An example water purification system for purifying high concentration feed solutions includes a high rejection forward osmosis module, one or more low rejection modules, and a high rejection reverse osmosis module. The low rejection modules may have different rejection levels. The system may be pressurized by one or more pumps. One or more of the low rejection modules may include one or more nanofiltration (NF) membranes. The draw solution may comprise a monovalent salt, a multivalent salt, or a combination of both.

A water treatment system is provided. The system includes a prefiltration unit for filtering the untreated water in fluid communication with a source of untreated water. The prefiltration unit produces a prefiltered water from the untreated water. A pump in fluid communication with the prefiltration unit can selectively increase the flow rate of the prefiltered water in a first line, the first line in fluid communication with a membrane element. The membrane element produces a permeate and a retentate from the prefiltered water, the permeate being imparted with a lower concentration of solutes than the retentate. A tank in fluid communication with the membrane element and the prefiltration unit stores prefiltered water from the prefiltration unit and the permeate from the membrane element. One or more valves regulate the flow of prefiltered water and the permeate, and one or more sensors can measure characteristics of the prefiltered water.

The water treatment device according to the present disclosure includes: an electrochemical cell having electrodes including a positive electrode and a negative electrode, and a bipolar membrane; a tank; a power supply configured to apply power to the electrodes; a water circulation flow path having at least the tank and the electrochemical cell and through which water circulates; a circulation device configured to circulate water in the water circulation flow path; a raw water supply path configured to supply raw water to the water circulation flow path; and a control device. In performing water softening treatment in the electrochemical cell where power is applied to the electrodes so as to remove ions from raw water and soft water is produced, the control device drives the circulation device so as to circulate water in the water circulation flow path.

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).

Provided is a scale inhibitor for RO membranes which effectively inhibits the precipitation of calcium carbonate in an RO membrane treatment without increasing the phosphorus concentration in effluent and which can be used even in the RO membrane treatment of feed in which high-M-alkalinity concentrate having a calcium hardness level of 100 to 600 mg/L-CaCO.sub.3 and an M alkalinity of 1000 to 16000 mg-CaCO.sub.3/L is produced. A scale inhibitor for reverse osmosis membranes which inhibits the formation of calcium carbonate scale in an RO membrane treatment, the scale inhibitor including components (A) and (B) below. An RO membrane treatment method including adding the scale inhibitor for RO membranes to RO feed. Component (A): Terpolymer of maleic acid, an acrylic acid alkyl ester, and vinyl acetate, Component (B): Homopolymer of carboxylic acid

A filtration membrane coating comprising a hydrophilic polymer, a surfactant, and one or more charged compounds, each containing one or more sulfonate functionalities and one or more linkable functionalities selected from the group consisting of amine, monochlorotriazine, and dichlorotriazine. The hydrophilic polymer and surfactant form a thin primer layer which is also superhydrophilic. The primer layer improves flux, and enables improved adhesion of the one or more charged compounds, which form a charged dye layer on top of the primer layer when enhances rejection of charged divalent ions. The coating can be applied while the membrane is packaged in its final form, such as in a spiral wound or other configuration.

A method for inhibiting silica scale formation in an aqueous system by adding a hydrophobically-modified alkylene oxide urethane copolymer anti-scalant to the water used in the aqueous system.

A water desalination system includes a first set of ultrafiltration membranes, a second set of ultrafiltration membranes, a first backwashing system configured to treat at least one of the first set of ultrafiltration membranes or the second set of ultrafiltration membranes with brine generated by a reverse osmosis process, and a second backwashing system configured to treat at least one of the first set of ultrafiltration membranes or the second set of ultrafiltration membranes with one or more chemicals and reverse osmosis permeate water.

A control method for a water purifier includes establishing a first cleaning passage which communicates a scale inhibiting mechanism with an RO membrane element of the water purifier and through which the scale inhibiting mechanism cleans the RO membrane element for a first preset time. The method additionally includes establishing a draining passage which is connected to the scale inhibiting mechanism and through which liquid in the scale inhibiting mechanism is drained out, and establishing a second cleaning passage which is in communication with raw water and through which the RO membrane element is cleaned with the raw water for a second preset time.

In order to efficiently transport a filtration target liquid to a separation membrane module and to facilitate additional simplification of equipment in a filtration device including the separation membrane modules in which a plurality of lines thereof are disposed in series, a filtration device according to the present invention is a filtration device including a plurality of separation membrane modules each of which separates a liquid to be filtrated into a permeated liquid and a non-permeated liquid, in which the filtration device includes: a series non-permeated liquid flow channel that forms a series unit by connecting non-permeation sides of the plurality of separation membrane modules in series; and a parallel permeated liquid flow channel that forms a parallel unit by connecting permeation sides of the plurality of separation membrane modules in parallel.