Treatment Of High-Salinity Wastewater By Electrodialysis-Biological Method

Treatment of high-salinity organic wastewater is one of the difficulties andhotpots of today’s scholars at home and abroad. Biological and physical-chemicaltechniques have their own advantages and shortcomings in dealing with high-salinitywastewater, and the major need for research in the future will be the effectivecombination of physical-chemical and biological method. Conventional biochemicalmethod is the most widely used wastewater treatment technology. The salinity of thewastewater should be reduced before treatment by conventional biochemicaltreatment.The treatment of high-salinity wastewater by the electrodialysis-activatedsludge process was introduced in this study, intended to provide a new method forthe effective treatment of high-salinity wastewater. Driven by the forces of potentialdifference and concentration gradient, the salts of the high-salinity wastewatermigrated to the low-salinity draw solution in an electrodialyzer. After desalinationby electrodialysis, the wastewater was treated by activated sludge process to achievethe goal of high-salinity wastewater treatment.The electrodialyzer was fed with high saline and draw solution respectively,and the desalination performance of this electrodialysis system was studiedthroughly. The influence of various operating conditions, including influentconcentration, applied voltage, flow rate and rinse solution concentration on thedesalination performance of this system were evaluated. It was found that increasingapplied voltage, influent concentration and rinse solution concentration improveddesalination performance; however, the mass transport flux and operating currentdecreased with increasing flow rate. The orthogonal experiments were employed toevaluate effect of the above factors on mass transfer flux and operating current. Theresults showed that operating voltage was the most influential factor on desalinationperformance, and the concentration of rinse solution had the minimal impact. Theremoval performance of different ions by this electrodialysis system wasinvestigated. Under the same initial concentration and applied voltage, themembrane transported ions in the following order: K+>Na+>Mg2+, Cl->HCO3->SO42-.Moreover, simulate high-salinity wastewater was treated by desalination and biochemical process. The total salinity of the wastewater decreased from21380mg/Lto1583mg/L after treatment by electrodialysis for160min and the draw solutionchanged for5times. The results showed that the removal rate of bicarbonate ionswas less than70%, and the other ions displayed the rates higher than90%. Theconcentration of the organic matter has no obvious variation during the wholedesalination process. The desalinated wastewater was treated by activated sludgeprocess. Domestication of the sludge was conducted by gradually increasing theconcentration of COD in wastewater. The result of COD degradation was good after14days of domestication, and CODCrremoval efficiency was around85%after24hours treatment.