Kurita Water Industries Ltd.

Nozomu Ikuno

Nobukazu Arai

Shigeki Fujishima

Mamoru Iwasaki

Motomu Koizumi

Provided is a method for controlling a pH to a neutral range (pH 6 to 8) by adding an alkali or an acid to decarbonated water, including controlling the amount of the alkali or the acid added using an electrical conductivity meter. The decarbonated water is, for example, water obtained by decarbonating industrial water or groundwater so that the concentration of carbonic acid is 10 ppm or less. The method may further have a step of producing pure water by RO treatment of the decarbonated water with a pH adjusted to 6 to 8 by the pH control.

Method for controlling pH by electrical conductivity

Provided is a method for treating water containing a low-molecular-weight organic substance which enables the low-molecular-weight organic substance to be removed with certainty at a sufficient level without subjecting the water to a biological treatment. A method for treating water containing a low-molecular-weight organic substance, the method comprising passing raw water to a high-pressure reverse-osmosis-membrane separation device, the raw water containing a low-molecular-weight organic substance having a molecular weight of 200 or less at a concentration of 0.5 mgC/L or more, wherein an amount of brine discharged from a reverse-osmosis-membrane module () disposed at an end of a final stage of the high-pressure reverse-osmosis-membrane separation device is 2.1 m/(m&#xb7;D) or more.

Method for treating water containing low-molecular-weight organic substance

The present invention provides an apparatus and method for producing ultrapure water of extremely high purity that sufficiently meets the requirement for its quality at low production cost with reduced footprint. The apparatus for producing ultrapure water includes a pretreatment system, a primary water purification system, and a subsystem, wherein the primary water purification system includes a high-pressure reverse osmotic membrane separation unit, a degassing unit, an ultraviolet oxidation unit, and an ion-exchange unit in this order.

Ultrapure water production apparatus and ultrapure water production method

Disclosed is a treatment apparatus capable of inhibiting growth of microorganisms and carrying out long-term stable treatment in an activated carbon tower and a reverse osmosis membrane separation device during processes including activated carbon treatment and RO membrane separation treatment of a later step in a system for manufacturing ultrapure water used in an electronic device factory. A method for treating organic-matter-containing water includes: the slime-controlling-agent-adding step of adding a slime-controlling agent to organic-matter-containing water; the activated-carbon-treating step of treating with activated carbon the organic-matter-containing water having undergone the slime-controlling-agent-adding step; and the reverse-osmosis-membrane-separation step of passing the organic-matter-containing water having undergone the activated-carbon-treating step through means for reverse osmosis membrane separation, wherein the slime-controlling agent uses a combined chlorine agent produced from a chlorine-based oxidizer and a sulfamic acid compound.

Method for treating organic-matter-containing water

In an ultrapure water producing method, a pre-treatment system treats raw water supplied from a raw water storage tank. A heat exchanger adjusts the treated water to a predetermined temperature before the water is supplied to a first bio-treatment means which is further connected to a second bio-treatment means. The second bio-treatment means is connected to a microbial body separation apparatus and, after treatments are performed in those apparatuses, the result is supplied as treated water to a primary pure water apparatus. Before the second bio-treatment means, a second supply mechanism is provided for adding a nitride source as a nutrient source and oxidizing agent (bactericidal agent). According to the ultrapure water producing method, urea in raw water can be removed to a high degree.

Ultrapure water producing method and apparatus

Ultrapure water of high purity having extremely low TOC concentration is produced by efficiently degrading urea in raw water by biological activated carbon treatment even when the raw water contains ammonium nitrogen. The ultrapure water production method, where raw water is treated in a primary pure water system, and then the resulting water is treated in a subsystem, contains a step of treating pretreated water with chlorine based oxidizer added by a biological treatment means installed upstream to the subsystem. Chlorine based oxidizer is added so that the chlorine based oxidizer concentration is 5 times or more than the ammonium nitrogen concentration of water treated in the biological treatment means in terms of Cl.

Ultrapure water production method and apparatus therefor

A water treatment method and a method for producing ultrapure water are provided in which urea in raw water is sufficiently decomposed, and an organism (bacterial cells) in biological treatment is prevented from flowing downstream. In a water treatment method for performing biological treatment of raw water containing urea, a carbon source is added to the raw water, and the raw water is then supplied to biological treatment meansandhaving a fixed bed formed of an organism-supporting carrier to perform the biological treatment. The biological treatment after the addition of the carbon source to the raw water improves the efficiency of decomposition and removal of urea. The biological treatment means using a fixed bed formed of an organism-supporting carrier decreases the number of bacterial cells flowing downstream.

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Tokyo, Japan

Nozomu Ikuno