Abstract: 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.

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: 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.

Abstract: In a water treatment method, raw water supplied from a water supply reservoir for reserving the raw water is biologically treated by a biological treatment means before being supplied to a primary pure water apparatus. Thereafter, urea or a urea derivative and/or an ammoniacal nitrogen source (NH3—N) are added before the biological treatment means. In such a treatment flow, it is preferred that a reduction treatment means is provided after the biological treatment means and before the primary pure water apparatus. According to the water treatment method, the TOC, in particular urea, in the raw water can highly be decomposed.

Abstract: A urea removal capability is increased in a water treatment method of introducing raw water containing organic substances, specially, urea to a reaction tank, adding water-soluble bromide salt and an oxidizing agent to perform an oxidation treatment on the urea, subsequently, performing a bio-treatment by a bio-treatment means. According to the water treatment method, TOC, particularly, urea in the raw water can be highly decomposed.

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.