Abstract: 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 means 1 and 2 having 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.

Abstract: 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.

Abstract: 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 Cl2.

Abstract: There are provided a method and an apparatus for treating organic matter-containing water, the method and apparatus being capable of inhibiting the multiplication of microorganisms in an activated carbon column and a reverse osmosis membrane separator and performing stable treatment over long periods of time in a process including active carbon treatment and subsequent RO membrane separation treatment with an ultrapure water production system for use in electronic device manufacturing plants.