| 摘要 |
The invention relates to a process for the biological purification of waste water in an activation plant having two stages 1, 20, in which an activation tank 2, 21 and a settling tank 3, 22 with sludge return 4, 23 into the particular activation tank 2, 21 are assigned to the two stages 1, 20 and in which the outlet 7 of the settling tank 3 of the first stage 1 is connected to the activation tank 21 of the second stage 20. For as complete as possible an elimination of both readily and poorly degradable impurities, the oxygen supply of the activation tank 2 of the first stage 1 is kept below the respiratory activity of the microorganisms present and the oxygen supply of the activation tank 21 of the second stage 20 is set to at least correspond to the respiratory activity of the microorganisms present. In spite of the low oxygen demand in the activation tank 2 of the first stage 1, the treatment gas fed to the activation tank 2 via a line 8 is a gas containing more oxygen than air. The exhaust gas produced is withdrawn via an exhaust gas line 13. <IMAGE>
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