Showing papers on "Reverse osmosis published in 1998"

Composite polyamide reverse osmosis membrane and method of producing the same

Abstract: A composite polyamide reverse osmosis membrane and method of producing same. In a preferred embodiment, the membrane is made by coating a porous polysulfone support with an aqueous solution containing 2 wt % m-phenylenediamine (MPD), and 0.1 wt % di(ethylene glycol) hexyl methyl ether. Next, the excess solution is removed, and the coated support is dipped in 0.1 wt % organic solvent solution of trimesoyl chloride (TMC) in a mixture of alkanes having from 8 to 12 carbon atoms. After draining the TMC solution off, the resulting composite membrane is air dried and then rinsed in a basic aqueous solution. The resultant membrane exhibits a flux of 21.3 gfd and a salt rejection of 98.9% when used at 225 psi for an aqueous solution containing 2000 ppm of NaCl.

Desalination method and apparatus utilizing nanofiltration and reverse osmosis membranes

Abstract: Apparatus and methods for producing potable water from an aqueous feed such as seawater utilizing a pressure vessel designed for operation in the range of about 250 psig to about 350 psig having reverse osmosis (RO) separation elements disposed upstream of at least one nanofiltrate separation element. The supply of seawater at such pressure creates no permeate flow through the RO membranes, so the seawater flushes the feed side of the RO elements on its way to the NF element where very substantial permeate flux occurs, producing a NF permeate substantially depleted in divalent ions and optionally moderately depleted in monovalent ions. The NF permeate is collected in a holding tank having liquid level switches, and when a desired level is reached, a control system causes the pump to draw suction from the holding tank while shutting off feed from the seawater source. When the NF permeate is supplied to the feed side of the RO elements, its osmotic pressure is such that substantial RO permeation now occurs creating a stream of good quality potable water. During both stages of operation, energy is conserved by routing the concentrate stream leaving the pressure vessel through an energy recovery device that boosts the pressure of the liquid being discharged from the positive displacement pump.

Counter top reverse osmosis water purification system

Abstract: A counter top reverse osmosis water purification system, suitable for home use, is connected to a water supply and contains a closed fluid treatment circuit extending to a water outlet. The closed fluid circuit flows through a plurality of replaceable water treatment modules mounted on a flowboard and each having a specific water treatment function, such as the removal of a particular material from the water by the use of reverse osmosis, filtration, carbon adsorption, ion exchange or the addition of a chemical to balance the desired water conditions. Preferably the circuit also includes traversing a radiation device, for example an ultraviolet light, for the purpose of sanitizing the water.

Portable reverse osmosis unit for producing drinking water

Abstract: A method of purifying impure water to provide drinking water using an apparatus, the method comprising the steps of providing a microfiltration unit (14, 20), a reverse osmosis unit (70) and a CIP (clean-in-place) tank (100) containing retentate interconnected to permit backflushing the microfiltration filter (20) with retentate and continued or interrupted operation of the reverse osmosis unit (70) by directing retentate thereto

Effects of the polyamide molecular structure on the performance of reverse osmosis membranes

Abstract: Thin-film composite reverse osmosis membranes of polyamides were prepared by interfacial polymerization. Various benzenediamines and poly(aminostyrene) were interfacially reacted with various acyl chlorides to prepare a skin layer of composite membranes. Among the membranes prepared from the structural isomeric monomers of benzenediamines and acyl chlorides, i.e., the same chemical composition but different in the position of functional groups on the aromatic ring, the membrane with the best salt rejection was obtained when the reacting groups forming amide are located at the same position on the aromatic ring. Membranes prepared by interfacially reacting various diamines with trimesoyl chloride revealed that the salt rejection depends on the linear chain structure of polyamides and network formed by crosslinking. Membranes obtained by interfacial polymerization of poly(aminostyrene) with trimesoyl chloride showed higher water flux but lower salt rejection than those obtained by interfacial polymerization of various benzenediamines with trimesoyl chloride. Membranes obtained here showed the typical trade-off behavior between salt rejection and water flux. However, membranes prepared by interfacially reacting trimesoyl chloride with a mixture of poly(aminostyrene) and m-phenylenediamine or a mixture of poly(aminostyrene), m-phenylenediamine, and diaminobenzoic acid showed a performance advantage over usual membranes, i.e., a large positive deviation from the usual trade-off trend. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1821–1830, 1998

Process for desalination of saline water, especially sea water, having increased product yield and quality

Abstract: A desalination process is disclosed which combines two or more substantially different water treatment processes in an unique manner to desalinate saline water, especially sea water, to produce a high yield of high quality fresh water, including potable water, at an energy consumption equivalent to or less than much less efficient prior art desalination processes. In this process a nanofiltration step is synergistically combined with at least one of sea water reverse osmosis, multistage flash distillation, multieffect distillation of vapor compression distillation to provide an integrated desalination system by which sea water can be efficiently and economically converted to high quality potable water in yields which are at least 70 %-80 % greater than the yields available from the prior art processes. Typically a process of this invention using the nanofiltration initial step will produce, with respect to sea water feed properties, calcium, magnesium, sulfate and bicarbonate ion content reductions of 63 %-94 %, pH decreases of about 0.4-0.5 units and total dissolved solids content reductions of 35 %-50 %.

