A submersible water desalination apparatus includes an array of generally parallel water separation membrane cartridges each having a water separation membrane, an impermeable cartridge wall surrounding the membrane, and a product water collection tube that collects from inside the cartridges at least partially desalinated product water passing through the membrane, and through which the at least partially desalinated water exits the cartridges and enters a product water collection manifold. The cartridges are mounted in a perforated divider plate. In embodiments, a) the manifold is adhesively bonded to a plurality of the collection tubes, orb) the divider plate is adhesively bonded to a plurality of the cartridge walls or ends, or both a) and b). The adhesive reduces the likelihood of leakage at the manifold or divider plate.

A serial filtration system for liquid purification includes a preliminary-stage reverse-osmosis (RO) module and a first-stage, high-permeability, reverse-osmosis (HiRO) module. Both modules include (a) a chamber including an inlet, a retentate outlet, and a permeate outlet, and (b) at least one membrane separating the chamber into a retentate side on an upstream side of the membrane and a permeate side on a downstream side of the membrane. The membrane in the preliminary stage is an RO membrane, while the membrane in the first stage is an oxidized membrane. The first-stage inlet is in fluid communication with the preliminary-stage, retentate outlet; and the oxidized membrane in the first stage, comprises an oxidized polyamide active layer coated on a porous support, wherein the oxidized polyamide active layer has an atomic oxygen/nitrogen ratio of at least 1.5.

A submersible reverse osmosis desalination apparatus uses low temperature concentrate or brine from the desalination apparatus to provide a high volume cold liquid stream to an Ocean Thermal Energy Conversion (OTEC) heat engine. The OTEC engine also employs a warm liquid stream and uses the cold and warm liquid streams to obtain electrical power from a closed-cycle or open-cycle heat exchange and generator system. Use of the concentrate or brine stream provides a much greater liquid volume and much greater cold thermal energy content than would be obtained by using cold desalinated product water from the desalination apparatus in the OTEC heat engine.

A method of treating water in a water treatment system after a replacement of an ion exchange bed includes introducing water to be treated into the ion exchange bed of the water treatment system to produce treated water, calculating a current exchange daily average flow rate of water through the water treatment system, calculating a cumulative daily average flow rate of water through the water treatment system, and determining an estimated number of days remaining to exhaustion of the ion exchange bed based on the current exchange daily average flow rate and the cumulative daily average flow rate.

A submersible water desalination apparatus includes an array of hot-swappable water separation membrane modules arrayed in an approximately polygonal configuration around a product water collection conduit that represents or is proximate to and generally aligned with a central axis of the array; a plurality of hot-swap product water valves connected to the conduit and detachably connected to generally radially-extending product water collection manifolds in fluid communication with a plurality of water separation membrane cartridges within the modules; the modules having in cross-section generally tapered module sides that converge towards the conduit and assist in underwater docking and attachment of a replacement module to a hot-swap product water valve.

A submersible water desalination apparatus includes a plurality of water separation membrane elements that when supplied with salinated water under pressure at a first depth will produce at least partially desalinated product water and concentrate or brine; a product water collector that receives product water from the membrane elements; and a permeate conduit that transports product water from the collector downwardly to a motorized submersible pump remotely located from the membrane elements and collector at a second depth greater than the first depth. The second depth is sufficiently greater than the first depth so that the height of a standing column of product water in the product water collector and permeate conduit between the membrane elements and the suction side of the pump maintains a net positive suction head that prevents inlet side cavitation during pump startup and operation.

A filtration apparatus includes a tubular casing having a longitudinal axis and first and second casing ends, a plurality of partition plates positioned in the casing and sealed thereto to thereby define an intake collection chamber between a first of said partition plates and the first casing end, a discharge collection chamber between a second of said partition plates and the second casing end, and a reject collection chamber opposite the second partition plate from the second casing end, a plurality of elongated filtration membrane stacks positioned side-by-side in the casing generally parallel to the longitudinal axis, each filtration membrane stack comprising an intake end fluidly connected to the intake collection chamber, a discharge end fluidly connected to the reject collection chamber, and a permeate channel extending between the first and second ends and fluidly connected to the discharge collection chamber. The filtration apparatus also includes an intake pipe connected to the intake collection chamber, a discharge pipe connected to the discharge collection chamber, and a reject pipe connected to the reject collection chamber. Each filtration membrane stack is made of a plurality of filtration membranes which are each sealed to a corresponding hole in a corresponding partition plate, each filtration membrane having an inlet end and an outlet end and being sealed to the corresponding hole between the inlet and outlet ends, and the outlet end being spaced apart from an adjacent partition plate located closer to the second casing end.

A UV disinfection system including at least one UV lamp assembly with a sleeve surrounding a UV lamp and defining an inner volume. The UV disinfection system further includes at least one pressure sensor. At least one non-return valve connects the inner volume of the at least one sleeve to the pressure sensor. The UV disinfection system is configured to detect a sleeve breakage by the resulting change in pressure at the at least one pressure sensor. A break detection device for a UV disinfection system with a pressure detector includes at least one tubing which communicates directly or indirectly with an inner volume of a sleeve surrounding at least one of a UV lamp unit.

A submersible water desalination apparatus includes an array of generally parallel water separation membrane cartridges each having a water separation membrane, an impermeable cartridge wall surrounding the membrane, and a product water collection tube that collects from inside the cartridges at least partially desalinated product water passing through the membrane, and through which the at least partially desalinated water exits the cartridges and enters a product water collection manifold. The cartridges are mounted in a perforated divider plate. In embodiments, a) the manifold is adhesively bonded to a plurality of the collection tubes, orb) the divider plate is adhesively bonded to a plurality of the cartridge walls or ends, or both a) and b). The adhesive reduces the likelihood of leakage at the manifold or divider plate.

A submersible water desalination apparatus includes a plurality of water separation membrane elements, a product water collector that receives product water from the membrane elements, and a variable output motorized submersible pump having a suction side that receives product water from the product water collector and a discharge side that pumps product water away from the apparatus through a product water conduit for surface or subsurface use. An automatic control or coupling is employed to reduce the pump output upon the occurrence or onset of suction side cavitation, and discourage or prevent cavitation over a range of product water flow rates from the membrane elements.