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An experimental study on the impact of bioflocculation on activated sludge separation techniques

机译：生物絮凝对活性污泥分离技术影响的实验研究

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Membrane bioreactors have become a well-established alternative for conventional activated sludge systems with a filtration instead of a sedimentation step to separate the sludge from the purified water. Both separation processes, however, depend on good bioflocculation for their performance. Small activated sludge constituents are known to be detrimental in activated sludge filtration, while poor settling can often be attributed to improper floc formation. Therefore, the aim of this paper is to further unravel the relationship between bioflocculation and activated sludge separation processes. To this end, synthetic influents with different mono-over-polyvalent (M/P) cationic compositions are used to create activated sludges with different morphologies and bioflocculation states during a 178 days experiment. The activated sludges were characterized by microscopic image analysis, relative hydrophobicity, extracellular polymeric substances, and were subjected to sedimentation, dead-end and submerged crossflow filtration tests. The deflocculating effect of a high M/P ratio is affirmed, inducing the release of colloidal material that caused severe fouling. Sludge flocs became empty and did not settle well. In the low M/P reactor, overall a better separation performance was observed but a non-expected filamentous bulking episode caused bad settleability and bad crossflow filterability, while dead-end filterability was good since a porous, well structured fouling layer was formed. Hence, it is concluded that dead-end filtration tests cannot asses sludge filterability in MBRs and that big activated flocs cannot contribute to the cake layer and cannot ensure its porosity in this way. Hydrophobicity was generally higher in the low M/P reactor but this might be attributed to an abundance of filaments during part of the testing period. No conclusive information could be extracted regarding the role of EPS, thus the use of EPS as a fouling or bioflocculation indicator is (again) questioned. (C) 2014 Elsevier B.V. All rights reserved.
机译：膜生物反应器已经成为传统活性污泥系统的公认替代品，它具有过滤功能而不是沉淀步骤，可将污泥与纯净水分离。然而，两种分离方法的性能均取决于良好的生物絮凝。众所周知，小的活性污泥成分对活性污泥的过滤是有害的，而沉降不良通常归因于絮凝物形成不当。因此，本文的目的是进一步阐明生物絮凝与活性污泥分离过程之间的关系。为此，在178天的实验中，使用了具有不同的单价多价（M / P）阳离子组成的合成进水来产生具有不同形态和生物絮凝状态的活性污泥。活性污泥通过显微镜图像分析，相对疏水性，细胞外聚合物质进行表征，并进行沉淀，死角和浸没错流过滤测试。确认了高M / P比的抗絮凝作用，导致胶体物质的释放，导致严重的结垢。污泥絮凝物变空并且沉降不好。在低M / P反应器中，总体上观察到更好的分离性能，但未预期的丝状膨胀事件导致差的沉降性和差的错流过滤性，而死端过滤性则好，因为形成了多孔的结构良好的结垢层。因此，得出的结论是，死端过滤测试无法评估MBR中污泥的可过滤性，并且大的活性絮凝物无法形成滤饼层，因此无法确保其孔隙率。在低M / P反应器中，疏水性通常较高，但这可能是由于在部分测试期间内长丝的存在所致。无法获得关于EPS的作用的结论性信息，因此再次质疑EPS作为结垢或生物絮凝指标的用途。 （C）2014 Elsevier B.V.保留所有权利。

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