Anaerobic processes in activated sludge

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• 作者：de Beer ; Dirk ; Schramm ; Andreas ; Santegoeds ; Cecilia M. ; Nielsen ; Helle K.
• 关键词：Activated sludge ; micro-environment ; oxic ; anoxic ; microsensor ; sulfate reduction ; denitrification ; confocal microscopy
• 刊名：Water Science and Technology
• 出版年：1998
• 期刊代码：74_02731223
• 类别：env
• 出版时间：1998
• 卷：37
• 期：4-5
• 页码：605-608
• 文件大小：219 K

摘要

We found anoxic zones in aerated activated sludge flocs, and demonstrated denitrification under normal operating conditions. Sulfate reduction was not found. Micro-environments and microbial conversions in flocs from bulking and non-bulking activated sludge were determined with microsensors for H₂S, O₂, NO_2⁻ and NO_3⁻. Denitrification and sulfate reduction rates were mmeasured with ¹⁵N- and ³⁵S-tracer techniques. We showed that under normal reactor conditions (ca. 20%air saturation) anoxic zones develop within flocs allowing denitrification. The denitrification rates amounted to 40%of the rates under anoxic conditions. At 100%air saturation no anoxic zones were found and no denitrification occurred. However, in flocs from bulking sludge (at 20%air saturation) anoxic zones were absent and denitrification did not occur. In bulking sludge only at total anoxia was denitrification found. Confocal microscopy showed that flocs from bulking sludge were much looser than those from non-bulking sludge. The absence of anoxic zones and of denitrification was attributed to the open floc structure, allowing advective oxygen transport.