Vacuum treatment of activated sludge results in sludge degassing. The aim of the study was to determine what happens with sludge flocs and bacterial cells during degassing process and to answer why the sludge settles differently after degassing. Sludge settling properties before and after degassing of activated sludge were taken under consideration. It was found that during vacuum degassing 25–100% of flocs larger than 500 µm were broken up into smaller ones. The floc area decreased by 19 ± 19%. The most important changes in the floc parameters were floc area and fractal dimension. Floc fractal dimension increased by 5.8% in summertime and decreased by up to 5.4% in the rest of the seasons. About 20% of the bacterial cells were completely destroyed. The reduction in the floating sludge resulting from degassing was 83–100%. The effects of extracellular substance release, change of sludge volume index and strength of activated sludge were dependent on the season. The release of loosely bound extracellular polymers ranged from 20 to 78%, while release of tightly bound polymers was stable and of app. 85 mg organic carbon/g suspended solids. The research results show the potential of vacuum to disintegrate not only activated sludge flocs but also completely dead or weak cells. This causes the enrichment of active cells in the activated sludge. The shear stress originating from degassing causes release of extracellular polymeric substances that may serve not only as external carbon source but also as a flocculant for the renewal of vacuum-disintegrated flocs.

中文翻译：

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真空处理改变活性污泥的特性

真空处理活性污泥会导致污泥脱气。该研究的目的是确定脱气过程中污泥絮凝物和细菌细胞会发生什么，并回答为什么在脱气后污泥沉降不同的原因。考虑了活性污泥脱气前后的污泥沉降特性。结果发现，在真空脱气过程中，超过500 µm的絮凝物中有25–100％被分解成较小的絮凝物。絮状物面积减少了19±19％。絮状物参数最重要的变化是絮状物面积和分形维数。夏季，絮凝物的分形维数增加了5.8％，而在其余季节中下降了5.4％。约20％的细菌细胞被完全破坏。脱气后浮泥的减少量为83–100％。细胞外物质释放，污泥体积指数变化和活性污泥强度的影响取决于季节。松散结合的细胞外聚合物的释放范围为20％到78％，而松散结合的聚合物的释放是稳定的。85毫克有机碳/克悬浮固体。研究结果表明，真空不仅可以分解活性污泥絮凝物，还可以分解完全死亡或脆弱的细胞。这导致活性细胞富集在活性污泥中。源自脱气的剪切应力导致释放胞外聚合物质，这些物质不仅可以用作外部碳源，还可以用作絮凝剂，用于更新真空分解的絮凝物。松散结合的细胞外聚合物的释放范围为20％到78％，而松散结合的聚合物的释放是稳定的。85毫克有机碳/克悬浮固体。研究结果表明，真空不仅可以分解活性污泥絮凝物，还可以分解完全死亡或脆弱的细胞。这导致活性细胞富集在活性污泥中。源自脱气的剪切应力导致释放胞外聚合物质，这些物质不仅可以用作外部碳源，还可以用作絮凝剂，用于更新真空分解的絮凝物。松散结合的细胞外聚合物的释放范围为20％到78％，而松散结合的聚合物的释放是稳定的。85毫克有机碳/克悬浮固体。研究结果表明，真空不仅可以分解活性污泥絮凝物，还可以分解完全死亡或脆弱的细胞。这导致活性细胞富集在活性污泥中。源自脱气的剪切应力导致释放胞外聚合物质，这些物质不仅可以用作外部碳源，还可以用作絮凝剂，用于更新真空分解的絮凝物。研究结果表明，真空不仅可以分解活性污泥絮凝物，还可以完全分解死细胞或弱细胞。这导致活性细胞富集在活性污泥中。源自脱气的剪切应力导致释放胞外聚合物质，这些物质不仅可以用作外部碳源，还可以用作絮凝剂，用于更新真空分解的絮凝物。研究结果表明，真空不仅可以分解活性污泥絮凝物，还可以分解完全死亡或脆弱的细胞。这导致活性细胞富集在活性污泥中。源自脱气的剪切应力导致释放胞外聚合物质，这些物质不仅可以用作外部碳源，还可以用作絮凝剂，用于更新真空分解的絮凝物。