| 摘要 |
Process and apparatus for thickening or dewatering treated sludge in one or more thickening tanks includes the addition of nitrate ions to treated sludge as a mechanism for generating microscopic bubbles of nitrogen gas which adhere to, or are trapped by, sludge floc particles, causing a reduction in density of the particles which, in turn, causes the particles to float to the top of the thickening tank. The process separates the sludge into an upper thickened layer and a lower free water, or subnate, layer. Subnate is removed from the tank through a plurality of outlets arranged at different depths within the tank. The subnate outlets are shut off sequentially, from the highest to the lowest, as the level in the tank drops. Thereafer, the thickened sludge is removed from the bottom of the tank and pumped to a sludge disposal location. A portion of the thickened sludge may be recirculated to insure flow uniformity.
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