Reactive filtration

Abstract

In one embodiment, a reactive filtration method includes continuously regenerating a reactive filter media while simultaneously filtering contaminants from fluid flowing through the filter media. In one embodiment, regenerating the reactive filter media comprises mixing metal granules with the filter media and agitating the mixture. In another embodiment, regenerating the reactive filter media comprises introducing a metal in the fluid flowing through the filter media and agitating the filter media. In one embodiment, a method for removing phosphorus, arsenic or a heavy metal from water includes introducing a metal salt reagent into the water at a molar ratio of 5:1 to 200:1 to the phosphorous or the arsenic in the water and passing the water through a bed of moving sand.

What is claimed is: 
     
       1. A method, comprising:
 adding a metal salt reagent to water in sufficient quantity and concentration to allow precipitation reactions between the metal salt reagent and a dissolved contaminant in the water to go to at least near completion and to leave unreacted metal salt reagent in the water; 
 flowing the water through a serpentine pipe configured to produce more turbulent flow through bends in the pipe and less turbulent flow through straight-aways in the pipeinducing turbulence in the water; and then 
 flowing the water through a bed of moving filter media, wherein unreacted metal salt reagent in the water reacts with the filter media to generate a reactive metal oxide or hydroxide coating on the filter media to adsorb dissolved contaminants remaining in the water. 
 
     
     
       2. The method of  claim 1 , wherein inducing turbulence in the water comprises flowing the water through a serpentine pipe configured to produce more turbulent flow through bends in the pipe and less turbulent flow through straight-aways in the pipe, wherein the flowing the water through the serpentine pipe comprises maintaining water maintains sufficient flow in the serpentine pipe to inhibit deposition of solids, precipitates or particulates in the serpentine pipe. 
     
     
       3. The method of  claim 1 , wherein the contaminant is phosphorus, arsenic, selenium or another heavy metal and the metal salt reagent is ferric chloride, ferrous chloride, ferric sulfate or ferrous sulfate and the filter media is sand. 
     
     
       4. The method of  claim 2 , wherein the contaminant is phosphorous and unreacted ferric chloride, ferrous chloride, ferric sulfate or ferrous sulfate in the water entering the bed of moving sand provides a molar ratio of iron to phosphorus of 5:1 to 40:1. 
     
     
       5. The method of  claim 2 , wherein the contaminant is arsenic and unreacted ferric chloride, ferrous chloride, ferric sulfate or ferrous sulfate in the water entering the bed of moving sand provides a molar ratio of iron to arsenic of 100:1 to 200:1. 
     
     
       6. The method of  claim 2 , wherein the contaminant is arsenic and further comprising, before adding the metal salt reagent, oxidizing the water to convert arsenite in the water to arsenate. 
     
     
       7. A method comprising continuously regenerating a filter media by abrading the filter media sufficient to allow surface sites on the filter media to be available for reacting with a chemical reagent, while simultaneously filtering contaminants from fluid flowing through the filter media and continuously adding the chemical reagent to the fluid supplied to the filter media for reaction with the surface sites. 
     
     
       8. The method of claim  6  7, wherein the abrading scours the chemical reagent and compounds containing the chemical reagent and the contaminants from the filter media. 
     
     
       9. A method comprising:
 introducing iron oxides into water supplied to a moving bed media filter effective to precipitate contaminants from the water and to form iron oxide coated media surfaces in the moving bed media filter; 
 simultaneously filtering the precipitated contaminants with the moving bed media filter and sorbing other contaminants to the iron oxide coated media surfaces; 
 abrading sorbed contaminant-iron solids from the iron oxide coated media surfaces; 
 separating the precipitated and sorbed contaminants from the iron oxide coated media surfaces; and, 
 continuously introducing additional iron oxides to the moving bed media filter sufficient to regenerate the iron oxide coated media surfaces. 
 
     
     
       10. The method of  claim 9 , wherein the introducing iron oxides into water comprises introducing iron salts into the water in sufficient quantities to react with available water chemistries to form the iron oxides in quantities effective to precipitate a majority of the contaminants and to form the iron oxide coated media surfaces without significantly increasing iron concentrations of effluent water obtained from the moving bed media filter.