Abstract
Aerobic granular sludge (AGS) technology allows simultaneous nitrogen, phosphorus, and carbon removal in compact wastewater treatment processes. To operate, design, and model AGS reactors, it is essential to properly understand the diffusive transport within the granules. In this study, diffusive mass transfer within full‐scale and lab‐scale AGS was characterized with nuclear magnetic resonance (NMR) methods. Self‐diffusion coefficients of water inside the granules were determined with pulsed‐field gradient NMR, while the granule structure was visualized with NMR imaging. A reaction‐diffusion granule‐scale model was set up to evaluate the impact of heterogeneous diffusion on granule performance. The self‐diffusion coefficient of water in AGS was ∼70% of the self‐diffusion coefficient of free water. There was no significant difference between self‐diffusion in AGS from full‐scale treatment plants and from lab‐scale reactors. The results of the model showed that diffusional heterogeneity did not lead to a major change of flux into the granule (<1%). This study shows that differences between granular sludges and heterogeneity within granules have little impact on the kinetic properties of AGS. Thus, a relatively simple approach is sufficient to describe mass transport by diffusion into the granules.
Highlights
Self‐diffusion coefficients of water inside the granules were determined with pulsed‐field gradient nuclear magnetic resonance (NMR), while the granule structure was visualized with NMR imaging
There was no significant difference between self‐diffusion in Aerobic granular sludge (AGS) from full‐scale treatment plants and from lab‐scale reactors
Diffusive mass transfer within lab‐scale and full‐scale AGS has been characterized with Pulsed‐field gradient nuclear magnetic resonance (PFG‐NMR)
Summary
Installations have been built (Pronk, Giesen, Thomphson, Robertson, & van Loosdrecht, 2017; van der Roest, de Bruin, Aerobic granular sludge (AGS) is an advanced technology for the Gademan, & Coelho, 2011). The simultaneous nitrification and denitrification require a careful balance between the aerobic and the anoxic volume of the granules (Di Bella & Torregrossa, 2013; Mosquera‐Corral, de Kreuk, Heijnen, & van Loosdrecht, 2005; Yilmaz, Lemaire, Keller, & Yuan, 2008) These processes can only occur at the same time within a granule if the nitrification reaction is diffusion limited (Daigger & Littleton, 2014). Mass transfer limitation can lead to filamentous outgrowth or hollow cores in the granule Both phenomena have been shown to notably reduce reactor performance (de Kreuk, Kishida, Tsuneda, & van Loosdrecht, 2010; Zheng, Yu, Liu, & Liu, 2006). We provided a recommendation on how to include diffusion in the analysis of AGS kinetic properties and in AGS modeling
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.