The present invention relates to a process for the selective removal of nitrates from ground water using a hybrid nanofiltration (NF)reverse osmosis (RO) filtration system. The process generates product water that is low in nitrate and can be used for drinking, irrigation and other purposes, as well as waste water that is relatively low in salinity and can be safely discarded to sewage systems and recycled, e.g., for irrigation purposes.

The invention concerns a subsea water processing system comprising an electrochemical unit that uses raw or treated seawater to generate high pH and low pH solutions that are used to clean at least one subsea process apparatus during a cleaning cycle by circulation through the at least one subsea process apparatus via acid or base flow lines connecting the electrochemical unit with the subsea process apparatus on-site.

A process for the coupled production of sweet whey and lactic acid from acid whey is suggested, comprising the following steps: (a) providing acid whey having a lactic acid content of about 0.1 to about 1% by weight; (b) nanofiltration of the acid whey, obtaining a first permeate P1 and a first retentate R1; (c) optionally, redilution of the first retentate R1 with water to reconstitute the initial dry matter content, and preparation of the second nanofiltration step; (d) nanofiltration or nano-diafiltration of the retentate R1, obtaining a second permeate P2 and sweet whey as a second retentate R2; (e) combining the two permeates P1 and P2 and subjecting the mixture to reverse osmosis, obtaining a third permeate P3 which, substantially, only contains water, and a concentrate of lactic acid as a third retentate R3.

The present invention relates to a method of concentrating an aqueous solution by low pressure under a zero osmotic pressure difference condition, and more particularly to a method of concentrating a solute-containing aqueous solution by low pressure under a zero osmotic pressure difference condition. When the method of the present invention is used, there are advantages in that energy consumption is low, and an aqueous solution can be concentrated until it can reach the maximum solute concentration or a solute concentration of 100%, without having to use an extraction solvent. In addition, there is an advantage in that the need to use a separate osmotic pressure draw solution is eliminated.

The present application includes a symbiotic reverse osmosis train system for maximizing desalinated water recovery, meanwhile yielding high salinity brine suitable for osmotic power generation or commercial salt production. The trains comprise a series of cells operating in an interrelated sequential pattern within a salinity field. Each cell forms a closed hydraulic brine loop having pumping means, power recovery means and shared semipermeable membranes between adjacent cells. Used are a semipermeable Flat Sheet or Hollow Fiber Membrane in desalination and osmotic power generation of brackish, seawater and brines of 15% salinity or more. Charging each cell in the train of cells with a formulated brine having a specified ionizable inorganic salt concentration and type, without permitting mixing of the given brines among adjacent cells. Allowing the train to achieve water recovery exceeding 85% with concentrated rejected brine of 28-30% salt content.

Concentration control in filtration systems and associated methods are generally described. Streams originating from upstream filters and having similar concentrations of a target minor component and/or similar osmotic pressures can be mixed and subsequently filtered within additional filters. Certain embodiments comprise recycling an output stream produced by a filter to a filter feed stream, wherein the output stream and the filter feed stream have similar concentrations of a target minor component and/or similar osmotic pressures. Such strategic mixing and/or recycling can reduce the amount of energy and/or the amount of filtration medium surface area required to achieve a desired concentration of the target minor component in a final product stream.

A method for concentrating and crystallizing fermentable carboxylic acids, salts, and mixtures thereof may involve the use of carboxylic acids that have a defined temperature dependence of the solubility and of the osmotic pressure. The carboxylic acids may be concentrated by a membrane method and subsequently crystallized out by a cooling crystallization and isolated. In some examples, the membrane method may involve nanofiltration, reverse osmosis, and/or membrane distillation for separation into a concentrate and a permeate. Similarly, an apparatus for implementing such methods may include a nanofiltration, reverse osmosis, and/or membrane distillation unit for concentrating the carboxylic acid, and at least one cooling crystallization unit for crystallizing the carboxylic acid.

The method of solvent recovery includes using a plurality of solvent recovery units to recover solvent from a dilute solution. The solvent recovery units can include a plurality of reverse osmosis or forward osmosis membrane systems arranged in series. For reverse osmosis, at least some of the concentrate in a last reverse osmosis unit of the series is recycled back to the permeate of that unit to provide a mixed permeate. The mixed permeate is then passed successively to the permeate side of each preceding reverse osmosis unit in the series. For forward osmosis, a draw solution is passed sequentially from the permeate side of each unit to the permeate side of the preceding unit. The draw solution may be prepared by concentrating part of the concentrate stream by evaporation and recycling it back as a draw solution.

A double-pass reverse osmosis (RO) separator module having two stages of RO filtration in a single assembly, including a radially outer RO assembly that surrounds a radially inner RO assembly, wherein each RO assembly includes an RO separation medium. The outer RO assembly may be used for a first-pass of RO filtration in which a first-pass feed liquid enters the outer RO assembly and is separated via reverse-osmosis to provide a permeate liquid and a concentrate liquid. The permeate liquid exiting the outer RO assembly may flow via fluid passages to the inner RO assembly for a second-pass of RO filtration in which the first-pass permeate liquid enters the inner RO assembly as a second-pass feed liquid and is separated via reverse-osmosis to provide a second-pass (i.e., double-filtered) permeate liquid.

A system for descaling apparatus is described. The system provides for: a water inlet feedstream; a reverse osmosis system in fluid communication with the water inlet feedstream, in which the reverse osmosis system produces a water permeate output feedstream; and a pressurised carbon dioxide feedstream. The pressurised carbon dioxide feedstream and water permeate output feedstream are arranged in use to combine to produce a pressurised carbonic acid input feedstream.