| 摘要 |
The present invention relates to a technology which can efficiently concentrate a suspension liquid which needs to be concentrated in sewage treatment plants or various waste water treatment plants, particularly sludge or the like which contains a large amount of odor components which will adversely be decayed and is hard to concentrate. The present invention can prevent odor substances from being produced in a concentration process, and can remarkably reduce the amount of odor components, carbonic acid, and the like contained in concentrated sludge or a lower separated liquid. Specifically, in a process of concentrating or dewatering residual evaporated substances in a liquid, when sludge is held under a reduced pressure of 5 to 70 kPa for less than 15 minutes, a portion of gas components dissolved in the liquid is changed into gaseous phase, and activation of microorganisms in the liquid is restricted. After a decompressing process is performed under the reduced pressure, the liquid is introduced into a gravity concentration tank for gravity concentration, or the decompressed liquid or the gravity-concentrated sludge is introduced into a flocculation reaction tank for flocculation, and is then dewatered by a dewatering device. <IMAGE>
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