A method for controlling slime is used in a reverse osmosis membrane apparatus and has a water-supplying step of supplying water to be treated to the reverse osmosis membrane. The water-supplying step includes a first water-supplying step in which a slime controlling agent X which contains 2,2-dibromo-3-nitrilopropionamide (DBNPA) and a slime controlling agent Y which contains at least one type selected from a group consisting of components (A) to (D) are added to the water to be treated which has a pH of 10 or less, and the water to be treated which contains the slime controlling agent X and the slime controlling agent Y is supplied to the reverse osmosis membrane. The component (A) is mixture of 5-chloro-2-methyl-4-isothiazolin-3-one (Cl-MIT) and 2-methyl-4-isothiazolin-3-one (MIT), the component (B) is chloramine compound, the component (C) is stabilized bromide, and the component (D) is glutaraldehyde.

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.

Provided is an agent and a liquid for cleaning an RO membrane to remove effectively foulants that can not be sufficiently removed with conventional cleaning agents when an RO membrane particularly an aromatic polyamide RO membrane has been used for water treatment and has become fouled resulting in degradation of performance such as permeation flux, pressure difference, and salt rejection rate. The agent for cleaning an RO membrane includes an aliphatic amide and/or an aromatic amide. Also provided is a method for cleaning an RO membrane with the cleaning agent or the cleaning liquid. The aliphatic amide and/or the aromatic amide particularly an aliphatic amide and/or an aromatic amide being soluble in water and having a relatively low molecular weight remove effectively foulants adhered on an aromatic polyamide RO membrane.

A composition is disclosed for cleaning a membrane. The composition includes: (i) a non-ionic surfactant having the formula: RO(CH.sub.2CH.sub.2O).sub.nH, wherein R is a branched, substituted or unsubstituted, C.sub.11-15 alkyl group, wherein n is an average degree of ethoxylation, and wherein n is in the range of from 3 to 20; and (ii) at least one of an additional non-ionic surfactant, a water soluble solvent, or a hydrotrope. In one version of the composition, an upper limit of a range of molecular weights of the surfactant is 1300 grams or below. In another version of the composition, the composition has a gel point such that it will be in the liquid phase before and after dilution with any amount of water at all temperatures of 40 F. and above. A method of cleaning a membrane using the compositions is also disclosed.

Provided is a water treatment method, in which a cycle including: a filtration step of filtering water to be treated through a separation membrane from a primary side to a secondary side of the separation membrane; and a backwashing step of washing the separation membrane from the secondary side to the primary side is repeated, the water treatment method including the steps of: injecting, into the separation membrane, ozone to be used in the backwashing step; and when, of the repeated cycles, a previous cycle is defined as a first cycle and a following cycle subsequent to the first cycle is defined as a second cycle, setting an ozone injection amount to be injected in the second cycle to a value equal to or less than an ozone injection amount injected in the first cycle.

This invention is directed to filtration system, filtration apparatus and methods of use thereof, wherein the filtration system comprises a solid support, perylene diimide based membrane layer and a polymer, specifically a Nafion polymer. The system and apparatus of this invention enables filtration of solutes such as: dyes, salts, heavy metal ions, pharmaceuticals and small organic molecules.

An agent for cleaning an RO membrane, which includes an aldonic acid and/or a salt of an aldonic acid, removes effectively foulants that cannot be sufficiently removed with conventional cleaning agents when an RO membrane used for water treatment. In a method for cleaning an RO membrane with the cleaning agent or the cleaning liquid, while the detachment and hydrolysis effects are achieved by performing cleaning under alkaline conditions, chelation of heavy metals is caused by the aldonic acid and/or the salt of an aldonic acid. When an anionic surfactant is used in combination with the aldonic acid and/or the salt of an aldonic acid, the anionic surfactant causes the detachment of foulants. When a polyol having a molecular weight of 1000 or less is used in combination with the aldonic acid and/or the salt of an aldonic acid, the polyol causes wetting and swelling of foulants.

Disclosed are devices, methods and/or systems for use in protecting items and/or structures that are exposed to, submerged and/or partially submerged in aquatic environments from contamination and/or fouling due to the incursion and/or colonization by specific types and/or kinds of biologic organisms and/or plants, including the protection from micro- and/or macro-fouling for extended periods of time of exposure to aquatic environments.

A hollow fiber membrane module 100 includes: a plurality of hollow fiber membranes 10; a container 20 storing the plurality of hollow fiber membranes 10; and a feed water inlet 201 provided at one end portion of the container 20 such that a direction in which feed water flows into the container 20 is parallel to a longitudinal direction of the plurality of hollow fiber membranes 10. A permeation flux of the hollow fiber membranes 10 at a transmembrane pressure difference of 0.1 MPa is higher than or equal to 850 liter/m.sup.2/h.

Methods and systems for preventing biofouling of membranes utilized in water treatment processes (i.e., water treatment membranes) are described. Methods include X-ray excitation of luminescent materials capable of emitting in the violet to UV range (e.g., from about 180 nm to about 440 nm). X-rays are directed at water treatment modules to contact the luminescent materials within the modules and excite internal violet/UV to prevent biofouling of membranes. The methods can be utilized in conjunction with existing processing equipment and can prevent biofouling of water treatment membranes in high volume treatment processes in an environmentally friendly fashion.