Treatment of iron contaminated liquids with an activated iron solids (AIS) process

Abstract

The present invention is a method and system for treating iron-contaminated water (e.g., mine drainage) using an innovative treatment approach identified herein as the Activated Iron Solids (AIS) Process. The AIS process is capable of oxidizing and removing iron as iron oxides from iron-contaminated waters (such as, mining-related discharge, groundwater, surface water and industrial waste streams) producing a clean effluent. The AIS process is performed in a single or multiple tank system in which a catalytic surface chemistry process increases the iron removal 1000s times faster than would naturally occur and 100s of times faster than existing arts (e.g., aerobic pond passive treatment). In addition, the AIS process can utilize inexpensive alkaline material (such as, pulverized limestone) where initial mine drainage alkalinity (mg/L as CaCO 3 ) to ferrous iron (mg/L) ratio is less than approximately 1.7. Excess accumulated iron oxides are periodically removed from the systems using a waste activated iron solids (WAIS) system and is directed to an Iron Oxide Thickener where the iron oxides are further concentrated.

1 . A system for removing ferrous iron from a fluid comprising: 
 a. At least one first container for receiving iron-contaminated fluid wherein said first container has at least one means of ingress and egress of fluid;    b. A means of transporting iron-contaminated fluid into said first container;    c. A means of aerating and mixing iron-contaminated fluid within said first container;    d. A means of decanting substantially iron-free supernatant fluid from said first container without disturbing settled iron oxides; and    e. A means of controlling the volume and temporal duration of transporting fluids in and out of said first container, aerating and mixing a fluid within said first container, and maintaining a fluid in a quiescent state in said first container.    
   
   
       2 . A system according to  claim 1  having a plurality of first containers.  
   
   
       3 . A system according to  claim 2  further comprising a means for selectively directing the flow of a fluid to at least one of said first containers.  
   
   
       4 . A system of  claim 1 ,  2  or  3  further comprising a means for delivering alkaline-bearing material into said first container.  
   
   
       5 . A system of  claim 1 ,  2 , or  3  further comprising: 
 a. A means for conveying fluid from a first container into a second container;    b. A means of mixing fluids in said second container;    c. A means of removing iron oxides from said second container; and    d. A means of decanting a substantially iron-free supernatant fluid from said second container.    
   
   
       6 . A system of  claim 4  further comprising: 
 a. A means for conveying fluid from a first container into a second container;    b. A means of mixing fluids in said second container;    c. A means of removing iron oxides from said second container; and    d. A means of decanting a substantially iron-free supernatant fluid from said second container.    
   
   
       7 . A method of removing ferrous iron from a fluid comprising: 
 a. Filling at least one first container with an iron-containing fluid;    b. Aerating the fluid within a first container sufficiently to ensure ferrous iron oxidation;    c. Mixing fluid within the first container sufficiently to maintain a suspension of iron oxide solids necessary to catalyze ferrous iron oxidation;    d. Storing activated iron solids within a first container sufficiently to maintain high reactor iron oxide concentrations necessary to catalyze ferrous iron oxidation;    e. Decanting a substantially iron-free supernatant fluid from a first container; and    f. Removing excess iron oxides from a first container.    
   
   
       8 . A method according to  claim 7  wherein a plurality of first containers are filled with a fluid to be treated.  
   
   
       9 . A method according to  claim 8  further wherein fluid is selectively directed either simultaneously or sequentially into first containers for treatment.  
   
   
       10 . A method of  claim 7 ,  8  or  9  further comprising adding alkaline-bearing material into a first container in sufficient quantity to provide sufficient alkalinity to precipitate iron oxides in a fluid to be treated.  
   
   
       11 . A method of claims  7 ,  8 , or  9  further comprising: 
 a. Conveying fluid from a first container into a second container;    b. Mixing fluids in a second container;    c. Removing iron oxides from a second container; and    d. Decanting a substantially iron-free supernatant fluid from a second container.    
   
   
       12 . A method of  claim 10  further comprising: 
 a. Conveying fluid from a first container into a second container;    b. Mixing fluids in a second container;    c. Removing iron oxides from a second container    d. Decanting a substantially iron-free supernatant fluid from a second container.    
   
   
       13 . A method of  claim 7 ,  8  or  9  further comprising mixing fluids sufficiently to promote flocculation after said storing of activated iron solids within a first container sufficiently to maintain high reactor iron oxide concentrations necessary to catalyze ferrous iron oxidation.