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 method is disclosed for scaling control in a membrane system operation. The method can be performed by a model in the control system of a plant. The method can include selecting one or more antiscalants corresponding to one or more components of the scale, based on one or more of feed water condition, membrane material, membrane fouling status and a kinetic study relating to a reaction between the antiscalants and the components of the scale. The composition of one or more selected antiscalants can be estimated based on an overall scaling rate constant.

The present invention relates to a fresh water generation method including: feeding raw water or pretreated water thereof as feed water into a semipermeable membrane module in a pressurized state using a booster pump, thereby separating the feed water into a concentrate and a permeate having a low concentration, in which a scale inhibitor having a reducing function is dosed intermittently or continuously upstream from the semipermeable membrane module, thereby inhibiting scale generation and maintaining an oxidation-reduction potential of at least either the feed water or the concentrate to a threshold value or lower.

The present invention includes a method of cleaning a membrane contactor comprising: connecting a membrane contactor having a first and a second surface, the membrane contactor being in liquid communication with a first and a second liquid circulation loop; rerouting the source of oil-containing liquid from the membrane contactor; draining the oil-containing liquid in contact with the first surface of the membrane contactor via a drain; circulating a cleaning oil over the first surface of the membrane contactor; pumping a collection fluid over the second surface of the membrane contactor; and contacting the oil-containing liquid with the first surface of the membrane contactor under pressure to maximize oil coalescence at the first surface of the membrane contactor while also circulating the collection fluid over the second surface of the membrane contactor to capture the coalesced oil.

An electrochemical wastewater treatment system comprises a reactor tank, an electrochemical reactor and a separation device which filters the effluent stream from the reactor tank and generates a treated wastewater stream and a reject stream which is at least partially fed to the electrochemical reactor or to the reactor tank to thereby increase the concentration of selected soluble and insoluble compounds within the reactor. A portion of the reject stream or a portion of the wastewater in the reactor tank can be discharged as a blowdown stream. Flow control means are provided for adjusting the volume of the reject stream and of the blowdown stream for controlling the compounds concentration. The concentration of soluble and insoluble compounds in the reactor is therefore decoupled from the concentration of the compounds in the reactor effluent stream to achieve an improved reactor performance and a higher quality effluent.

Membrane filtration systems can be used to purify liquid streams for downstream use. In practice, foulant can build-up on the surface of a membrane within a filtration system over time. The effectiveness of the filtration system will deteriorate if the fouling is not properly controlled. In some examples, a method of controlling membrane fouling in a pressurized membrane system involves supplying a feed stream that is predominately air mixed with water to the membrane. In other words, the feed stream a greater volume of air than water, even though it is the water being processed by the membrane. Supplying the pressurized membrane system with a feed stream that contains a greater volume of air than water can yield significantly better performance than supplying the membrane with a feed stream that contains a greater volume of water than air.

The present disclosure is directed to filtering technologies that combine elements of continuous and batch NF/RO based on the constraints of the end-user facility to achieve a target balance between, for instance, recovery and power consumption, and to reduce long term operating cost of a plant. A method for extending batch operation into a second induction period with antiscalant injection is also disclosed herein, with the second induction period allowing for yet higher water recovery.

A method of inhibiting scale in an industrial water system includes the steps of dosing the industrial water system with a water treatment polymer comprising at least 10 mol % of carboxylic acid monomer and a quaternized naphthalimide fluorescent monomer as disclosed herein, and then monitoring the fluorescence of the water system. The polymers are also useful for flocculation and coagulation in wastewater treatment.

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.