Abstract: Algae harvesting and cultivating systems and methods for producing high concentrations of algae product with minimal energy. In an embodiment, a dead-end filtration system and method includes at least one tank and a plurality hollow fiber membranes positioned in the at least one tank. An algae medium is pulled through the hollow fiber membranes such that a retentate and a permeate are produced.

Abstract: A micro alternating tangential flow (microATF) perfusion filter includes a hollow cylinder having a proximal end and a distal end. The proximal end is connected in series to a permeate chamber, followed by a retentate chamber. The proximal end either (i) terminates in or at the permeate chamber, or (ii) terminates in or at the retentate chamber. The portion of the proximal end within the permeate chamber, in a case of (ii), possesses at least one opening allowing fluid communication between an inside of the hollow cylinder and the permeate chamber. The microATF perfusion filter further includes an inlet, positioned over the retentate chamber, for communication with a source of positive or negative pressure, and an outlet, positioned in a wall of the permeate chamber, which can be connected to a check valve, which, in turn, can be connected to a hydrophobic fluid vent filter.

Abstract: The present disclosure relates generally to systems and methods for recycling lead-acid batteries, and more specifically, relates to purifying and recycling the lead content from lead-acid batteries. A system includes a reactor that receives and mixes a lead-bearing material waste, a carboxylate source, and a recycled liquid component to form a leaching mixture yielding a lead carboxylate precipitate. The system also includes a phase separation device coupled to the reactor, wherein the phase separation device isolates the lead carboxylate precipitate from a liquid component of the leaching mixture. The system further includes a closed-loop liquid recycling system coupled to the phase separation device and to the reactor, wherein the closed-loop liquid recycling system receives the liquid component isolated by the phase separation device and recycles a substantial portion of the received liquid component back to the reactor as the recycled liquid component.

Abstract: A sensor system, particularly for monitoring the mixing of at least two fluids and a method for monitoring the mixture of at least two liquids. The present invention provides a sensor system for fluids, comprising at least two level sensor which are arranged vertically one upon the other on and connected to an electronic circuit board, four electrodes of four conductivity sensors which are arranged horizontally next to each other at the bottom of and connected to the electronic circuit board; and a temperature sensor which is connected to the electronic circuit board; a connector for connecting the electronic circuit board to a controller; wherein the electronic circuit board is embedded in a hot melt compound which is surrounded by an injection molded housing.

Abstract: A renal failure therapy system includes a dialysis fluid circuit including a dialysis fluid pump; a source of physiological cleaning, disinfecting, and/or decalcifying substance in fluid communication with the dialysis fluid circuit; a source of purified water in fluid communication with the dialysis fluid circuit; and a logic implementer in operable communication with the dialysis fluid pump, the logic implementer causing the physiological cleaning, disinfecting, and/or decalcifying substance from its source to be added to purified water from the purified water source to form a mixture and to circulate the mixture within the dialysis fluid circuit using the dialysis fluid pump to at least one of clean, disinfect or decalcify at least a portion of the dialysis fluid circuit without a subsequent rinse.

Abstract: A fluid filtration assembly includes a filter housing having first and second ends and a connector for fluid communication with a fluid storage vessel. A filter element is disposable within the filter housing, and first and second pumps are coupled at the first and second ends of the filter housing. A controller may coordinate the operation of the first and second pumps to induce alternating tangential flow of fluid between the filter housing and the first and second pumps. At least one of the first and second pumps is a diaphragm pump or a plunger pump. The fluid storage vessel can be a bioreactor.

Abstract: A membrane assembly for separating a feed liquid into a permeate and a retentate includes a semipermeable membrane and conductive members for applying a voltage effective for charging a semipermeable surface of the membrane, thereby reducing or preventing fouling or scaling of the membrane. The conductive members may be positioned adjacent to the semipermeable membrane, and may be configured as feed spacers or permeate spacers. Alternatively or additionally, the membrane may be electrically conductive. Power from an external source may be supplied to one or more of the conductive members, or also the membrane if conductive, which may be done wirelessly. One or more membrane assemblies may be provided in a container. One or more membrane assemblies may be provided in a stacked configuration, or wrapped around a tube in a spiral configuration.

