrodialysis process,the electric migration coefficient of ions ?,the diffusion coefficient of concentration difference of ions ?,the electric migration coefficient of water ?,the diffusion coefficient of concentration difference of the water ?.We hope to increase the electric migration coefficient of ions ?,reduce the he diffusion coefficient of concentration difference of ions ?,the electric migration coefficient of water ?,the diffusion coefficient of concentration difference of the water ?.Among them the electric migration coefficient of ions ? and the electric migration coefficient of water ? in the highest flight.The four correlation coefficients of electrodialysis process can be used as the main basis for selecting ion exchange membrane.