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 calcium and/or magnesium additive for membrane fouling control made up of particles for forming a dynamic protective layer on the membrane for fouling control of the membrane, when added in the liquid flowing through the membrane, wherein the particles are synthetic mineral precipitate particles based on calcium and/or magnesium selected from the group consisting of ultrafine synthetic mineral precipitate particles and microfine synthetic mineral precipitate particles, as well as a process and system for membrane fouling control.

A system for membrane fouling control configured to run one or more filter cycles, wherein each filter cycle of the one or more filter cycles includes an operation mode and a cleaning mode. The system includes: a first conduct portion; a second conduct portion; a membrane arranged between the first conduct portion and the second conduct portion. The membrane is configured in the operation mode to filter a liquid to be filtered by conducting it from the first conduct portion to the second conduct portion. A fouling control means filled with fouling control particles is added in the operation mode in the first conduct portion so that a dynamic protective layer is formed on the membrane. The fouling control particles are mineral particles based on calcium and/or magnesium.

A system for membrane fouling control configured to run one or more filter cycles, wherein each filter cycle of the one or more filter cycles includes an operation mode and a cleaning mode. The system includes: a first conduct portion; a second conduct portion; a membrane arranged between the first conduct portion and the second conduct portion. The membrane is configured in the operation mode to filter a liquid to be filtered by conducting it from the first conduct portion to the second conduct portion. A fouling control means filled with fouling control particles is added in the operation mode in the first conduct portion so that a dynamic protective layer is formed on the membrane. The fouling control particles are mineral particles based on calcium and/or magnesium.

A separation recovery system for separating and recovering an object to be separated includes a metal porous membrane which has a first principal surface and a second principal surface facing the first principal surface and has a plurality of through-holes extending between the first principal surface and the second principal surface, a supply device which supplies a first fluid containing the object to be separated from the first principal surface of the metal porous membrane toward the second principal surface, and a backwash device which supplies a second fluid containing a plurality of particles larger than a size of the plurality of through-holes of the metal porous membrane in a direction from the second principal surface of the metal porous membrane toward the first principal surface.

Surfactants capable of releasing and/or dissolving polymers to form water-soluble or water-dispersible polymer solutions are disclosed. In addition, polymer compositions containing a water-in-oil emulsion comprising the surfactant are provided and can be used, for example, in methods of dissolving a polymer. Also disclosed are detergent compositions and methods of cleaning articles and/or membranes using the surfactants herein. These surfactants and polymer compositions can be used in various industries including for water clarification, papermaking, sewage and industrial water treatment, drilling mud stabilizers, and enhanced oil recovery.

Surfactants capable of releasing and/or dissolving polymers to form water-soluble or water-dispersible polymer solutions are disclosed. In addition, polymer compositions containing a water-in-oil emulsion comprising the surfactant are provided and can be used, for example, in methods of dissolving a polymer. Also disclosed are detergent compositions and methods of cleaning articles and/or membranes using the surfactants herein. These surfactants and polymer compositions can be used in various industries including for water clarification, papermaking, sewage and industrial water treatment, drilling mud stabilizers, and enhanced oil recovery.

Described herein is a method of using hollow fiber filter cartridge. The method includes: providing a hollow fiber filter cartridge inside or outside an environmental cleaning equipment; allowing a wastewater to enter the hollow fiber filter cartridge from an outside of the hollow fiber filter under no water pressure or low water pressure (such as under 30 gw/cm.sup.2); allowing the wastewater to cross a plurality of nanopores of the hollow fiber filter cartridge under no water pressure or low water pressure (such as under 30 gw/cm.sup.2) to produce a clean water; and allowing the environmental cleaning equipment to filter wastewater to produce clean water continuously, thereby improving cleaning efficiency and reducing water consumption.

Described herein is a method of using hollow fiber filter cartridge. The method includes: providing a hollow fiber filter cartridge inside or outside an environmental cleaning equipment; allowing a wastewater to enter the hollow fiber filter cartridge from an outside of the hollow fiber filter under no water pressure or low water pressure (such as under 30 gw/cm.sup.2); allowing the wastewater to cross a plurality of nanopores of the hollow fiber filter cartridge under no water pressure or low water pressure (such as under 30 gw/cm.sup.2) to produce a clean water; and allowing the environmental cleaning equipment to filter wastewater to produce clean water continuously, thereby improving cleaning efficiency and reducing water consumption.

The present disclosure relates to a water purification apparatus that comprises a reverse osmosis device, RO-device, producing a purified water flow and to a corresponding method. The proposed method comprises detecting at least one fluid property of purified water in the purified water path and regulating a flow rate of water in the recirculation path to fulfill one or more predetermined criteria of the purified water in the purified water path, based on the at least one detected fluid property. The present disclosure also relates to a computer program and a computer program product implementing the method.