Provided is a cleaning agent capable of preventing a reduction in the rejection rate of an RO membrane which may occur when the membrane is cleaned, the cleaning agent including a membrane protectant that is a basic or hydrophobic amino acid, a peptide containing the amino acid as a constituent amino acid, or a derivative of the amino acid or the peptide. The cleaning agent may further include at least one agent selected from the group consisting of an alkaline agent, a combined chlorine agent, and an oxidizing agent. The amino acid is preferably arginine, lysine, or phenylalanine. Also provided are a cleaning liquid that is an aqueous solution produced by diluting the cleaning agent and a method for cleaning a reverse osmosis membrane with the cleaning liquid.

Method for treating water for the purpose of reducing the content of organic matter, of micropollutants and of pathogenic agents therein, comprising the supplying of water to be treated directly into a membrane reactor containing at least one filtration membrane and an adsorbent material, stirring the mixture of water and adsorbent, and extracting treated water, characterised in that the adsorbent material consists of micrograins of activated carbon having a real density of at least 0.45, a settling velocity of 30 to 50 m/H, a specific surface area of 400 to 2500 m.sup.2/g, and an average particle size of between 600 and 1300 m, less than 5% by volume of said grains having a size of less than 400 m, in that the concentration of said activated carbon micrograins in said membrane reactor is maintained between 5 and 100 g/L, and in that no other granular or particulate material other than the activated carbon micrograins is used in said reactor, the stirring of said mixture of water and activated carbon micrograins in the membrane reactor being at least partially carried out by air injection into said mixture at a rate of 30 to 60 Nm.sup.3/m.sup.2.Math.H and being sufficiently vigorous to avoid the deposit of activated carbon micrograins on said at least one filtration membrane

Disclosed herein are apparatuses and methods for semi-permeable membrane cleaning. In particular, a pressure retarded osmosis (PRO) process redirects raw solution and fluid streams in such a way as to cause periodic changes of the process from PRO to reverse osmosis (RO) for lifting and detaching fouling. Further disclosed is applying, at least periodically, a pulsed-flow regime in the fluid stream, thereby causing increased shearing force for enhanced evacuation of the foulant. Additionally, a backward wash may be provided by injection, for a predetermined injection time, of additional solution selected in such way that net driving pressure becomes RO opposite to normal PRO operation, thereby providing a backward flow from a first side of the membrane to a second side of the membrane, so as to lift and evacuate foulant.

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/m.sup.2/h. The membranes are dosed with chlorine or another oxidant, preferably at 700 minutes*mg/L as Cl.sub.2 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.

A cleaning method for a water treatment membrane (2) provided with a primary surface (2a) for inflow of untreated water and a secondary' surface (2b) for outflow of treated water, the method including a first cleaning step of bringing a first cleaning fluid containing a metal eluent into contact with at least the primary surface and eliminating metallic scale (11) attached to the water treatment membrane, and then a second cleaning step for bringing a second cleaning fluid containing an oxidizing agent into contact with at least the primary surface and eliminating organic scale (12) attached to the water treatment membrane.

A method of producing a sugar liquid includes filtering a cellulose-derived sugar liquid through one or more separation membranes selected from the group consisting of an ultrafiltration membrane, a nanofiltration membrane and a reverse osmosis membrane, and washing the separation membrane(s) after filtration with washing water containing an acidic substance and an aromatic compound.

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 method and a composition of cleaning and reprocessing a hemodialysis filtration membrane assembly that employs polyvinylpyrrolidone-containing membranes, the method comprising the step of treating the assembly with an aqueous mixture or a gas-liquid mixture comprising an inorganic base and from 100 to 1,000 ppm of a hypochlorite salt, wherein the mixture has a pH between about 12.0 and about 12.5, an oxidation reduction potential of less than 0.5 volts, a temperature of 40 to 55 C. and wherein the mole % of hypochlorous acid, HOCl, relative to the sum of hypochlorous acid plus hypochlorite anion, OCl, is less than 0.004%.

A combined chlorine agent having a low concentration of free chlorine and a high concentration of combined chlorine whereby the combined chlorine concentration of water can be increased when added to water systems at a low concentration of free chlorine. The combined chlorine agent is an aqueous agent which contains an alkali metal hydroxide, sulfamic acid, and an oxidizing agent based on chlorine, wherein the compositional ratio of the oxidizing agent based on chlorine to the sulfamic acid is in the range from 0.45 to 0.6 by Cl/N (mole ratio), the compositional ratio of the oxidizing agent based on chlorine to alkali is in the range from 0.3 to 0.4 by Cl/alkali metal (mole ratio), and the free chlorine concentration in the aqueous agent is 2% by weight or lower of the total chlorine concentration.

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.