Zero brine, zero rinse water process for treatment of contaminated drinking water for removal of arsenic

Abstract

An ion exchange process for removing arsenic from drinking water is disclosed which uses a mixed ion regenerant and generates minimal levels of waste.

1 . A process for removing arsenic contamination from an arsenic-contaminated drinking water source additionally comprising feed water levels of at least one noncontaminant ion selected from the group consisting of chloride, sulfate and bicarbonate said process comprising 
 a. passing the arsenic-contaminated drinking water over a bed of ion exchange resin under conditions whereby the resin selectively absorbs arsenic contamination fro the drinking water thereby forming an arsenic-reduced drinking water product and a bed of arsenic-loaded ion exchange resin,    b. halting the passing of drinking water over the bed of arsenic-loaded ion exchange resin,    c. passing a regenerant solution over the bed of arsenic-loaded ion exchange resin, said regenerant solution comprising concentrated levels of said at least one noncontaminant ion said concentrated levels being related to one another as the feed water levels are related to one another, thereby displacing arsenic off of the ion exchange resin and forming a bed of regenerated ion exchange resin, the ions present on the regenerated resin being related to the feed water noncontaminant ion levels, and a spent regenerant solution, said spent regenerant solution containing an elevated level of arsenic,    d. separating the spent regenerant solution from said regenerated ion exchange resin,    e. treating the separated spent regenerant solution to selectively convert arsenic into an isolable form and to form a refreshed regenerant solution containing a reduced level of arsenic and concentrated levels of said at least one noncontaminant ion,    f. isolating the isolable arsenic and    g. recycling the refreshed regenerant solution to step c    
     
     
         2 . The process of  claim 1  wherein the regenerant solution contains at least two noncontaminant ions selected from chloride, sulfate and bicarbonate ions.  
     
     
         3 . The process of  claim 2  wherein the regenerant solution contains concentrated levels of said at least two noncontaminant ions said concentrated levels being related to one another as the feed water levelsof these ions are related to one another,  
     
     
         4 . The process of  claim 1  wherein the isolable form is a precipitate.  
     
     
         5 . The process of  claim 4  wherein the precipitate is a gel.  
     
     
         6 . The process of  claim 4  wherein the precipitate is an iron hydroxide/isolable arsenic coprecipitate.  
     
     
         7 . The process of  claim 1  wherein the flow of regenerant solution is carried out countercurrent to the direction of flow of contaminated drinking after over the bed.  
     
     
         8 . The process of  claim 1  additionally comprising the step of: 
 h. rinsing the regenerated ion exchange resin with water to provide a rinse water    
     
     
         9 . The process of  claim 8  additionally comprises the step of: 
 i. recovering the rinse water and removing water from it and returning the regenerant solution salts present in the recovered rinse water to the regenerant solution.    
     
     
         10 . The process of  claim 1  additionally comprising the step of steam stripping solids out of the regenerated resin.