Abstract: The present invention relates to a method of filtering an oil, the method including the following steps (A) and (B): (A) allowing a hydrophobic gas to permeate through a porous membrane including a hydrophobic polymer as a main component; and (B) allowing an oil to permeate through the porous membrane, in which the step (B) is performed after the hydrophobic gas that has permeated through the porous membrane is confirmed to have a relative humidity of 0 to 60% in the step (A).

Abstract: A portable dialysis cabinet for use in dialysis. The portable dialysis cabinet can have a size and weight that facilitates easy movement of the cabinet from one location to another with relative ease. The portable dialysis cabinet can have additional features necessary to facilitate portability, such as wheels and a handle. In general, the portable dialysis cabinet can contain all the necessary components for performing a dialysis session.

Abstract: A gas separation system for controlling a concentration of a first gas species and a second gas species in an outlet gas comprises a splitter unit. The splitter unit comprises a gas membrane system having a gas inlet port. The gas inlet port is in fluid connection with an air intake. A membrane is a selective barrier and allows some things to pass through but stops others.

Abstract: Algae harvesting and cultivating systems and methods for producing high concentrations of algae product with minimal energy. In an embodiment, a dead-end filtration system and method includes at least one tank and a plurality hollow fiber membranes positioned in the at least one tank. An algae medium is pulled through the hollow fiber membranes such that a retentate and a permeate are produced.

Abstract: A method for cleaning membrane is provided. The method includes, providing a membrane, introducing a thermo-sensitive ionic liquid to contact the membrane and perform a cleaning procedure to collect a cleaning solution, and layering the cleaning solution to form an aqueous layer and an ionic liquid layer at a specific temperature.

Abstract: A method includes producing a first blended low salinity injection water for injection into at least one injection well that penetrates a first region of an oil-bearing reservoir and producing a second blended low salinity injection water for injection into at least one injection well that penetrates a second region of an oil-bearing reservoir. The reservoir rock of the first and second regions has first and second rock compositions, respectively, that present different risks of formation damage. The first and second blended low salinity injection waters comprise variable amounts of nanofiltration permeate and reverse osmosis permeate.

Abstract: The present disclosure relates to hollow fiber tangential flow filters, including hollow fiber tangential flow depth filters, for various applications, including bioprocessing and pharmaceutical applications, systems employing such filters, and methods of filtration using the same.

Abstract: The invention relates to an undulated thermostable hollow fiber membrane of reduced wall thickness, wherein the wall thickness amounts to 20 ?m or greater and 30 ?m or less and the waveform of the hollow fiber membrane exhibits a wavelength in the range of from more than 1 mm and less than 5 mm. In particular, the invention relates to a method for producing an undulated thermostable hollow fiber membrane of lower wall thickness.

Abstract: The present invention relates to a residential home water filter system and method. The water filter system comprises a filter stage, a water purification stage, a water storage stage, and a back-up water softening stage, to deliver filtered and purified water to consumers when needed. Water from a pressurized water source first flows through filter 16 and then to a first junction 18 to a reverse osmosis system 22 when a pump 24 is activated or to an ion exchange water softener 20 when the pump 24 is deactivated. The filtered and purified water is then stored in tank 26.

Abstract: This specification describes membrane based filtration and softening systems and methods. A system has a microfiltration or ultrafiltration (MF/UF) membrane unit upstream of a nanofiltration or reverse osmosis (NF/RO) membrane unit, optionally with no intermediate tank. In some cases, the system and method may be used with feed water provided at municipal line pressure to the membranes. NF/RO permeate is collected in a tank and then pumped to a header. Treated water may be drawn from the header for use or recycled to the system, for example to backwash or flush one or both of the membrane units. In a combined process, NF/RO permeate flushes the feed side of the NF/RO unit and then backwashes the MF/UF unit. In another process, the MF/UF unit and NF/RO unit are filled with NF/RO permeate before being placed in a standby mode.

Abstract: A lighting array including one or more antimicrobial light segments configured to emit light sufficient to inactivate one or more microorganisms at a target surface may be installed within identified contamination zones of food or beverage preparation, processing, storing or packaging equipment or machinery. In an ice machine, for example, an array controller is configured for communication with an ice machine controller to receive ice machine status information signals. The status information signals are usable by the array controller to determine cycle, state, and/or usage information associated with the ice machine. The array controller may individually control activation of the one or more antimicrobial light segments based on the status information signals received from the machine controller to achieve inactivation of one or more microorganisms on target surfaces within the machine.

