Membrane Desalination Of Brackish Water With High Salt Content

Freshwater resources are vital to the development of a region or a country.With development of the world economy and population growth,the crisis of freshwater resources is becoming increasingly serious.Brackish desalination is particularly important to solve the crisis,especially for the arid areas in northwest China,exploring and developing new technologies from available water sources is the key to solve the freshwater resources crisis.Nowsdays,the water desalination of brackish generally adopts a single nanofiltration and reverse osmosis process,and there are few systematic studies on the mixed nanofiltration and reverse osmosis process.In particular,the study of desalination performance under the condition of real high salinity surface feed solution is more demonstrative significance for brackish desalination.In this thesis,a set of efficient and economical brackish water desalination equipment is designed to solve freshwater resources problems in the arid areas of northwest China.The real surface water was adopted as the feed in this work,firstly,the performance of microflocculation-precision filtration-ultrafiltration system as a pretreatment was evaluated.Secondly,the permeability and retention performance of nanofiltration and reverse osmosis with different number and combination of membrane elements were studied under the condition of operating pressure changes.On this basis,various assembly processes were compared;The performance of the desalination system was investigated by long-term operation experiments of the desalination system,In addition,the performance of the desalination system was evaluated when the feed solution with high salt content above 10 g/L,and finally the operating cost of the system was estimated.The results showed that the pretreatment process of microflocculation-precision filtration-ultrafiltration can meet the requirements of feed solution of the desalination system,and the hybrid nanofiltration and reverse osmosis system is superior to single nanofiltration and reverse osmosis system.The hybrid type of reverse osmosis in the front is more economical and efficient than nanofiltration in the front.The long-term operation experiment showed that the recovery rate of the desalination system could be maintained above 60%under the operating pressure of 1.3 MPa,the premeat water meet the drinking water standard;the operation cost of the whole small scale desalination equipment was 29.95 yuan·m^-3,and the daily water output could meet the water supply demand of small villages,which could be used to solve the problem of small-scale population in arid areas of Northwest China water shortage.