Method and system for performing reverse osmosis with integrated pump storage

A method of operating a reverse osmosis system coupled to a reservoir a fluid source located below the reservoir, the system comprises a first pretreatment system, a first membrane housing comprising a first reverse osmosis membrane therein, the first membrane housing comprising a first feed fluid inlet, a first brine outlet and a first permeate outlet, a first turbocharger comprising a first pump portion and a first turbine portion, a second turbocharger comprising a second pump portion and a second turbine portion, a third turbocharger comprising a third pump portion and a third turbine portion, a second pretreatment system and a booster pump, said method comprising:

• communicating fluid to a fluid reservoir from the fluid source through a pump-turbine;
• communicating the fluid through the first pretreatment system to form feed fluid;
• pressurizing the feed fluid at the first pump portion;
• communicating the feed fluid to the first feed fluid inlet from the first pump portion;
• communicating brine fluid from the first brine outlet of first membrane housing to the first turbine portion to operate the first pump portion;
• communicating brine from the first turbine portion to the second turbine portion to operate the second pump portion and the third turbine portion to operate the third pump portion;
• communicating second feed fluid from the fluid source through the second pretreatment system to the second pump portion;
• increasing a pressure of the second feed fluid at the second pump portion;
• thereafter, communicating the second feed fluid to the third pump portion to increase the pressure of the second feed fluid;
• and
• communicating the second feed fluid from the third pump portion to the first pump portion.