Abstract: A heat power management system is disclosed for an alternating current (AC) power controller for use with portable reverse osmosis water purification systems requiring precise control of a heating action for an internal water heater coupled with energy savings and the reduction of AC line disturbances. The heat power management system is designed to operate with various international electrical systems while protecting such system from excessive current draws.

Abstract: A hemodialysis machine comprising a fluid pathway for delivering a dialysate solution, wherein the fluid pathway comprises a pre-dialysis pathway and a post-dialysis pathway, a dialyser for dialysing patient's blood using the dialysate solution, the dialyser connected between the pre-dialysis pathway and the post-dialysis pathway, a first sensor system configured to sense a characteristic of the dialysate solution at a first location on the pre-dialysis pathway, a second sensor system configured to sense a characteristic of the dialysate solution at a second location on the post-dialysis pathway, and a control system configured to make a comparative analysis of the measurements taken by the first sensor and the second sensor for monitoring the composition of the dialysate solution.

Abstract: In one aspect, separation media are described herein operable for removing one or more water contaminants including NOM and derivatives thereof. Briefly, a separation medium includes a nanoparticle support and an oligomeric stationary phase forming a film on individual nanoparticles of the support, the film having thickness of 1 to 100 nm. In some embodiments, oligomeric chains of the stationary phase are covalently bonded to the individual nanoparticles.

Abstract: A filtration method that includes a cleaning step using a chemical agent, wherein provided is the filtration method with excellent chemical resistance performance. The filtration method pertaining to the present invention comprises a filtration step in which a liquid to be filtered is filtered by being passed through a porous membrane formed of a resin, and a cleaning step in which the membrane interior of the porous membrane is cleaned after the filtration step, wherein a porous membrane for which the area ratio of a resin part having an area of 1 ?m2 or less included in a cross section of the membrane interior is at least 70% of the total area of the entire resin part included in the cross section, and said cleaning step includes a step in which an aqueous solution of at least 1% sodium hydroxide is passed through the porous membrane.

Abstract: The disclosed technology includes a membrane-based device configured to concentrate black liquor, which results from papermaking. Certain embodiments may comprise a nanofiltration membrane configured to remove lignin from black liquor, and the nanofiltration membrane may include a first macroporous polymer substrate and a first graphene oxide membrane covering the first macroporous polymer substrate. Some embodiments may comprise a reverse osmosis membrane, which may include a second macroporous polymer substrate and a second graphene oxide membrane covering the second macroporous polymer substrate.

Abstract: The invention relates to a method for manufacturing a hollow fiber membrane bundle from a plurality of polysulfone and PVP-based hollow fiber membranes which encompasses the providing of a spinning solution comprising a polysulfone-based material, in particular polysulfone, a vinylpyrrolidone-based polymer, in particular polyvinylpyrrolidone, an aprotic solvent, in particular dimethylacetamide, providing a coagulant liquid comprising water and an aprotic solvent, in particular dimethylacetamide, co-extruding the spinning solution and the coagulant liquid through a concentric annular spinneret into a hollow strand, whereby the cavity of the strand is filled with coagulant liquid, conducting the strand through a precipitation gap, introducing the strand into a precipitating bath comprised substantially of water so as to obtain a hollow fiber membrane, conducting the hollow fiber membranes through at least one rinsing bath and drying the hollow fiber membrane obtained, arranging the resulting hollow fiber membra

Abstract: A method for operating a membrane separation device includes (a) setting a flow amount M(t) of permeated water and extracting the permeated water from the membrane separation device by the set flow amount M(t), and (b) temporarily stopping the extracting the permeated water, when a water level of a first water tank in which the membrane separation device is immersed, a water level of a second water tank in communication with the first tank, or a water level of a third water tank receiving overflowing water from the first water tank becomes lower than a predetermined halt water level. M(t), which is the flow amount of the permeated water during a time period t, satisfies a equation M(t)=KQ(t?1), where K is a gain (K>1), and Q(t?1) is an amount of inflow of the water-to-be-treated during a time period t?1 immediately prior to the time period t.

Abstract: A treatment device system includes a treatment machine for generating a custom dialysis solution and including at least one fluid conveyor, the treatment machine having a controller, the controller having a first memory, configured to produce the custom dialysis solution by causing the at least one fluid conveyor to mix purified water and at least one concentrate. The system also includes a user interface and a water purifier in fluid communication with and providing the purified water to the treatment machine, the water purifier including an internal central controller, the internal central controller having a second memory, to control preparation of the purified water. A server is communicatively coupled with the treatment machine and a control line provides two way communication between the controller of the treatment machine and the internal central controller of the water purifier.

