Kurita Water Industries Ltd.

Shigeki Fujishima

Nozomu Ikuno

Motoyuki Yoda

Nobukazu Arai

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

A biological treatment method and device for organic wastewater, whereby the amount of minute organisms which reduce the amount of excess sludge and held within an activated sludge tank can be stabilized so that the treatment can be stabilized, are provided. Substrates for growing dispersed bacteria and/or dispersed bacteria are supplied to a sludge treatment tankwhich reduces the sludge by the minute organisms, so that the minute organisms grow stably and reduce the sludge. Specifically, a first and a second biological treatment step are conducted respectively in a first activated sludge tankand a second biological treatment tank. The sludge included in effluent which flows from the biological steps is separated in a sedimentation tank. The generated sludge obtained is supplied to the sludge treatment tank. The water to be treated which is bypassed via a bypass pathis introduced to a sludge treatment tankas substrates to be assimilated by bacteria so that dispersed bacteria are made to grow in the sludge treatment tankand the minute organisms are held stably in the sludge treatment tankto promote the reduction of sludge.

Method for biological disposal of organic wastewater and biological disposal apparatus

A multistage activated sludge process involving a predation effect caused by microorganisms realizes further improvement in treatment efficiency and further decrease in the amount of excess sludge generated while a stable quality of the treated water is maintained. This process includes a first biological treatment process for treating BOD in organic wastewater at a high load to convert the BOD to dispersed bacteria, and a second biological treatment process for forming the converted dispersed bacteria into a floc and allowing microorganisms to coexist. The second biological treatment process is performed under a condition of pH 5 to 6. Alternatively, an excess sludge treatment process for decomposing at least a part of sludge in the second biological treatment process and/or sludge obtained by performing solid-liquid separation of sludge in the second biological treatment process under aerobic conditions, and returning the treated sludge to the first biological treatment process and/or the second biological treatment process is performed under a condition of pH 5 to 6.

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Tokyo, Japan

Shigeki Fujishima