School of Environment, Guangdong Engineering Research Center of Water Treatment Processes and Materials, And Guangdong Key Laboratory of Environmental Pollution and Health, Jinan University, Guangzhou, 510632, China.
Department of Civil, Architectural and Environmental Engineering, Missouri University of Science and Technology, Rolla, MO, 65409, USA.
Water Res. 2019 Mar 15;151:134-143. doi: 10.1016/j.watres.2018.12.019. Epub 2018 Dec 20.
This study revealed that, Thiothrix eikelboomii, a well-known filamentous bacterium that causes sludge bulking, could also interfere oxygen transfer during wastewater treatment. The volumetric oxygen transfer coefficient (Ka) in filamentous-bulking sludge (FBS) was found to be 43% lower than that in floc-forming sludge (FFS) at similar biomass concentrations, partially because the filamentous bacteria had increased the sludge apparent viscosity. The Ka value for FBS, however, was still significantly lower than that for FFS even if both sludges had similar apparent viscosity. Numerous tiny and free-swimming filaments were observed to attach on the air bubble surface, presumably reducing the liquid film renewal and increasing the liquid film thickness. Moreover, the filaments were co-coated with extracellular polymeric substances of protein and polysaccharide, which could make them performing like "amphiphilic molecules" of surfactants to hinder oxygen transfer. Therefore, the particular surface property of filaments and their interaction with air bubbles could also impact oxygen transfer. Thiothrix eikelboomii was identified to be the responsible filamentous bacterium that lowered the Ka value, while other filamentous bacteria with short filaments did not interfere oxygen transfer. This study implies that controlling sludge bulking benefits not only sludge settling but also oxygen transfer.
本研究表明，一种已知的丝状菌——球衣菌，会导致污泥膨胀，它同样会干扰废水处理中的氧转移。在相似生物量浓度下，丝状膨胀污泥（FBS）的体积氧转移系数（Ka）比絮状形成污泥（FFS）低 43%，部分原因是丝状菌增加了污泥表观黏度。然而，即使 FBS 和 FFS 的表观黏度相似，FBS 的 Ka 值仍明显低于 FFS。大量微小的自由游动的丝状菌附着在气泡表面，这可能会减少液膜更新并增加液膜厚度。此外，丝状菌还与蛋白质和多糖组成的胞外聚合物共附着，这可能使它们表现得像表面活性剂的“两亲分子”，从而阻碍氧转移。因此，丝状菌的特殊表面性质及其与气泡的相互作用也会影响氧转移。确定球衣菌是降低 Ka 值的责任丝状菌，而其他具有短丝的丝状菌则不会干扰氧转移。本研究表明，控制污泥膨胀不仅有利于污泥沉降，还有利于氧转移。
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