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Methods and apparatus for demulsifying oil in water by dilution and impact, and for separation of the oil and suspended solids by dissolved gas floatation, are described. A produced water treating system is also described. The produced water treating system may include a dissolved gas floatation cla

Methods and apparatus for demulsifying oil in water by dilution and impact, and for separation of the oil and suspended solids by dissolved gas floatation, are described. A produced water treating system is also described. The produced water treating system may include a dissolved gas floatation clarifier system, an oil demulsification system, and a separation system. A demulsification subsystem is also described. The apparatus may include a liquid-liquid fluid mixer and a gas generator.

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1. A water treating system for treating produced water containing suspended solids and emulsified oil, the water treating system comprising:a dissolved gas floatation clarifier system to remove suspended solids and emulsified oil as sludge, the dissolved gas floatation clarifier system adapted to se

1. A water treating system for treating produced water containing suspended solids and emulsified oil, the water treating system comprising:a dissolved gas floatation clarifier system to remove suspended solids and emulsified oil as sludge, the dissolved gas floatation clarifier system adapted to separate the produced water into clarified water and sludge of suspended solids and emulsified oil, and an oil demulsification and separation system to demulsify and remove oil remaining in the clarified water from the dissolved gas floatation clarifier system, in which the dissolved gas floatation clarifier system comprises: a dissolved gas floatation clarifier having a manifold, a clarified water outlet, and a sludge collection chamber to collect sludge, the dissolved gas clarifier being enclosed; a storage tank for collecting clarified water exiting the outlet of the dissolved gas floatation clarifier; a pressurized gas supply in fluid communication with the dissolved gas floatation clarifier to supply pressurized gas to the dissolved gas clarifier; a recycle pressure aeration system adapted to pressurize the clarified water from the storage tank with a recycling pump; a dissolved gas generator adapted to dissolve gas from the dissolved gas clarifier into the pressurized clarified water from the recycle pressure aeration system to form a fluid saturated with dissolved gas to serve as emulsified oil diluent and to supply flotation bubbles to the dissolved gas flotation clarifier; a water pump adapted to pressurize the produced water; and a liquid-liquid fluid mixer adapted to mix the pressurized produced water from the water pump with the fluid saturated with dissolved gas exiting the dissolved gas generator to dilute the emulsified oil and form a mixture of demulsified oil and excess dissolved gas with water, the liquid-liquid fluid mixer providing the mixture to the manifold of the dissolved gas floatation clarifier, wherein the dissolved gas floatation clarifier separates the mixture from the liquid-liquid mixer into sludge and clarified water, the sludge being collected in the sludge collection chamber, the clarified water collected in the storage tank. 2. The water treating system of claim 1 in which a pressure of the gas in the enclosed dissolved gas floatation clarifier is maintained to a preset level by a pressure regulator.3. The water treating system of claim 1, in which the dissolved gas floatation clarifier further comprises:a retention chamber for receiving the mixture exiting the manifold, in which the dissolved gas comes out of solution to form gas bubbles, the gas bubbles attaching to float suspended solids and demulsified oil as contaminants; a floatation cell for allowing the contaminants to float above the water in the floatation cell; a rake assembly adapted to move the floating contaminants from the floatation cell into a sludge collection chamber; and a passageway having an outlet for clarified water to exit the dissolved gas floatation clarifier. 4. The water treating system of claim 3 in which the floatation cell has a settling zone, the floatation cell being conical with a lower end, contaminants in the settling zone settling in the lower end of the conical floatation cell.5. The water treating system of claim 4 further comprising a sludge pump to selectively remove contaminants as sludge from the sludge collection chamber through a sludge outlet.6. The water treating system of claim 5 in which the sludge pump selectively removes contaminants settled on the bottom of the floatation cell as sludge through a sludge outlet port.7. The water treating system of claim 4 in which the sludge container is separated from the floatation cell by an incline.8. The water treating system of claim 7 in which the retention chamber is separated from the floatation cell by a weir.9. The water treating system of claim 4 in which the rake assembly further comprises:a plurality of rakes; and a variable speed drive motor, the plurality of rakes adapted to rake the floating contaminants as sludge off the water in the floatation cell and into the sludge collection chamber. 