Importance

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Abstract

Provided is a biological treatment method and an apparatus that allow organic wastewater from a manufacturing process of electronic devices to be neutralized efficiently during its biological treatment with a less neutralizer in contrast to excessive use thereof in the conventional biological treatment and thereby make it possible to reduce an amount of an inorganic coagulant used in the downstream coagulation step and to reduce salt loads in RO membrane separation and ion exchange treatment. Wastewater from a process of manufacturing electronic devices is passed sequentially through two or more biological treatment tanks that include at least two aerobic biological treatment tanks including the final-stage aerobic biological treatment tank while adding a neutralizer to the biological treatment tank or tanks except the final-stage biological treatment tank so that an M-alkalinity of the liquid in the final-stage biological treatment tank is maintained at not more than 50 mg/L as CaCO₃.

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First Claim