| 摘要 |
<p>In an installation for the biological purification of domestic and industrial sewage using activated sludge, the effluent flows through a pre-clarifying stage to a secondary clarification tank with sludge separation, by way of a number of extensive aerating stages of such dimensions that the water flows through under pressure. These aerating stages are divided into two groups, the water flowing through being subjected to a higher localised gas pressure in the first than in the second. The gas pressure is infinitely variable and if gases with a similar oxygen content are used in both stages, the oxygen part pressure is increased in the first stage by intensifying the gas pressure, whereas, if the oxygen content of the gases for the two stages is different, the oxygen part pressure in the first stage is increased by raising the oxygen content of the gas supplied. Whilst having the smallest dimensions possible, the plant can be operated in the most economical manner according to the nature of the sewage being processed. In large installations, the reduction in pressure between the two stages can be effected by decompression turbines, so as to recover some of the energy in the system.</p> |
