Abstract: Water to be purified is passed through a reverse osmosis step to produce a pure water stream and a waste water stream. The waste water is directed to a deionization step to produce purified deionized water which is recycled to the reverse osmosis step. The process directs far less water to waste as compared to conventional reverse osmosis processes. The process also produces water of higher organic and inorganic purity than can be obtained by either reverse osmosis or deionization alone.

Abstract: Ultrapure water containing less than 10 ppt total ions, other than hydrogen ion and hydroxide ion is produced by passing deionized water through a system comprising an ultrafiltration step, an oxidizing step where water is exposed to ultraviolet light and ion exchange step. The treated water is recirculated through the oxidizing step and the ion exchange step. Product water from the system can be recovered on a continuous basis so long as the ratio of volume of water circulated within the system to volume of water drawn from the system is at least 10 and preferably at least 20.

Abstract: A method for treating a pulp and paper manufacturing stream to remove colorants therefrom comprises: contacting the stream with a first adsorbent comprising the calcined product of a compound having the formula: A.sub.w B.sub.x (OH).sub.y C.sub.z.nH.sub.2 O, wherein A represents a divalent metal cation; B a trivalent metal cation; C a mono- to tetravalent anion; and w, x, y, z and n satisfying the following: 0<z.ltoreq.x.ltoreq.4.ltoreq.w.ltoreq.1/2y and 12.gtoreq.n.gtoreq.1/2(w-x); then contacting the stream with a second adsorbent consisting essentially of activated carbon. On a preferred basis, the first contacting adsorbent is a hydrotalcite derivative made by reacting activated magnesia with an aqueous solution of aluminate, carbonate, and hydroxyl anions before calcining at one or more temperatures between about 400.degree.-650.degree. C.

Abstract: A method and apparatus predict the organic carbon content of water discharged from a water purification system. Water is directed from a water source across, for example, a source of ultraviolet light of the water purification system under substantially steady-state conditions. A reference mode is established, whereby a reference-mode resistivity change is determined. A purification-mode is then established, whereby a purification mode resistivity change is measured. The reference-mode resistivity change and the purification-mode resistivity change are then combined to obtain a purified value which is associated with the carbon content of water discharged from the water purification system, thereby predicting the carbon content of water discharged from the water purification system.

Abstract: Water to be purified and degassed is passed through a reverse osmosis step which a pure water stream and a high pressure waste water stream are produced. The high pressure waste water is passed through an eductor to produce a vacuum. The pure water stream is passed into a first volume of a degassifier and the vacuum is directed to a second volume of the degassifier. The first and second volume of the degassifier are separated by a hydrophobic membrane.

Abstract: A dry flocculant powder comprises an inorganic substrate consisting essentially of metal oxide/hydroxide particles having an average particle size of less than about 30 microns, said substrate having a cationic or anionic polyelectrolyte coated onto its outer surface, preferably under other than high shear conditions. A method for coating or adhering polyelectrolytes to the outermost surface of inorganic particles comprises dispersing a polyelectrolyte in a substantially non-aqueous solvent, preferably having a low boiling point and a low to intermediate polarity relative to the polyelectrolyte; adding the inorganic particles to the solvent to form a slurry; mixing the slurry under low to moderate shear conditions; and removing excess solvent from the slurry. There is also disclosed a method for removing clay, clay-like materials, humic acids, yeast, biological cells and/or other cell debris from an aqueous stream through contact with the aforementioned dry flocculant powder.

Abstract: A method for treating caustic solutions to remove colorants, including iron, therefrom comprises: contacting the solution with a substance comprising a calcined product of a compound having the formula: A.sub.w B.sub.x (OH).sub.y C.sub.z.nH.sub.2 O, wherein A represents a divalent metal cation; B a trivalent metal cation; C a mono- to tetravalent anion; and w, x, y, z and n satisfying the following: 0<z.ltoreq.x.ltoreq.4.ltoreq.w.ltoreq.1/2y and 12.gtoreq.n.gtoreq.1/2(w-x). On a preferred basis, the contacted substance is a hydrotalcite derivative made by reacting activated magnesia with an aqueous solution of aluminate, carbonate, and hydroxyl anions before calcining at one or more temperatures between about 400.degree.-650.degree. C. There is further disclosed a method for producing an aluminum hydroxide having improved whiteness according to the invention.

Abstract: A method for reducing the amount of anionic metal-ligand complex in a solution comprises: (a) contacting the solution with a substance selected from: a compound having the formula: A.sub.w B.sub.x (OH).sub.y C.sub.z.nH.sub.2 O, wherein A represents a divalent metal cation, B represents a trivalent metal cation, C represents a mono- to tetravalent anion, and w, x, y, z and n satisfy the following: 0.ltoreq. z.ltoreq.x.ltoreq.4.ltoreq.w.ltoreq.1/2y and 12.gtoreq.n.gtoreq.1/2(w-x); a calcined product of said compound and mixtures thereof; and (b) separating the substance from the solution. A method for removing substantially all metal-cyanide, -thiocyanate, -thiosulfate, -citrate and/or -EDTA complex from a solution containing one or more of said complexes is also disclosed.

Abstract: A method is disclosed for reducing the amount of a first contaminant and second contaminant in a solution to environmentally safe levels, said solution having a substantially greater amount of the first contaminant than the second contaminant. The method comprises: contacting the solution with an activated or calcined product of a compound having the formula A.sub.6 B.sub.2 (OH).sub.16 C.4H.sub.2 O, wherein A is a divalent metal cation, B is a trivalent metal cation and C is a mono- to tetravalent anion. The method further comprises separating the solution from the contacted product. The method is particularly useful for removing both selenium and sulfate, arsenic and sulfate, or arsenic and phosphate from a waste water stream. An unpredicted preference for selenium and arsenic, in the presence of other contaminants including sulfate and phosphate, was also shown herein.

Abstract: A method for reducing the amount of anionic metal-ligand complex in a solution comprises: (a) contacting the solution with a substance selected from: a compound having the formula: A.sub.w B.sub.x (OH).sub.y C.sub.z .multidot.nH.sub.2 O, wherein A represents a divalent metal cation, B represents a trivalent metal cation, C represents a mono- to tetravalent anion, and w, x, y, z and n satisfy the following: 0.ltoreq.z.ltoreq.x.ltoreq.4.ltoreq.w.ltoreq.1/2y and 12.gtoreq.n.gtoreq.3/2x; a calcined product of said compound and mixtures thereof; and (b) separating the substance from the solution. A method for removing substantially all metal-cyanide, -thiocyanate, -thiosulfate, -citrate and/or -EDTA complex from a solution containing one or more of said complexes is also disclosed. The latter method comprises contacting the solution with a sufficient amount of substance consisting essentially of a compound selected from: hydrotalcite, calcined hydrotalcite and mixtures thereof.