Treatment of composite polyamide membranes to improve performance

Abstract: Composite polyamide reverse osmosis membranes are treated with an aqueous chlorinating agent at a concentration of 200 to 10,000 ppm for a time sufficient to improve flux, lower salt passage and increase the stability to base. In a preferred embodiment the membrane is treated with heated water at temperature of 40 °C to 100 °C before being exposed to the chlorine treatment.

Method and plant for the treatment of liquid organic waste

Abstract: A method and plant for the treatment of an organic waste material in liquid form, e.g. liquid manure from livestock, the method comprising filtering fibres and particles from the liquid, subjecting the liquid to anaerobic fermentation in a biogas reactor, separating a substantially sterile and particle-free permeate stream from the biogas reactor, e.g. using ultrafiltration, subjecting the permeate stream to treatment with an ammonia stripper at an elevated temperature and preferably at reduced pressure to remove substantially all ammonia and carbon dioxide and to result in an ammonia fraction and a nutrient salt fraction, and separating the nutrient salt fraction into a fertiliser concentrate fraction and a water fraction, e.g. using reverse osmosis. The end products of the method are clean water, ammonia concentrate, fertiliser concentrate containing salts of P and K, compost and high-quality biogas with a high methane content.

Automatic cleaning system for a reverse osmosis unit in a high purity water treatment system

Abstract: A self contained water purification process system uses a self cleaning, self sanitizing reverse osmosis unit for reliably producing purified water, storing the water, and distributing it to a central supply piping system while maintaining the integrity of the purified water. Make-up water is prepared for reverse osmosis purification by means of staged conventional filtration and chlorine removal. The prepared make-up water is then fed into one or more reverse osmosis modules by a pump at a high velocity and pressure. About 85 percent of the make-up water exits the module as purified water. All of the water not passing through the reverse osmosis membranes returns to the suction end of the pump where it blends with incoming make-up water except for a small portion that is discharged to a waste drain. The high velocity flow maintains a shear effect within the modules to prevent a sediment deposition and biofilm from occurring on the membranes and increases the efficiency of water usage. During an automatic unattended cleaning sanitizing cycle, the recycled water is diverted through an injector which draws cleaning chemical into the stream.

Method for producing high purity water using triple pass reverse osmosis (TPRO)

Abstract: A method for producing high purity product water using a three pass reverse osmosis system.

Treatment of water

Abstract: A desalinator is disclosed for removing dissolved solids from sea water or brackish water. The desalinator (10) comprising a casing (12) into which a pump (14) driven by a motor (16) pumps sea water or brackish water under pressure. A desalination cartridge (76) within the casing (12) includes semi-permeable material which acts as a reverse osmosis membrane and through which permeate is forced to separate it from the sea water or brackish water. The solids dissolved in the brackish water or sea water are retained in the salt retention passages of the cartridge (76). Three electrical coils (94, 96 and 98) encircle the cartridge (76) and are embedded in the walls of the casing (12). The coils are supplied with current from a supply (112) which is preferably a 50 Hertz, 380 Volt three phase supply. The coils are also connected by lines (108) to an adjustable frequency AC drive (110) which is in turn connected to the motor (16). The coils (94, 96 and 98) impose a magnetic field on the sea water or brackish water in the salt retention passages which enhances the rate at which water permeates through the reverse osmosis membrane and also inhibits fouling. The coils (94, 96 and 98) additionally act as chockes for the motor (16).

Method and apparatus for reducing scaling in electrodeionization systems and for improving efficiency thereof

Abstract: A method and apparatus for inhibiting scaling in an electrodeionization system or in a combined reverse osmosis/electrodeionization system for water treatment and, more particularly, for increasing tolerance to hardness in the feed water to an electrodeionization unit to inhibit precipitation of metal cations contained in the feed water and for increasing efficiency of the electrodeionization system. Water to be purified is passed through a electrodeionization unit in which a concentrate stream recycling through concentrating compartments and anode and cathode compartments contains effective amounts of an antiscalant to inhibit precipitation of scale. One or more preliminary reverse osmosis units in series with the electrodeionization unit preferably receives a portion of the antiscalants in the concentrate stream. The antiscalant in the water fed to the reverse osmosis unit can be supplemented and adjusted. Electrolyte can be provided to the concentrate stream of the electrodeionization unit from products of the reverse osmosis.