RMIT University, School of Civil, Environmental and Chemical Engineering, 124 La Trobe St, Melbourne, Vic 3000, Australia.
RMIT University, School of Civil, Environmental and Chemical Engineering, 124 La Trobe St, Melbourne, Vic 3000, Australia.
Water Res. 2018 May 1;134:86-91. doi: 10.1016/j.watres.2018.01.071. Epub 2018 Feb 3.
Xanthan gum is widely used as a model fluid for sludge to mimic the rheological behaviour under various conditions including impact of gas injection in sludge. However, there is no study to show the influence of gas injection on rheological properties of xanthan gum specifically at the concentrations at which it is used as a model fluid for sludge with solids concentration above 2%. In this paper, the rheological properties of aqueous xanthan gum solutions at different concentrations were measured over a range of gas injection flow rates. The effect of gas injection on both the flow and viscoelastic behaviour of Xanthan gum (using two different methods - a creep test and a time sweep test) was evaluated. The viscosity curve of different solid concentrations of digested sludge and waste activated sludge were compared with different solid concentrations of Xanthan gum and the results showed that Xanthan gum can mimic the flow behaviour of sludge in flow regime. The results in linear viscoelastic regime showed that increasing gas flow rate increases storage modulus (G'), indicating an increase in the intermolecular associations within the material structure leading to an increase in material strength and solid behaviour. Similarly, in creep test an increase in the gas flow rate decreased strain%, signifying that the material has become more resistant to flow. Both observed behaviour is opposite to what occurs in sludge under similar conditions. The results of both the creep test and the time sweep test indicated that choosing Xanthan gum aqueous solution as a transparent model fluid for sludge in viscoelastic regime under similar conditions involving gas injection in a concentration range studied is not feasible. However Xanthan gum can be used as a model material for sludge in flow regime; because it shows a similar behaviour to sludge.
黄原胶被广泛用作污泥的模型流体，以模拟各种条件下的流变行为，包括在污泥中注入气体的影响。然而，目前还没有研究表明气体注入对黄原胶流变性能的影响，特别是在浓度为 2%以上的情况下，因为它被用作污泥的模型流体。本文在不同的气体注入流速范围内测量了不同浓度的水溶液黄原胶的流变性质。评价了气体注入对黄原胶的流动和粘弹行为（使用两种不同的方法——蠕变试验和时间扫描试验）的影响。比较了不同固体浓度的消化污泥和剩余活性污泥的粘度曲线与不同固体浓度的黄原胶，结果表明黄原胶可以模拟污泥在流动状态下的流动行为。在线性粘弹区的结果表明，增加气体流速会增加储能模量（G'），这表明材料结构内的分子间缔合增加，导致材料强度和固体行为增加。同样，在蠕变试验中，气体流速的增加会降低应变%，表明材料对流动的阻力更大。这两种观察到的行为与类似条件下污泥的行为相反。蠕变试验和时间扫描试验的结果表明，在类似条件下，在研究的浓度范围内注入气体时，选择黄原胶水溶液作为粘弹区中污泥的透明模型流体是不可行的。然而，黄原胶可以作为污泥的模型材料用于流动区，因为它表现出与污泥相似的行为。
