A process for treatment of water via membrane separation to remove hardness and non-hydroxide alkalinity by simultaneous removal in a weak acid cation exchange resin. The process includes ionization of sparingly ionizable components, such as silica, by adjusting the pH up to about 10.5 or higher. Their separation by the membrane is significantly increased. The passage of boron, silica and TOC is reduced by a factor of ten or more. Recovery of 90 % or higher is achievable with most brackish feedwaters, while substantial reduction in cleaning frequency is simultaneously achieved. The apparatus used for the water treatment process includes reverse osmosis membrane(s) (30), mixed bed ion exchange unit (44, 46), micron filter (48), ultraviolet sterilization unit (49), decarbonation unit (20), and electrodeionization unit (150).

Method and apparatus for high efficiency reverse osmosis operation

Processes and apparatus are disclosed for producing clear reverse osmosis retentates having silica concentrations which are substantially supersaturated in silica from feedwaters having silica concentrations, without substantial formation of alkali-soluble scale having substantial silica content in the associated reverse osmosis apparatus, by adjusting the pH of such feedwaters to an acidic pH range prior to reverse osmosis in accordance with this invention. Also disclosed are related processes and apparatus for periodically removing minor amounts of alkali-soluble scale having substantial silica content from the apparatus.

High recovery reverse osmosis process and apparatus

A process for treatment of water via membrane separation equipment. A feedwater is maintained or adjusted to a pH of 4.3 or lower, and fed to a membrane separation system. In this manner, species such as TOC become more ionized, and (a) their rejection by the membrane separation process is significantly increased, and (b) their solubility in the reject stream from the membrane process is significantly increased. Passage TOC through the membrane is significantly reduced. A recovery ratio of eighty percent (80%) or higher is achievable with most feedwaters, while simultaneously achieving a substantial reduction in cleaning frequency of the membrane separation equipment. The method is particularly useful for the preparation of high purity water.

Method and apparatus for treatment of feedwaters by membrane separation under acidic conditions

The invention relates to systems and methods of treating water by directing the water to a first reverse osmosis (RO) membrane; separating the water using the first RO membrane; adding a chelating agent to first permeate and/or raising the pH of the first permeate to between about 5.5 and 7.5 before a second RO membrane; and separating the first permeate into a second permeate and a second concentrate using the second RO membrane, thereby separating constituents from the water.

Treating acidic water

PROBLEM TO BE SOLVED: To provide a pure water production system where pure water stored in a pure water tank is constantly maintained with a desired high purity, and the pure water having high purity can be always fed to an external apparatus. SOLUTION: The on/off control of a pure water device is performed (S1). The present water position is detected by a water position sensor 12 (S2), whether a timer counts a prescribed time or not is judged, and, when the prescribed time is passed, whether water position variation is caused or not is judged (S3→S4). Then, in the case water position variation is caused, the on/off control of the pure water device is performed (S4→S1), on the other hand, in the case water position variation is not caused, when the water position of a treatment water tank is less than the stop water position of a circulation pump, the pure water device is forcibly driven, and on the other hand, when the water position is more than the stop water position of the circulation pump, the circulation pump is driven, and at the point of time of lowering to the stop water position, the circulation pump is stopped, the pure water device is forcibly driven, and thereafter, the on/off control of the pure water device is performed, and the above treatments are repeated. COPYRIGHT: (C)2010,JPO&INPIT

Pure water production system

PURPOSE: To obtain highly desalted water containing no scale and sludge, by performing desalting by reverse osmosis treatment in a first stage wherein an acid is added to water to remove the divalent ion therein and a second stage wherein an alkali agent is added to water to remove silica. CONSTITUTION: Raw water 1 containing silica at high concn. is pressurized by a pressure pump 5 to raise the pressure thereof to reverse osmosis pressure and sent to a reverse osmosis apparatus 6 to be subjected to first stage reverse osmosis treatment. At this time, an acid is injected in raw water in order to prevent scaling and the pH of raw water at the inlet of the reverse osmosis apparatus 6 is adjusted to weak acidity. The transmitted water 9 from which the hardness components in water such as calcium and magnesium are removed at a high ratio in the first stage is contacted with air in a decarbonator 10 to remove carbon dioxide. An alkali agent is added to the treated water after degassing from a storage tank 10 to raise the pH of the treated water to make it possible to raise silica solubility to a large extent and silica is removed in the reverse osmosis apparatus 19 at a second stage. COPYRIGHT: (C)1987,JPO&Japio

Reverse osmosis treatment of water containing silica at high concentration

PURPOSE:To solve complexity of washing by subjecting brine to low-pressure reverse osmosis treatment to perform preliminary desalting and thereafter subjecting permeated water to electrodialysis treatment to perform final desalting. CONSTITUTION:Raw brine 3 is sent to a filter 6 while introducing a flocculating agent or the like and filtered. Thereafter acid is introduced with an acid introducing pump 10 to regulate pH. Filtered water subjected to pH regulation is passed through a micron-filter 11 and pressurized with a pressurizing pump 12 and sent to a reverse osmosis apparatus 8 and treated. Permeated water 13 is sent to a circulation tank 18 from a permeated water tank 15 with a permeated water pump 17 and sent to an electrodialysis apparatus 14 with a circulation pump 19 and subjected to electrodialysis treatment, circulated and desalted to a level necessary for application and made to desalted water 20. Thereby desalted water can be obtained at high recovery.

Method for desalting brine

PURPOSE:To remove a dissolved carbon dioxide in water at a high rate by dividing a reverse osmosis device to two stages, permitting the permeation of the carbon dioxide in a 1st stage, converting the dissolved carbon dioxide to anion form by pH adjustment in a 2nd stage and removing said gas by executing a reverse osmosis treatment. CONSTITUTION:After raw water 1 contg. the free carbon dioxide is subjected to reverse osmosis, said water is subjected to an ion exchange treatment by which pure water is produced. The treatment is executed by using the reverse osmosis device 6 which removes the hardness component in the raw water at a high rate for the 1st stage of said reverse osmosis treatment. The pH of the permeated water is adjusted to an alkali side by adding an alkali agent to waid water and if necessary, an extremely slight amt. of a scale preventive agent (e.g., polyphosphate) is added thereto. The treatment to remove the carbon dioxide component converted to bicarbonate ions and carbonate ions in the above-mentioned manner is executed by using the 2nd stage of the reverse osmosis device 20. As a result, the dissolved carbon dioxide in the water is removed at a high rate prior to the execution of the ion exchange treatment.

Mitsukami Yoshimichi

Papers

Reverse osmosis treatment of water containing silica at high concentration

Method for desalting brine

Method for removing dissolved carbon dioxide in pure water producing apparatus