Provided is a method for producing purified acetic acid from a mixed solution containing acetic acid, an organic solvent, and water in an energy-efficient manner. The method, which is for producing purified acetic acid from a mixed solution containing acetic acid, an organic solvent, and water, includes: a distillation step in which the mixed solution is distilled and separated into a purified liquid rich in acetic acid and a separated liquid rich in an organic solvent; and a membrane separation step in which the water is separated from the purified liquid by a separation membrane. The purified liquid has a water concentration of 4 wt.% or less.

In a process for treating wastewater from a combined gasification and Fischer-Tropsch (F-T) process, feedstock derived from Municipal Solid Waste or the like is gasified in a reactor (R) and treated in a cleanup unit (C) which generates a first wastewater stream (1st WWT STREAM) containing salts and inorganic pollutants. The first wastewater stream is treated in a treatment unit (T1) to remove inorganic pollutants derived from the syngas The treatment comprises a) degassing, and subsequently b) neutralising the first wastewater stream before treatment in a Dissolved Air Flotation unit (72c) and filtering in a moving sand bed or similar (72d) to remove solids, and a stripping process to remove ammonia. A second wastewater stream (2.sup.nd WWT Stream) containing organic pollutants but being low in salts arises from the F-T process and is treated separately to allow recycling within the F-T process.

A method for treating wastewater and an activator for treating wastewater that maximizes the utilization of microorganisms such as Bacillus bacteria in an activated sludge treatment of wastewater while minimizing treatment cost. In the method for treating wastewater, wastewater including organic matter is introduced into a treatment tank and the wastewater is subjected to an activated sludge treatment by microorganisms in the treatment tank, wherein an activator containing a component for activating the microorganisms is added to the wastewater to be subjected to the activated sludge treatment in the treatment tank; and at least 50% (by quantity) of the entirety of the activator has a particle size of less than 10 pm. Also provided is an activator therefor. The microorganisms preferably include Bacillus bacteria.

The present invention provides a flocculant for catalytic decomposition of flue gas desulfurization wastewater treatment. The flocculant includes polyacrylamide, inorganic polymer, and an inorganic compound with low molecular weight. In the condition of using proper components, the flocculant has significant wastewater treatment performance.

A method for treating a urea aqueous solution includes a first stripping step of steam stripping an aqueous solution containing urea, ammonia and carbon dioxide at 0.2 to 0.6 MPaA in a first stripper to separate ammonia and carbon dioxide from this aqueous solution into a gas phase; a hydrolysis step of hydrolyzing urea in the solution obtained from the first stripping step at an LHSV of 10 to 20 h.sup.−1, at 1.1 to 3.1 MPaA and 180 to 230° C. in a catalytic hydrolyzer; and a second stripping step of steam stripping a liquid obtained in the hydrolysis step in a second stripper to separate ammonia and carbon dioxide from this liquid into a gas phase. The residual urea concentration can be reduced to 1 ppm or lower; the residual ammonia concentration can be decreased; LHSV can be increased; and an increase in apparatus size is minimized.

Water treatment compositions are provided that are effective for mitigating corrosion or fouling of surfaces in contact with aqueous systems. The water treatment compositions can include one or more azole compounds, one or more transition metals, and one or more dispersants, in addition to various other additives. The water treatment compositions can exclude phosphorus and still be effective. Methods for mitigating corrosion or fouling of a surface in an aqueous system are also provided.

A method and system for treating cyanide-containing fluids, in particular cyanide-containing waste water, wherein cyanide-containing fluid is subject to a pretreatment in a pretreatment zone, in which at least one predetermined pH value and a predetermined temperature is set, wherein a base fluid is formed with the pretreatment. Base fluid is reacted at least with an oxidation means in at least one reaction reactor, whereby an oxidation reaction of the cyanide is initiated. Fluid from the reaction reactor is transferred as intermediate fluid into at least one process reactor, in which conditions exist in which the oxidation reaction of the cyanide initiated in the reaction reactor can take place, wherein a process fluid is formed. A continuous flow of fluid is maintained at least periodically, wherein the base fluid is transferred continuously from the pretreatment zone into the reaction reactor, intermediate fluid is transferred continuously from the reaction reactor into the process reactor, and process fluid is removed continuously from the process reactor.

The invention relates to a method of circular use of waste brine produced in the manufacture process of MDI, comprising the following steps: (1) the waste brine produced in the manufacture process of MDI is subjected to a high-gravity extraction and then to a column extraction, wherein said waste brine contains aniline, diaminodiphenylmethane and polyamine; (2) the waste brine from step (1) is transmitted to a stripping tower for steam stripping; (3) the waste brine from the stripping tower of step (2) and a chemical oxidant are transmitted to an oxidation reactor to which air is blown for aeration; (4) the waste brine after the treatment of step (3) is transmitted to an absorption tower for absorption. The invention makes the salt water have TOC of less than 8 ppm and TN of less than 2.5 ppm and achieves regeneration of resources in the waste brine such as sodium chloride and water and the like for circular use.

A process for the treatment of waste water, spent air, and hydrocarbon containing liquid and gaseous streams in the cumene/phenol complex is described. Various effluent streams are combined in appropriate collection vessels, including a spent air knockout drum, a hydrocarbon buffer vessel, a fuel gas knockout drum, a phenolic water vessel, and a non-phenolic water vessel. Streams from these vessels are sent to a thermal oxidation system.

Method for isolating carboxylic acid from an aqueous metal carboxylate-containing side stream of an organic peroxide production process, involving the protonation of the carboxylate, separation of liquid and organic phases, and the removal of residual peroxides.