Process for purification of produced water

1. A process for purification of water, comprising:

collecting produced water including an oil/water mixture from an oil well;

separating and recovering oil from the produced water;

decreasing the pH of the produced water by addition of acid;

removing color, organics, and silica from the produced water;

adding a flocculent, including, optionally, a coagulant and a polyelectrolyte, to the produced water to aggregate solids in the produced water;

removing solids from the produced water, thereby producing a first sludge;

conditioning and disposing of the first sludge;

sending the produced water to an evaporator, producing a distillate stream and a brine stream;

sending the distillate stream to a boiler for evaporation into steam; and

sending a portion of the brine stream to a crystallizer for removal of additional distillate and production of a slurry to achieve zero liquid discharge without formation of a tarry mass.

2. The process of claim 1 , wherein the pH of the produced water is increased to between 9.5-10 after removal of color and organics and before sending the produced water to the evaporator.

3. The process of claim 1 , wherein between 60-80% of organics, 80-95% of color, and more than 25-50% of silica are removed from the produced water in the color removing step.

4. The process of claim 1 , wherein said brine stream is converted to a solid through absorption with super absorbent polymer.

5. The process of claim 1 , wherein said brine stream is neutralized to a pH between 8.5 and 9 with the addition of acid and without formation of a silica jelly.

6. The process of claim 1 , further comprising, after the step of conditioning and disposing of the first sludge, the steps of:

mixing the produced water with at least one of magnesium oxide and magnesium hydroxide; and

mixing the produced water with one or more of lime, calcium oxide, and sodium hydroxide, thereby precipitating silica from the produced water.

7. The process of claim 1 , further comprising, after precipitating silica from the produced water, removing the precipitated silica as a second sludge; and

conditioning and disposing of the second sludge.

8. The process of claim 7 , further comprising deaerating the produced water after at least one of separation of the first sludge and separation of the second sludge.

9. The process of claim 1 , wherein said acid addition lowers the pH of the produced water to between 3 to 5.

10. The process of claim 9 , wherein said acid addition lowers the pH of the produced water to between 4 to 4.5.

11. The process of claim 6 , wherein said mixing the produced water with one or more of lime, magnesium hydroxide, calcium oxide, and sodium hydroxide adjusts the pH to between 10-11.5.

12. A process for preconditioning water prior to treatment in an evaporation or reverse osmosis treatment, comprising:

providing a water stream including color;

removing color, organics, and silica from the water stream by the steps of:

adding an acid;

adding a color removal chemical; and

adding a flocculent to aggregate solids in the water stream;

removing the solids from the water stream;

increasing the pH of the water stream; and

sending the produced water to at least one of a evaporator and a reverse osmosis unit,

wherein a portion of the water leaving the at least one of the evaporator and the reverse osmosis unit is sent to a crystallizer for production of a slurry to achieve zero liquid discharge without formation of a tarry mass.

13. The process of claim 12 , wherein said produced water is sent to an evaporator.

14. The process of claim 12 , further comprising, prior to sending the water to a reverse osmosis unit, softening the water.

15. A process for preconditioning water prior to treatment in a reverse osmosis unit or evaporator, comprising:

providing water comprising silica, color, and organics;

decreasing the pH of the water by addition of acid;

removing color, organics, and silica from the water by addition of color-removal chemicals;

adding a flocculent to the water to aggregate solids in the water;

removing aggregated solids from the produced water, thereby producing a first sludge;

conditioning and disposing of the first sludge;

mixing the water with one or more of lime, magnesium oxide, calcium oxide, and sodium hydroxide, thereby precipitating additional solids;

removing the additional solids as a second sludge conditioning and disposing of the second sludge; and

sending the water to an evaporator or reverse osmosis unit,

wherein a portion of the water leaving the evaporator or the reverse osmosis unit is sent to a crystallizer for production of a slurry to achieve zero liquid discharge without formation of a tarry mass.

16. The process of claim 15 , wherein the water is sent to an evaporator.

17. The process of claim 15 , further comprising, prior to sending the water to a reverse osmosis unit, softening the water.

18. A process for purification of water, comprising:

collecting produced water including an oil/water mixture from an oil well;

separating and recovering oil from the produced water;

decreasing the pH of the produced water by addition of acid;

removing color, organics, and silica from the produced water;

adding a flocculent, including, optionally, a coagulant and a polyelectrolyte, to the produced water to aggregate solids in the produced water;

removing solids from the produced water, thereby producing a first sludge;

conditioning and disposing of the first sludge;

mixing the produced water with one or more of lime, magnesium oxide, magnesium hydroxide, calcium oxide, and sodium hydroxide, thereby precipitating silica from the produced water;

removing precipitated silica as a second sludge;

conditioning and disposing of the second sludge;

sending the produced water to an evaporator, producing a distillate stream and a brine stream;

sending the distillate stream to a boiler for evaporation into steam; and

sending a portion of the brine stream to a crystallizer for removal of additional distillate and production of a slurry to achieve zero liquid discharge without tar formation.

19. A two-stage process for silica reduction from water, comprising:

from a water stream comprising silica, water, and organics, coprecipitating at least some silica with color and organics;

precipitating additional silica from the water stream by addition of at least one silica-precipitating compound selected from the group consisting of lime, magnesium oxide, magnesium hydroxide, calcium oxide, and sodium hydroxide upstream of an evaporator or reverse osmosis system,

wherein a portion of the water leaving the evaporator or the reverse osmosis system is sent to a crystallizer for production of a slurry to achieve zero liquid discharge without formation of a tarry mass.

20. The process of claim 19 , wherein coprecipitation of silica with color and organics reduces the amount of silica-precipitating and overall process chemicals necessary to reduce silica to a desired level.