Methods and systems for reducing biofouling of microfiltration membranes

1. A method for reducing biofouling of microfiltration membranes by a biomolecule-based exopolymeric substance, the method comprising:

providing impound water comprising a biomolecule-based exopolymeric substance;

reacting the impound water with calcium oxide or calcium hydroxide to generate a calcium-treated biomolecule-based exopolymeric substance mixture;

encapsulating the reacted biomolecule-based exopolymeric substance into filterable, non-tacky particles by reacting the calcium-treated biomolecule-based exopolymeric substance mixture with an aluminum-based inorganic coagulant and a cationic polymer having a molecular weight in the range from about 200,000 to about 800,000 Daltons (Da) having a molecular weight in the range from 200,000 to 800,000 Da;

removing a first portion of the encapsulated biomolecule-based exopolymeric substance as bulk solid; and

removing a second portion of the encapsulated biomolecule-based exopolymeric substance by low pressure microfiltration through a microfiltration membrane comprising a pore size of between about 0.7 to 12 microns,

wherein encapsulating the biomolecule-based exopolymeric substance into filterable, non-tacky particles reduces biofouling of the microfiltration membrane.

2. The method of claim 1 , wherein the calcium oxide or calcium hydroxide is reacted at a final concentration of between about 100 mg/L to 225 mg/L.

3. The method of claim 1 , wherein the inorganic coagulant comprises aluminum chlorohydrate.

4. The method of claim 3 , wherein the aluminum chlorohydrate is reacted at a final concentration of about 25 mg/L to 75 mg/L.

5. The method of claim 1 , wherein the cationic polymer comprises epi-dma (poly(epichlorhydrin-dimethylamine).

6. The method of claim 1 , wherein the inorganic coagulant and cationic polymer are reacted with the calcium-treated biomolecule-based exopolymeric substance mixture at a ratio of coagulant to polymer of about 1:1 to 10:1.

7. The method of claim 1 , wherein the microfiltration membrane comprises polypropylene, polysulfone, polyethylene, polytetrafluoroethylene, or combinations thereof.

8. The method of claim 1 , wherein the microfiltration membrane comprises a pore size between about 1 to 2.5 microns.

9. The method of claim 1 , wherein microfiltering further comprises:

microfiltering with a microfilter membrane at a back pressure of less than about 15 pounds per square inch and at a flow rate of at least 650 gallons per square foot of microfilter membrane per day; and

periodically backwashing the microfilter membrane to remove collected filterable non-tacky particles.

10. A method for removing polysaccharide-based exopolymeric substance from an aqueous mixture, the method comprising:

providing an aqueous mixture, the aqueous mixture containing exopolymeric substance and one or more of dissolved solids, suspended solids or heavy metals;

reacting the aqueous mixture with calcium oxide or calcium hydroxide to generate a calcium-treated mixture;

encapsulating the reacted polysaccharide-based exopolymeric substance into filterable, non-tacky particles by reacting the calcium-treated mixture with aluminum chlorohydrate and epi-dma (poly(epichlorhydrin-dimethylamine);

mechanically removing a first portion of the encapsulated polysaccharide-based exopolymeric substance as bulk solid; and

microfiltering to remove a second portion of the encapsulated polysaccharide-based exopolymeric substance.

11. The method of claim 10 , wherein microfiltering further comprises:

microfiltering with a microfilter membrane at a back pressure of less than about 15 pounds per square inch and at a flow rate of at least 650 gallons per square foot of microfilter membrane per day; and

periodically backwashing the microfilter membrane to remove collected filterable non-tacky particles.

12. The method of claim 10 , further comprising microfiltering with a microfilter membrane comprising polypropylene, polysulfone, polyethylene, polytetrafluoroethylene, or combinations thereof.

13. The method of claim 11 , wherein the microfilter membrane comprises a pore size between about 0.7 and about 12 microns.

14. The method of claim 11 , wherein the microfilter membrane comprises a pore size between about 1 to 2.5 microns.