10. The water treating system of claim 1 wherein the gas in the pressurized gas supply is either carbon dioxide or methane.11. The water treating system of claim 1, in which the dissolved gas generator further comprises:an upper cylindrical donut housing with a fluid inlet for the clarified water, the upper cylindrical donut housing having a gas separation chamber to separate excess gases from liquids for discharging gas through a gas outlet on the upper housing; a grooved ring having a plurality of grooves, an impact zone being located below the grooved ring, the grooved ring being concentric to the upper cylindrical donut housing, the grooved ring having an outer diameter on a first end that is smaller than a diameter of the upper cylindrical donut housing, thus defining a distribution channel; a venturi-orifice ring adapted to inject gas from the dissolved gas clarifier into liquid leaving the grooves; and a cylinder concentric with the grooved ring, the cylinder in fluid communication with the distribution channel via the grooves, a saturated liquid outlet being located a bottom of the cylinder, to form the fluid saturated with gas. 12. The water treating system of claim 1, in which the oil demulsification and separation system comprises:a demulsification subsystem having a first stage adapted to selectively mix clarified water from the dissolved gas floatation system at a pressure sufficient to allow flow into a low pressure tank; and a dissolved gas separation subsystem adapted to receive fluid from the demulsification system, and separate the oil and gas from water by floatation. 13. The water treating system of claim 1, in which the liquid mixer further comprises:an upper donut housing with a first fluid inlet in the upper housing; a ring having a plurality of grooves, the ring being concentric to the upper donut housing, the ring having an outer diameter on a first end that is smaller than a diameter of the donut housing thus defining a distribution channel; an orifice ring adapted to inject a second liquid into the first liquid leaving the grooves; and a cylinder concentric with the ring and surrounded by the ring, the cylinder in fluid communication with the distribution channel via the grooves, a liquid outlet being located at the bottom of the cylinder. 14. A water treating system for treating produced water containing suspended solids and emulsified oil, the water treating system comprising:a dissolved gas floatation clarifier system to remove suspended solids and emulsified oil as sludge, the dissolved gas floatation clarifier system adapted to separate the produced water into clarified water and sludge of suspended solids and emulsified oil, and an oil demulsification and separation system to demulsify and remove oil remaining in the clarified water from the dissolved gas floatation clarifier system, the oil demulsification and separation system having a first fluid mixer adapted to selectively mix clarified water from the dissolved gas floatation clarifier system with light petroleum to selectively produce a mixture of water and light petroleum diluent to mix with any trace demulsified oil; a low pressure tank adapted to store fluid and having a lower portion separated from an upper space by a layer of floating oil, the upper space adapted to collect gas; a dissolved gas generator adapted to mix water from the lower portion of the low pressure tank with gas from the upper space of the low pressure tank to produce saturated water; and a second fluid mixer adapted to mix the mixture of water and light petroleum diluent from the first fluid mixer with water saturated with dissolved gas exiting from the dissolved gas generator to dilute the emulsified oil and form a mixture of oil and excess dissolved gas with water, the oil-water-excess dissolved gas mixture distributed in the fluid of the low pressure tank via an upper distributor, wherein upon entering the low pressure tank from the upper distributor, the gas comes out of solution to separate oil by floatation, the oil floating above the water in the low pressure tank, the gas collected in the upper space of the low pressure tank above the floating oil, and the water exiting the lower portion of the low pressure tank via a bottom outlet port. 15. The water treating system of claim 14 further comprising:a second dissolved gas generator adapted to mix water pumped from the lower portion of the tank with gas from the upper space of the tank, the water saturated with gas exiting the second dissolved gas generator and entering the low pressure tank through a plurality of lower distributors, each plurality of lower distributors being located below the upper distributor in the low pressure tank. 16. The water treating system of claim 15, in which the second dissolved gas generator further comprises:a second upper cylindrical donut housing with a second fluid inlet for the water pumped from the lower portion of the low pressure tank, the second upper cylindrical