Abstract: A treatment device system includes a treatment machine for performing a therapy on a patient, the treatment machine including at least one fluid conveyor and a controller, the controller having a first memory, to cause the at least one fluid conveyor to produce a therapeutic fluid by mixing purified water and at least one concentrate. The system also includes a water purifier with an internal central controller, in fluid communication with and providing the purified water to the treatment machine. A wired or wireless control line provides two way communication between the controller of the treatment machine and the internal central controller of the water purifier, the controller of the treatment machine transmitting data via the control line to the internal central controller of the water purifier for control of the water purifier, the data provided based on at least one of the operator inputs received via the user interface.

Abstract: An automated waste water treatment system includes a collection tank constructed to hold waste water, a first flow line connected to the collection tank to output the waste water from the collection tank, an electrocoagulation unit that receives the waste water and outputs the waste water as coagulated waste water to a flow line, a polymer dosage tank to provide a polymer dosage into the flow line where the polymer dosage mixes with the coagulated waste water to produce and output flocculated waste water. A clarifier connected to the flow line receives the flocculated waste water and produces sludge-free waste water and concentrated sludge, a series of filters to output filter-treated water, and an ultrafiltration system that receives filter-treated water and outputs ultrafiltration-treated water to a reverse osmosis system.

Abstract: An apparatus and a method use permeate to flush a reverse osmosis filter membrane in the same flow direction as when fluid is being filtered through the membrane. The apparatus includes a housing having a membrane positioned therein. The membrane has an interior surface and an exterior surface. The housing has an inlet port located outward of the exterior surface of the membrane and first and second outlet ports. The first outlet port is located outward of the exterior surface of the membrane and the second outlet port is located inward of the interior surface of the membrane. A first pump is used to route pressurized, untreated fluid from a fluid source through the membrane to produce permeate. A second pump is used to route permeate to a desired function while also routing some permeate at low pressure to the housing to flush the membrane.

Abstract: A method of treating a landfill leachate containing ammoniacal nitrogen and phosphate by mixing with seawater to precipitate magnesium ammonium phosphate (MAP) also known as struvite. Effects of pH, temperature, stirring speed, and magnesium to ammonia molar ratio on leachate properties such as COD, ammoniacal nitrogen, phosphate content, color, turbidity, amount of magnesium, iron and zinc are disclosed. The method provides high removal efficiency for removal of ammoniacal nitrogen, phosphate, COD, color and turbidity. The method provides a cost-effective system for treatment of landfill leachate and recovery of MAP.

Abstract: A conventional media filter such as a gravity sand filter is converted into a membrane filter. The media is removed and replaced by immersed membrane modules. Transmembrane pressure is created by a static head pressure differential, without a suction pump, thereby creating a membrane gravity filter (MGF). Preferred operating parameters include transmembrane pressure of 5-20 kPa, 1-3 backwashes per day, and a flux of 10-20 L/m2/h. The membranes are dosed with chlorine or another oxidant, preferably at 700 minutes*mg/L as Cl2 equivalent per week or less. The small oxidant does is believed to provide a porous biofilm or fouling layer without substantially removing the layer. The media filter may be modified so that backwash wastewater is removed from near the bottom of the tank rather than through backwash troughs above the membrane modules. Membrane integrity testing may be done while the tank is emptied after a backwash.

Abstract: The technology disclosed herein relates to a filter assembly. The filter assembly has a double-sided adhesive layer having a first side and a second side and defining a filter opening. A first membrane extends over the filter opening and is directly coupled to the first side of the double-sided adhesive layer about the filter opening. An adsorbent element is directly coupled to the first membrane, where the adsorbent element and the first membrane are coextensive. A second membrane encapsulates the first membrane and the adsorbent element. The second membrane is directly coupled to the first side of the double-sided adhesive layer around the first membrane and adsorbent element.

