The granule size distribution in an anammox‐based granular sludge reactor affects the conversion—Implications for modeling

Abstract

Mathematical models are useful tools to optimize the performance of granular sludge reactors. In these models, typically a uniform granule size is assumed for the whole reactor, even though in reality the granules follow a size distribution and the granule size as such affects the process performance. This study assesses the effect of the granule size distribution on the performance of a granular sludge reactor in which autotrophic nitrogen removal is realized through one-stage partial nitritation-anammox. A comparison is made between different approaches to deal with particle size distributions in one-dimensional biofilm models, from the use of a single characteristic diameter to applying a multiple compartment model. The results show a clear impact on the conversion efficiency of the way in which particle size distribution is modeled, resulting from the effect of the granule size on the competition between nitrite oxidizing and anammox bacteria and from the interaction between granules of different sizes in terms of the exchange of solutes. Whereas the use of a uniform granule size is sufficient in case only the overall reactor behavior needs to be assessed, taking into account the detailed granule size distribution is required to study the solute exchange between particles of different sizes. For the latter purpose, the application of the widespread software package Aquasim is limited and the development of dedicated software applications is required.

Three-Dimensional Stratification of Bacterial Biofilm Populations in a Moving Bed Biofilm Reactor for Nitritation-Anammox

“…In continuous reactors on the other hand, the microbial groups need to be separated in space, with anammox bacteria residing in anoxic zones of the microbial aggregates, provided by the oxygen demanding activities of AOB. In microbial granules, distinct patterns of stratification have been predicted by modelling and observed with microbiological methods, with AOB being located in the outer aerobic zone near the water interface and with anammox bacteria in the inner anoxic parts [4–8]. For nitritation-anammox biofilms on fixed substrata, the observed localization of microorganisms has been less straightforward.…”

Population balance models: a useful complementary modelling framework for future WWTP modelling

“…Furthermore, the Winkler et al remarked on the dominance in the floccular fraction of both reactors of AOO via FISH analyses. Volcke et al (2012) assessed the influence of a non-uniform granule size distribution on granular nitritation-anammox reactor macroscale and microscale characteristics, and concluded that size distribution influences microscale solute transport due to increased relative abundance of AOO in smaller granules and AMO in larger granules. Interestingly, our model indicated a similar segregation of microbial populations and activities due to the inclusion of a second biomass fraction without mass transport limitations (flocs), with AMO concentrated in (uniform size distribution) granules and AOO predominating in floccular biomass.…”

“…different microbial consortia at different locations in the agglomerate), the simulation of such a microenvironment within a macro-scale fluid transport environment has hardly been performed. Recently, Volcke et al (2012) demonstrated the significant impact of granule size distribution on the performance of an Anammox-based granular sludge reactor. The authors used a fixed size distribution for this analysis.…”

Towards Predictive Models of the Human Gut Microbiome

“…The operational variables include aeration, mixing and flow rate, which if not optimally chosen can lead to bioreactor failure 8 . Mathematical models can be valuable tools to assist in the operation and control of these bioreactors, to enrich microbial composition in the right type of microbes 9 .…”