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.

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 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 operating a reverse osmosis membrane device, a slime control method that is applied to a reverse osmosis membrane device, and a water treatment device are provided. The method comprises: a first step for intermittently adding an oxidation-based slime inhibitor and intermittently supplying water to be treated containing the oxidation-based slime inhibitor to a reverse osmosis membrane device; and a second step for adding an organic-based slime inhibitor at least during a period other than the addition period of the first step and supplying the water to be treated containing the organic-based slime inhibitor to the reverse osmosis membrane device.

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 chemical for membranes, which contains a polymer compound having a carboxyl group and a sulfo group, preferably a polymer compound represented by formula (1). A membrane treatment method wherein this water treatment chemical for membranes is added to membrane feed water when water to be treated, which contains an organic compound having a phenolic hydroxy group, is subjected to a membrane separation treatment. ##STR00001## In the formula, m and n represent molar percentages of respective structural units; (m+n) is 90-100%; and R represents an anionic group containing a sulfo group.

Provided is a water treatment method with which, in a reverse osmosis membrane treatment conducted on water being treated that contains chlorine-based oxidants and/or bromine-based oxidants, or on water being treated that contains iodide ions, it is possible to suppress any deterioration in a reverse osmosis membrane and to suppress the formation of slime. This water treatment method includes a reverse osmosis membrane treatment, the water treatment method involving: adding, to water being treated that contains chlorine-based oxidants and/or bromine-based oxidants, 1 mol or more of iodide ions per mole of the free chlorine content and free bromine content of the water being treated; or adding, to water being treated that contains iodide ions, a chlorine-based oxidant and/or a bromine-based oxidant such that the free chlorine content and free bromine content reach 1 mol or less per mole of iodide ions in the water being treated.

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.

The present invention relates to a computer-readable recording medium having recorded thereon a clogging location determination program for a separation membrane module, in which, in order to determine a clogging location of a separation membrane module in a fresh water generation system for obtaining treated water by filtrating water to be treated by a separation membrane module having a separation membrane, a computer is caused to function as a clogging location determination means for determining a clogging location of the separation membrane module from a resistance in a lower part of the separation membrane module, a filtration resistance of a hollow-fiber membrane, and a resistance in an upper part of the separation membrane module.