Abstract: This membrane filtration method includes: a membrane filtration process for adding a coagulant to water to be treated which contains viruses, and filtering the water to be treated by using a filtration membrane; and a cleaning process for, after the membrane filtration process, cleaning the filtration membrane, the membrane filtration process and the cleaning process being repeatedly performed, wherein, in the membrane filtration process, in the initial period of filtration, at least either an operation of filtering the water to be treated that includes the coagulant added by an amount larger than the amount of a coagulant added in a normal case, or an operation of filtering the water to be treated that has a pH lower than the pH of water to be treated in a normal case, is performed.

Abstract: An automated waste water treatment system includes a collection tank constructed to hold waste water, a first flow line connected to the collection tank to output the waste water from the collection tank, an electrocoagulation unit that receives the waste water and outputs the waste water as coagulated waste water, a polymer dosage tank to provide a polymer dosage to the coagulated waste water to produce and output flocculated waste water. An air grid of the electrocoagulation unit, the latter housing a plurality of electrodes, increases the lifespan and efficiency of the electrodes to perform electrocoagulation of the waste water. A clarifier connected to the flow line receives the flocculated waste water and produces sludge-free waste water and concentrated sludge, a series of filters to output filter-treated water, and an ultrafiltration system that receives filter-treated water and outputs ultrafiltration-treated water to a reverse osmosis system.

Abstract: Provided herein is forward osmosis-based water purification process, that includes contacting a solution of a soluble draw agent with a dehydrated insoluble draw agent, separating the now hydrated insoluble draw agent from the now concentrated draw solution, and exerting a stimulus on the hydrated insoluble draw agent for extracting water therefrom, thereby regenerating a dehydrated insoluble draw agent, wherein the osmotic concentration (osmolality) of the insoluble draw agent is greater than the osmotic concentration of the diluted draw solution, and the insoluble draw agent is impermeable to the soluble draw agent.

Abstract: An induced symbiotic osmosis system and method for treating produced fluids from a hydraulic fracturing process or system for symbiotic fluids fractionation, salinity power generation, brines and salts solution reverse osmosis. The system includes a reverse osmosis membrane assembly to create potable water from produced water. The membrane assembly includes a hollow fiber or flat sheet membrane and headers to transfer desalinated water therefrom. The system can include an electro coagulation system, an ultra or nano filtration system, and a desalter to treat the produced water or brine. A heat exchanger can be positioned between adjacent reverse osmosis membrane assemblies. An osmotic power generation unit can create electrical power by receiving and utilizing produce water and brine water from a brine storage. The system reduces the release of global warming contributing gases associated with hydraulic fracturing, while producing potable water and power.

Abstract: A modular assembly for a portable hemodialysis system may include a dialysis unit, e.g., that contains suitable components for performing hemodialysis, such as a dialyzer, one or more pumps to circulate blood through the dialyzer, a source of dialysate, and one or more pumps to circulate the dialysate through the dialyzer, and a power unit having a housing that contains suitable components for providing operating power to the pumps of the dialysis unit. The power unit may be selectively connected to the dialysis unit and provide power (e.g., pneumatic power in the form of pressure and/or vacuum) to the dialysis unit for the pumps when connected to the dialysis unit, but may be incapable of providing power to the dialysis unit when disconnected from the dialysis unit. The dialysis unit and the power unit are sized and weighted to each be carried by hand by a human.

Abstract: Apparatus and method for semi-permeable membrane cleaning in particular, applying series of pulsed water stroke, made simultaneously with osmosis backward flow causing superposed membrane directional shaking and fouling detachment. Pulsed water stroke provided by water stroke generator as several momentum sharp changes in gauge pressure and induce velocity pulse of residual brine flow. The pulsed water strokes ideally induce resonance in the membrane.

Abstract: A vibrating device for a filter-plate assembly for liquid filtration having a vessel housing for the filter-plate assembly and one or more flexible volume chambers being filled with gas. The volume chambers are adapted to expand and/or compress the volumes of the chambers inside the vessel housing allowing the liquid in the vessel chamber to move relative to the surface of the filter-plates when the vessel housing including the filter-plate assembly is subjected to a vibrating motion.

Abstract: A dosing pump (19) doses antiscalant into a membrane-based water treatment system (1). The dosing pump (19) includes a displacement body for pumping antiscalant into the membrane-based water treatment system (1) in doses. A motor drives the displacement body. A control module controls the motor. The control module is configured to vary the dosage of antiscalant pumped into the water treatment system (1) based on a temperature corrected system variable (SVTc) being based on a plurality of operating variables of the water treatment system (1).

