2/21/2023 0 Comments Viscosity of water![]() ![]() It stands to reason that the viscosity affects the shear at the membrane interface, shear being a key parameter in promoting flux, and that the dependency of apparent viscosity on temperature may then also be significant in determining flux. The non-Newtonian nature of sewage sludge means that its measured viscosity µs, referred to as 'apparent viscosity', varies with shear rate due to the shear-dependent deformation of the flocculant solids (Yang et al, 2009). Whilst water behaves as a simple Newtonian fluid, with a temperature dependence which is absolutely predictable, sewage sludge displays thixotropic properties (Seyssiecq et al, 2003) and is often defined rheologically as a Bingham plastic whose apparent viscosity changes with both shear rate and solids concentration (Yang et al, 2009). The rheological properties of both water and sludge are widely understood. So, just how do sludge filterability and viscosity change with the key property of temperature? This is possibly the simplest, and the most ubiquitous, relationship to consider. High-SSVI sludges are often associated with filamentous micro organisms, which are widely known to generate a high resistance to sludge filtration due in part to the hydrophobic nature of the micro organisms. While it may be presumed that the filtration-based parameters of CST and TTF may provide a reasonable basis for determining the membrane permeability, it is likely that the simple SSVI measurement is a better measure. In practice, a rough-and-ready indication of bulk sludge quality is provided by (specific) sludge volume index ((S)SVI), capillary suction time (CST) and time to filter (TTF). M|MBR Systems’ modular MBR solutions get fully functioning wastewater treatment running in weeks, not months. a sludge bulk property (viscosity) with another sludge bulk property (temperature, concentration or composition).flux, permeability and fouling rate with a sludge bulk property (viscosity or temperature), or.Such studies can be roughly divided into those generating correlations between: There are a number of excellent publications on the subject from various research groups around the world, including studies of pilot and full-scale plants. On occasions, researchers have taken time off from characterising foulant chemistry in MBR sludge to take a look at its bulk properties. There are a number of possible explanations for this, but perhaps the most obvious of these is that bulk sludge filterability depends on more than just chemistry and biochemistry, and specifically on the multifarious and very complex impacts of the microbial ecology. In general, whilst some correlations have been produced successfully, none extend across multiple full-scale plants. Hundreds of papers have been produced based on correlation of membrane fouling with specific candidate foulant species − chemicals, biochemicals or particles of a specific size range. The focus of a significant section of the MBR scientific community from the late 90s onwards has centred on the idea of some measurable MBR sludge quality which can be used to predict permeability, preferably through on-line measurement. ![]()
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