Viscous and filamentous bulking in activated sludge: Rheological and hydrodynamic modelling based on experimental data. (1st May 2022)

• Record Type: Journal Article
• Authors: Bakos, V.; Gyarmati, B.; Csizmadia, P.; Till, S.; Vachoud, L.; Nagy Göde, P.; Tardy, G.M.; Szilágyi, A.; Jobbágy, A.; Wisniewski, C.
• Is Part Of: Water research. Volume 214(2022)
• Publication Date: 2022-05-01
• Subjects: Activated sludge -- Filamentous bulking -- Viscous bulking -- Non-Newtonian flow -- Computational fluid dynamics -- Hydrodynamics; 00-01 -- 99-00; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2022.118155
• Languages: English
• ISSNs: 0043-1354

Abstract

Highlights: A novel protocol has been developed for rheological and hydrodynamic modelling. The entire development of viscous and filamentous bulking was examined by rheology. Viscosity curves provided guidance for indicating development of sludge bulking. Viscous bulking stronger impacts flow behavior than the overgrowth of filaments. The methodology developed is useful for increasing sludge pumping energy efficiency. Graphical abstract: Abstract: Although achieving good activated sludge settleability is a key requirement for meeting effluent quality criteria, wastewater treatment plants often face undesired floc structure changes. Filamentous bulking has widely been studied, however, viscous sludge formation much less investigated so far. Our main goal was to find relationship between sludge floc structure and related rheological properties, moreover, to estimate pressure loss in pipe networks through hydrodynamic modelling of the non-Newtonian flows in case of well settling (ideal-like), viscous and filamentous sludge. Severe viscous and filamentous kinds of bulking were generated separately in continuous-flow lab-scale systems initially seeded with the same reference (ideal-like) biomass and the entire evolution of viscous and filamentous bulking was monitored. The results suggested correlation between the rheological properties and the floc structure transformations, and showed the most appropriate fit for the Herschel-Bulkley model (vs. Power-law and Bingham). Validated computational fluid dynamics studies estimated the pipe pressure loss in a wide Reynolds number range for the initial well settling (reference) and the final viscous and filamentous sludge as well. A practical standard modelling protocol was developed for improving energy efficiency of sludge pumping in different floc structure scenarios.