donut housing having a second gas separation chamber to separate excess gases from liquids for discharging gas through a second gas outlet on the second upper housing; a second grooved ring having a plurality of grooves, a second impact zone being located below the second grooved ring, the second grooved ring being concentric to the second upper cylindrical donut housing, the second grooved ring having an outer diameter on a first end that is smaller than a diameter of the second upper cylindrical donut housing, thus defining a second distribution channel; a second venturi-orifice ring adapted to inject gas from the upper space of the tank into liquid leaving the grooves; and a second cylinder concentric with the second grooved ring, the second cylinder in fluid communication with the distribution channel via the grooves, a second saturated liquid outlet being located a bottom of the cylinder, to form the water saturated with gas. 17. The water treating system of claim 14, in which the liquid mixer further comprises:an upper donut housing with a first fluid inlet in the upper housing; a ring having a plurality of grooves, the ring being concentric to the upper donut housing, the ring having an outer diameter on a first end that is smaller than a diameter of the donut housing thus defining a distribution channel; an orifice ring adapted to inject a second liquid into the first liquid leaving the grooves; and a cylinder concentric with the ring and surrounded by the ring, the cylinder in fluid communication with the distribution channel via the grooves, a liquid outlet being located at the bottom of the cylinder. 18. The water treating system of claim 14 in which the floating oil is selectively removed via an oil outlet chamber, the oil outlet chamber adapted to maintain an oil head pressure on the gas collected in the upper space of the low pressure tank.19. The water treating system of claim 14 in which excess gas not mixed in the dissolved gas generator is returned to the upper space of the low pressure tank.20. The water treating system of claim 14 in which the gas is methane or carbon dioxide.21. The water treating system of claim 14 in which the clarified water from the dissolved gas clarifier floatation system enters the first mixer at a predetermined pressure controlled by a pressure regulator, wherein the predetermined pressure is a function of a head pressure at the upper distributor and an amount of emulsified oil in the clarified water exiting the dissolved gas clarifier system.22. The water treating system of claim 14 in which the light petroleum is provided by a light petroleum supply system, the light petroleum supply system further comprisinga light petroleum storage tank; a light petroleum feed pump; a light pump bypass; and a pressure regulator, wherein the light petroleum is pumped from the light petroleum storage tank through the petroleum feed pump, and into the first fluid mixer. 23. The water treating system of claim 14 in which the pressure within the low pressure tank is maintained at a value below six ounces per square inch.24. The water treating system of claim 14 in which the floating oil is selectively drawn out of the low pressure tank through an oil outlet chamber to maintain an oil head pressure.25. The water treating system of claim 14, in which the dissolved gas generator further comprises:an upper cylindrical donut housing with a fluid inlet for the water pumped from the lower portion of the low pressure tank, the upper cylindrical donut housing having a gas separation chamber to separate excess gases from liquids for discharging gas through a gas outlet on the upper housing; a grooved ring having a plurality of grooves, an impact zone being located below the grooved ring, the grooved ring being concentric to the upper cylindrical donut housing, the grooved ring having an outer diameter on a first end that is smaller than a diameter of the upper cylindrical donut housing, thus defining a distribution channel; a venturi-orifice ring adapted to inject gas from the from the upper space of the low pressure tank into liquid leaving the grooves; and a cylinder concentric with the grooved ring, the cylinder in fluid communication with the distribution channel via the grooves, a saturated liquid outlet being located a bottom of the cylinder, to form the saturated water. 26. The water treating system of claim 14 in which the outlet port is located substantially at a bottom of the low pressure tank, the water is pumped from the lower portion of the low pressure tank to the dissolved gas generator, and the saturated water from the dissolved gas generator also provides flotation bubbles to the low pressure tank.27. The water treating system of claim 14, in which the oil demulsification and separation system comprises:a demulsification subsystem having a first stage adapted to selectively mix clarified water from the dissolved gas floatation system at a pressure sufficient to allow flow into a low pressure tank; and a dissolved gas separation subsystem adapted to receive fluid from the demulsification system, and separate the oil and gas from water by floatation.