An apparatus and process for separating a gas mixture is disclosed. The apparatus includes a first membrane stage, a second membrane stage, and a third membrane stage. The first membrane stage includes a first gas separation membrane configured to separate the gas mixture into a first retentate stream and a first permeate stream. The second membrane stage includes a second gas separation membrane configured to separate the first permeate stream into a second retentate stream and a second permeate stream. The second retentate stream of the second membrane stage is recycled back to connect with the first retentate stream to form a mixed fluid stream. The third membrane stage includes a third gas separation membrane configured to separate the mixed fluid stream into a third retentate stream and a third permeate stream, and the third retentate stream is configured to be withdrawn as a product or discarded.

Systems and methods for filtering materials from biologic fluids are discussed. Embodiments may be used to filter cerebrospinal fluid (CSF) from a human or animal subject. In an example, CSF is separated into a permeate and retentate using a tangential flow filter. The retentate is filtered again and then returned to the subject with the permeate. During operation of the system, various parameters may be modified, such as flow rate and waste rate.

A method for fractionating a sulfuric acid process stream having at least 1 wt % sulfuric acid, using a treatment system comprising three filtration assemblies each having membranes that are suitable to pass less than 10% salt in a standard test such that average passage of sulfuric acid from the first and third filtration assemblies is less than 30% and average passage of sulfuric acid from second filtration assembly is more than 70%. The system produces a fraction of the stream with a pH between 4 and 10, and a second fraction that contains at least 20 weight percent of sulfuric acid.

A desalination apparatus 12 (liquid treatment apparatus) includes a first water treatment unit 26 (liquid treatment unit) that includes a reverse osmosis membrane and in which a treated liquid is separated into a permeate that permeates the reverse osmosis membrane and a concentrate other than the permeate, a water recovery unit 28 (liquid recovery unit) that includes a reverse osmosis membrane and in which the concentrate is separated into a recovered liquid that permeates the reverse osmosis membrane and a waste liquid other than the recovered liquid, and a pressure increasing means that increases a liquid pressure of the concentrate, such that a state capable of separating into the recovered liquid and the waste liquid in the liquid recovery unit continues, and that directly feeds the concentrate from the liquid treatment unit to the liquid recovery unit.

Liquid solution concentration systems, and related methods, are generally described. In some embodiments, the system is an osmotic system comprising a plurality of osmotic modules. For example, the osmotic system can comprise a feed osmotic module configured to produce an osmotic module retentate outlet stream having a higher concentration of solute than the retentate inlet stream transported to the feed osmotic module. The osmotic system can also comprise an isolation osmotic module fluidically connected to the feed osmotic module. The osmotic system can also optionally comprise a purification osmotic module fluidically connected to the feed osmotic module and/or the isolation osmotic module. Certain embodiments are related to altering the degree to which the feed osmotic module retentate outlet stream is recycled back to the retentate-side inlet of the feed osmotic module during operation. Additional embodiments are related to the manner in which the retentate-side effluent from the isolation osmotic module is distributed among the system modules during operation.

The high water recovery hybrid membrane system for desalination and brine concentration combines nanofiltration, reverse osmosis and forward osmosis to produce pure water from seawater. The reject side of a nanofiltration unit receives a stream of seawater and outputs a brine stream. A permeate side of the nanofiltration unit outputs a permeate stream. A feed side of a reverse osmosis desalination unit receives a first portion of the permeate stream and outputs a reject stream. A permeate side of the reverse osmosis desalination unit outputs pure water. A draw side of at least one forward osmosis desalination unit receives the reject stream and outputs concentrated saline solution. A feed side of the at least one forward osmosis desalination unit receives a second portion of the permeate stream and outputs a dilute saline stream, which mixes with the first portion of the permeate stream fed to the reverse osmosis desalination unit.

Provided are electrodialysis systems comprising a plurality of electrodialysis devices, wherein each electrodialysis device of the plurality of electrodialysis devices has a product inlet stream, a product outlet stream, a brine inlet stream, and a brine outlet stream. The product inlet stream for a first electrodialysis device comprises the brine outlet stream of a second electrodialysis device. Further, a first portion of a feed stream is the brine inlet stream for the first electrodialysis device and a second portion of the feed stream is the brine inlet stream for the second electrodialysis device or a third electrodialysis device.

An apparatus and process for separating a gas mixture is disclosed. The apparatus includes a plurality of membrane separation stages comprising a first membrane stage, a second membrane stage, and a third membrane stage. Each of the first, second, and third membrane stages are designed to separate a gas stream provided to them into a permeate stream and a retentate stream. The retentate stream provided from the third membrane stage is configured to be withdrawn as a product, further processed, or discarded. The apparatus further includes a gas transport device with an inlet in communication with the gas mixture and an outlet in communication with the first membrane stage. The controller is in communication with at least one measuring device, and the controller adapts a behavior of the gas transport device in response to a measurement of the at least one measuring device.

A biogas upgrading system can include a multiple stage membrane system that is configured to remove oxygen so that the biogas is upgraded to have a higher concentration of methane, a pre-selected oxygen (O.sub.2) concentration (e.g. less than or equal to 0.2 mol %, etc.), and a pre-selected carbon dioxide (CO.sub.2) concentration (e.g. less than or equal to 5 mol %, etc.). The membrane system can be configured to reject O.sub.2 by utilizing a low CO.sub.2/O.sub.2 selectivity that is within a pre-determined range (e.g. less than 5 or less than 4.5). In some embodiments, the upgraded biogas that is output from the system can be entirely made up of methane, carbon dioxide, and oxygen. In other embodiments, the biogas can be almost entirely composed of these components along with a small amount of nitrogen and a trace amount (e.g. less than or equal to 0.2%-0.1%, etc.) of other components.

The present invention relates to a device and to a method for producing dialysate, wherein the device comprises a first part and a second part designed as a circuit, wherein the first part comprises a water connection or a water container and the primary side of a filter, wherein the filter is designed to produce purified water from the water by forward osmosis, and wherein the second part comprises the secondary side of the filter, a reservoir, a filtrate line which leads from the secondary side of the filter to the reservoir, and a return line leading from the reservoir to the secondary side of the filter, wherein an electrodialysis unit comprising a diluate chamber and a concentrate chamber is further provided, wherein the concentrate chamber is fluidically connected to the secondary side of the filter.