Removal Of Nitrate From Groundwater Using Cooperation Of Electrokinetic Remediation And Permeable Reaction Barrier

Groundwater is the important and even the only source of drinking water for lots ofpeople. However, whether in the developed or developing countries, nitrateconcentration of the groundwater increased and has become an environmental issuedue to the great application of nitrogen fertilizers and other reasons.Compared with the traditional groundwater pollution treatment technologies,Electrokinetic Remediation (EKR) and Permeable reactive barrier (PRB) technologyis able to realize continuously in-situ treatment and with the advantage of relativelyinexpensive; also could reduce the surface treatment facilities, reduce exposure andpollutants disturbance to the environment. However, both EKR and PRB used fornitrate removal showed that PRB filled with Fe0as media during the removal ofnitrate would produce more toxic NH4+, and EKE governance cycle is very long,often takes months or even longer.In order to achieve in-situ treatment, this study combined the respective advantagesof EKR and PRB technology to study the establishment of groundwater nitratepollution control technology for in situ EKR+PRB. According to taking advantages ofhigh adsorbed efficiency of PRB to NO3-, and EKR accelerate the migration of NO3-on PRB in order to realize efficient and harmless nitrate treatment.As the fundamental research of cooperation of EKR and PRB, Electrodialysis (ED)was studied first. The feasibility and removal of nitrate pollution from water werestudied from V-I curves, the effect of voltage, and the effect of water flow. Secondly,ED was combined with ion exchange resins. A special device named EKR+PRBintegrated small scale apparus was designed. Using this device, the effects of voltageon concentration of nitrate, pH, current efficiency and energy comsuption wasresearched and also the periodicity of “Adsorb-Electro regenerate-Adsorb” intermittent process. Thirdly, according to the EKR+PRB integrated small scaleapparus, a new and promoted device named EKR+PRB integrated middle scaleapparus was designed. And the periodicity of treatment process and the economicanalysis was studied.The results of ED showed that NO3--N concentration was reduced from initial50-300mg/L to1~6mg/L, with the removal rate99%and the conductivity could bereduced to less than10μs/cm. Under the conditions of equal (1,2,3,4,5,6,7,8L/h)and unequal (1:1,2,3,4,5,6,7,8L/h) water flow between concentrated and dilutedwater, the concentrated water could reach2-5times of the initial water. The currentefficiency and energy consumption was17~34%and0.1~1.7W·h/L, respectively. Itwas shown that ED was an effective treatment for NO3-removal and concentration.According to the small scale experiments,60V was the optimal voltage for electo-regenerating resins. And the period of “Adsorb-Electro regenerate-Adsorb”intermittent process was70h for adsorbing and70h for electro regenerating. Themaximum of electro-regeneration was35%. It’s effective to removal nitrate using theintermittent “Adsorb-Electro regenerate-Adsorb” process with low energy comsuptionand no second pollution.The promoted middle scale experiments showed that the period of “Adsorb-Electroregenerate-Adsorb” intermittent process was45h for adsorbing and90h for electroregenerating.2610L diluted water and1240L concentrated water could be obtainedfor every period; the content of concentrated water was100~170mg/L, and the dilutedwater could be decreased to2mg/L after a short increase (still below20mg/L) with95%removal rate. The maximum of electro-regeneration was23%. And nitratepollution of groundwater could be removed using the promoted EKR+PRB integratedapparus in-site.