A method for cleaning a filter membrane in which at least 2 types of cleaning water containing oxidizing agents are prepared, and the filter membrane is cleaned using the cleaning water in an ascending order of the oxidizabilities of the oxidizing agents. Moreover, an apparatus for cleaning a filter membrane of the present invention comprises a means for cleaning the filter membrane using at least 2 types of cleaning water containing oxidizing agents, and the filter membrane is cleaned using the cleaning water in an ascending order of the oxidizabilities of the oxidizing agents. The method and the apparatus for cleaning a filter membrane can efficiently remove polluting substances adhered to a filter membrane while reducing the amounts of oxidizing agents and water to be used, and can maintain the filtration performance for a long period of time.

A polyamide (PA) nanofiltration (NF) membrane and a preparation method thereof by regeneration from a scrapped microfiltration (MF) membrane are provided. The method adopts a cleaning-repairing-interfacial polymerization upgrading strategy, where, sodium hypochlorite and oxalic acid are used for deeply cleaning a scrapped MF membrane. PDA is used as a repairing agent to construct a reaction platform on the membrane surface, and finally a reaction system of piperazine and trimesoyl chloride (TMC) are used to form a PA NF membrane with a PA active layer. The repairing can construct a coating with a given thickness and prominent hydrophilicity on the membrane surface, which provides favorable base membrane conditions for upgrading and preparing an NF membrane.

A water treatment device includes a sub-reverse osmosis membrane device having a primary casing and a primary reverse osmosis membrane dividing the primary casing into a primary liquid passing part and a primary permeating part; a low pressure water feed pump feeding seawater to the primary liquid passing part at a pressure that is equal to or lower than an osmotic pressure of the seawater; a main reverse osmosis membrane device having a secondary casing and a secondary reverse osmosis membrane dividing an inside of the secondary casing into a secondary liquid passing part and a secondary permeating part; and a high pressure water feed pump feeding a primary treated liquid, which is a resultant product of the seawater passing through and flowing out of the primary liquid passing part, to the secondary liquid passing part at a pressure higher than an osmotic pressure of the primary treated liquid.

Disclosed are detergent compositions and methods of cleaning articles and/or membranes using the surfactants herein. Compounds, compositions, and methods for using these compounds and compositions in detergent or cleaning compositions are also provided. These compounds, compositions, and methods are particularly directed to cleaning compositions and methods that have advantageous cleaning properties at a pH of 7 or less. In particular, the compounds, compositions, and methods described herein can also be used as general surfactants in detergent compositions or in methods of cleaning articles or membranes.

A circulating water preparation system for cooling plants, a cooling system, in particular a recooling system, and a method for operating such a cooling system. In such a cooling system a surface of a heat exchanger is cooled by wetting with water, the water is collected in a collecting tank and returned by means of a water circuit for the renewed wetting of the surface of the heat exchanger. The method is characterised in that the water is purified by means of a filter, in particular a membrane filter. As a result considerably less biocide is needed to keep the water free of germs, in particular legionella, compared to conventional cooling systems or methods for operating such cooling systems.

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 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.

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.

The present disclosure relates to a conjugated polyelectrolyte-grafted membrane, which is obtained by fixing a conjugated polyelectrolyte (CPE) capable of generating active oxygen under visible light irradiation to a membrane through crosslinking, and can remove contaminants in water, while reducing bio-fouling on the surface of the membrane, by generating active oxygen through a photocatalytic reaction of the conjugated polyelectrolyte (CPE), as well as to a method for manufacturing the same. The method for manufacturing a conjugated polyelectrolyte-grafted membrane includes the steps of: preparing a conjugated polyelectrolyte (CPE); coating a conjugated polyelectrolyte (CPE) on the surface of a membrane; and carrying out crosslinking of the conjugated polyelectrolyte (CPE) with the surface of the membrane.

A non-oxidizing, buffered disinfectant concentrate is provided to be included in a solution used to disinfect a membrane. The solution applied to the membrane is configured to have a pH that is compatible with the membrane. The disinfectant concentrate includes an aqueous solvent; a hydrotrope; a strong acid surface cleanser; a biocidal active, preferably, at least two biocidal actives; a buffer agent; and, optionally, an anionic surfactant. The biodical active may be selected to function both as a biocide and as a weak acid/buffer combination. A disinfectant solution applied to the membrane includes from about 0.1 wt % to about 3.5 wt % of this disinfectant concentrate.