Abstract: Methods of cleaning and sanitizing membrane modules within a membrane system are provided. A cleaning solution is circulated through the membrane system for about 2 to about 30 minutes. The cleaning solution includes organic acid and surfactant. A sanitizing solution is added to the cleaning solution to produce a boosted antimicrobial solution comprising an oxidizer. The boosted antimicrobial solution is then circulated through the membrane system for about 1 to about 20 minutes. The methods described are effective for reducing and removing bacterial spores and biofilms from membranes and improving membrane compatibility of effective cleaning and sanitizing solutions.

Abstract: A draw solute for a forward osmosis process, the draw solute comprising: a thermally responsive ionic compound having at least one of: a lower critical solution temperature (LCST) and an upper critical solution temperature (UCST), the draw solute being regeneratable from a diluted aqueous draw solution after forward osmosis via one of: liquid-liquid phase separation and solid-liquid phase separation, the draw solute being regeneratable when the diluted aqueous draw solution is at a temperature selected from one of: above the LCST and below the UCST.

Abstract: A method for treating produced water in a system for treating wastewater is disclosed. The system includes a reverse osmosis unit for removing dissolved solids. The reverse osmosis unit produces a permeate and concentrate. To reduce the fouling potential of the membranes associated with the reverse osmosis unit and/or to increase membrane lifetime and/or to increase system recovery, at least a portion of the concentrate is recycled and mixed with the wastewater stream at a point upstream of the reverse osmosis unit.

Abstract: Provided is a porous membrane which has a high water permeability performance, a high blocking performance, and a durability performance against loads of long-term and high operation pressures, which are suitable for filtering applications. The porous membrane includes one surface to be on a side of a filtrate; and the other surface to be on a side of a liquid to be filtered, wherein a surface pore diameter index of the one surface is 2.5 or more, the surface pore diameter index being determined by dividing a pore diameter in a top surface by a pore diameter in a second top surface.

Abstract: Peroxyformic acid compositions for removal of biofilm growth and mineral deposits on membranes are disclosed. In particular, peroxyformic acid compositions are generated in situ or on site generation for the reduction and prevention, of biofilms and the mitigation of mineral buildup on the membranes. The compositions according to the invention are compatible with the membranes under application of use conditions.

Abstract: A system for and method of cleaning polymeric and ceramic microfiltration and ultrafiltration membranes in hollow fiber, flat sheet, and tubular membrane units is provided. The method includes using a reducing agent, specifically ascorbic acid, based formulation. The method also includes certain protocols useful in conducting such cleanings. The system includes features for facilitating the method of the present invention.

Abstract: The porous hollow-fiber membrane of the present invention comprises a fluororesin polymer, and has columnar structures oriented in the longitudinal direction thereof. In the porous hollow-fiber membrane, molecular chains of the fluororesin polymer have been oriented in the longitudinal direction of the porous hollow-fiber membrane and have an average value ? of Raman orientation parameter of 1.5-4.0.

Abstract: A filter arrangement with a top element and a bottom element and a filter element therebetween captures oversized particles on the upper surface of the filter element and tangentially rinses these particles using an elution fluid to provide a concentration of particles in a relatively low volume of fluid for further analysis. In an intermediate step, the particles captured by the filter may be rinsed with a rinsing fluid such as water to pass additional undersized particles through the filter, thereby providing a purer sample. To improve efficiency, check valves may be used for passageways with one-way flow. Additionally, a configuration of three-way stopcocks may also be utilized. Finally, a sandwich arrangement is possible, wherein a single bottom element is sandwiched between two opposing top elements.

Abstract: A membrane separation process is described. The process comprises pumping of a fluid stream through a membrane module to produce a permeate during a plurality of membrane operating cycles. Each membrane operating cycle comprises a filtration cycle and a relaxation cycle. Concentration polarisation is controlled during the process by controlling duration of filtration cycles and relaxation cycles to relatively short duration to maintain the degree of concentration polarisation below a target.

Abstract: A membrane filtration system with reverse osmosis (RO) or nanofiltration (NF) elements is adapted to provide high recovery from difficult wastewater. The system has a plurality of stages. The system is configured to provide concentrate staging. The last stage also has concentrate recirculation. The valves and pumps of the system are arranged such that the order of flow and a recirculation pump may be switched between the first stage and the last stage at some times.