Reverse osmosis system with control based on flow rates in the permeate and brine streams

1. A method of operating a reverse osmosis system, wherein the reverse osmosis system comprises (i) a membrane chamber having a feed line and generating a permeate stream and a brine stream, and (ii) a booster device having a turbine portion in fluid communication with the brine stream, a pump portion in fluid communication with the feed line, and a first motor coupled to the turbine portion using a common shaft between the turbine portion, pump portion, and first motor, the method comprising:

pressurizing the feed line using a feed pump;

generating a first flow signal, via a first flow meter, corresponding to a flow of fluid in the permeate stream;

operating a variable frequency drive attached to the first motor in response to the first flow signal;

controlling the first motor in response to the variable frequency drive;

generating a second flow signal, via a second flow meter, corresponding to a flow of fluid in the brine stream; and

controlling an opening to the turbine portion by adjusting a variable size nozzle in response to the second flow signal.

2. A method as recited in claim 1 , wherein controlling the first motor comprises controlling the first motor to act as a generator when the first flow signal is above a control point to generate electrical power for the reverse osmosis system.

3. A method as recited in claim 1 , wherein controlling the opening comprises decreasing a size of the opening to decrease a brine flow rate.

4. A method as recited in claim 1 , wherein controlling the opening comprises increasing a size of the opening to increase a brine flow rate.

5. A method as recited in claim 1 , further comprising providing a first isolation valve disposed between the feed pump and the booster device.

6. A method as recited in claim 5 , further comprising providing a second isolation valve disposed between the booster device and a brine manifold.

7. A method as recited in claim 6 , further comprising providing a third isolation valve in fluid communication with the permeate stream.

8. A method as recited in claim 1 , wherein the first motor is an induction motor.

9. A method as recited in claim 1 , wherein the variable frequency drive is a regenerative variable frequency drive.

10. A method of operating a multi-stage reverse osmosis system having a feed manifold, a permeate manifold and a plurality of reverse osmosis stages fluidically coupled to the feed manifold and the permeate manifold, wherein each stage of the multi-stage reverse osmosis system comprises a membrane chamber having a feed line, wherein said membrane chamber generates a permeate stream and a brine stream, wherein each of the stages further comprises (i) a booster device having a turbine portion in fluid communication with the brine stream, a pump portion in fluid communication with the feed line, a variable frequency drive attached to a first motor, said turbine portion, pump portion and first motor comprising a common shaft, the method comprising:

pressurizing a feed stream within the feed manifold with a feed pump to form a pressurized feed stream;

at each of the stages:

passing the pressurized feed stream through the feed line;

generating a first flow signal, in a first flow meter, corresponding to a flow of fluid in the permeate stream;

operating the variable frequency drive of the first motor in response to the first flow signal;

controlling the first motor in response to the variable frequency drive;

generating a second flow signal, via a second flow meter, corresponding to a flow of fluid in the brine stream; and

controlling an opening to the turbine portion by adjusting a variable size nozzle in response to the second flow signal.

11. A method as recited in claim 10 , wherein controlling the first motor comprises controlling the first motor to act as a generator when the first flow signal is above a control point to generate power for a reverse osmosis power system from the generator.

12. A method as recited in claim 10 , wherein controlling an opening comprises controlling the opening smaller to decrease a brine flow rate.

13. A method as recited in claim 10 , wherein controlling an opening comprises controlling the opening larger to increase a brine flow rate.

14. A method as recited in claim 10 , further comprising providing a first isolation valve disposed between the feed pump and the booster device for each stage.

15. A method as recited in claim 14 , further comprising providing a second isolation valve disposed between the booster device and a brine manifold.

16. A method as recited in claim 15 , further comprising providing a third isolation valve in fluid communication with the permeate stream.

17. A method as recited in claim 10 , wherein operating the variable frequency drive comprises operating the variable frequency drive for an induction motor.

18. A method as recited in claim 10 , wherein operating the variable frequency drive comprises operating a regenerative variable frequency drive for the first motor.

19. A method as recited in claim 1 , further comprising:

driving a turbine via the first motor,

wherein

the turbine portion comprises the turbine,

the pressurizing of the feed line is performed via a first pump and includes a second motor driving the first pump, and

the pump portion comprises a second pump; and

driving the second pump via the turbine.

20. A method as recited in claim 1 , wherein:

the turbine portion comprises a turbine;

the controlling of the first motor comprises transitioning the first motor to operate as a generator when the first flow signal is above a control point to generate electrical power for the reverse osmosis system; and

the generator is driven by rotation of the turbine.

21. A method as recited in claim 1 , wherein:

the turbine portion comprises a turbine; and

the second flow signal indicates an amount of fluid flow provided from the brine stream to the turbine.