Abstract: Numerous water filtration systems are disclosed. Each filtration system contains one or more filtration units, and each filtration unit contains one or more membrane units. Each membrane unit receives impure water at high-pressure and filters the water with one or more reverse-osmosis membranes, yielding clean water. Leftover brine is discarded or mixed back into the input with the impure water. Each filtration system further comprises a control unit for controlling a feed valve, brine valve, and product valve for each membrane unit. Optionally, the control unit can sequence those activities to achieve constant energy consumption, minimal energy consumption, or constant output of clean water.

Abstract: Methods and systems for reducing contaminants and dissolved solids in wastewater produced by hydraulic fracturing operations using multiple reverse osmosis membrane stages.

Abstract: Methods and systems are disclosed for desalinating saltwater. The method includes (a) drawing feed water from a body of saltwater at a given depth below the surface of the body of saltwater; (b) transporting the feed water to one or more reverse osmosis vessels submerged in the body of saltwater and located a depth greater than the given depth at which the feed water is drawn in step (a); (c) controllably desalinating the feed water in the one or more reverse osmosis vessels to produce freshwater and brine concentrate such that the salinity of the brine concentrate is substantially the same as the salinity of the saltwater in the body of saltwater at a predetermined depth below the surface of the body of saltwater; and (d) discharging the brine concentrate into the body of saltwater at the predetermined depth below the surface of the body of saltwater.