| 摘要 |
Systems and methods for clarifying liquids, especially water, of the two stage upflow/downflow type are improved by the use in the first, upflow stage of particulate filter media consisting of solid particles with a density of between 3.5 and 4.4 and a size between 1.5 and 4 mm. and, preferably, in the second, downflow stage particulate filter media consisting of solid particles having densities of between 1.5 and 24.0 and sizes of between 0.3 and 1.5 mm.
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