Steady-state analyses of activated sludge processes with plug-flow reactor

Diehl, Stefan; Zambrano, Jesús; Carlsson, Bengt

doi:10.1016/j.jece.2016.06.038

Cited by 8 publications

(18 citation statements)

References 36 publications

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“…The development of more detailed models for dynamic simulations is an active area of research. An example of such a model is the one‐dimensional hindered‐compression‐dispersion model due to Bürger and Diehl, which has been used in a number of recent publications . A significant problem associated with the use of more detailed settling unit models is obtaining the necessary experimental data to calibrate them.…”

Section: Equationsmentioning

confidence: 99%

An analysis of organic carbon removal in a two‐reactor cascade with recycle and a two‐reactor step‐feed cascade with recycle

Nelson

Bradshaw‐Hajek

2019

Asia-Pacific J Chem Eng

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We analyse the steady-state operation of two process configurations that employ a reactor cascade with recycle. The first process configuration is a two-reactor cascade in which the feed stream enters into the first reactor. The second process configuration is a two-reactor step-feed cascade in which the feed stream enters the second reactor. In each process configuration, part of the effluent stream is recycled back into the first reactor. The reactors in the cascade need not be of equal volume. The reaction is assumed to be a biological process governed by Monod growth kinetics with a decay coefficient for the microorganisms. The stability of the washout solution is determined analytically for both process configurations. It follows from the stability analysis that that there is a range of residence times over which the effluent concentration leaving a step-reactor cascade is lower than that leaving a standard reactor cascade. Steady-state diagrams are presented showing the effluent concentration as a function of the residence time. We find that if the desired effluent concentration is not too low, then the process configuration that minimises the residence time is the step-feed reactor cascade. However, for much cleaner waste streams, the process configuration that minimises the residence time is the standard reactor cascade.KEYWORDS activated sludge, multistage continuous culture, staging, step-feed reactor, wastewater, water treatment Asia-Pac J Chem Eng. 2020;15:e2392.wileyonlinelibrary.com/journal/apj

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Section: Equationsmentioning

confidence: 99%

An analysis of organic carbon removal in a two‐reactor cascade with recycle and a two‐reactor step‐feed cascade with recycle

Nelson

Bradshaw‐Hajek

2019

Asia-Pacific J Chem Eng

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“…It is useful when the main focus is on the overall behaviour of the system. Diehl et al noted that "It is the most commonly used assumption for steady-state analysis in text books and papers" [10,Section 7]. However, when modelling dynamic conditions activated sludge models are mostly coupled with one-dimensional settling unit models [11].…”

Section: The Ideal Settling Unit Modelmentioning

confidence: 99%

“…Diehl et al [9] modelled the bioreactor as a continuously stirred tank reactor. In a complementary study, the bioreactor was instead assumed to be a plug-flow reactor [10]. As before, the authors assumed that the reactor cannot be overloaded and varied the recycle ratio and the wastage ratio to ensure that the location of the sludge blanket remains fixed at 1 m. One point of difference is that the steady-state solutions obtained using the Bürger-Diehl settling tank model were compared to those using the ideal settling tank model.…”

Section: Other Models For the Settling Unitmentioning

confidence: 99%

Mathematical Modelling of the Removal of Organic Micropollutants in the Activated Sludge Process: A Linear Biodegradation Model

Nelson¹,

Alqahtani²,

Hai³

2018

ANZIAM J.

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Before wastewaters can be released into the environment, they must be treated to reduce the concentration of organic pollutants in the effluent stream. There is a growing concern as to whether wastewater treatment plants are able to effectively reduce the concentration of micropollutants that are also contained in their influent streams. We investigate the removal of micropollutants in treatment plants by analysing a model that includes biodegradation and sorption as the main mechanisms of micropollutant removal. For the latter a linear adsorption model is used in which adsorption only occurs onto particulates.The steady-state solutions of the model are found and their stability is determined as a function of the residence time. In the limit of infinite residence time, we show that the removal of biodegradable micropollutants is independent of the processes of adsorption and desorption. The limiting concentration can be decreased by increasing the concentration of growth-related macropollutants. Although, in principle, it is possible that the concentration of micropollutants is minimized at a finite value of the residence time, this was found not to be the case for the particular biodegradable micropollutants considered.For nonbiodegradable pollutants, we show that their removal is always optimized at a finite value of the residence time. For finite values of the residence time, we obtain a simple condition which identifies whether biodegradation is more or less efficient than adsorption as a removal mechanism. Surprisingly, we find that, for the micropollutants considered, adsorption is always more important than biodegradation, even when the micropollutant is classified as being highly biodegradable with low adsorption.

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“…Moreover, most of the mathematical analysis available in the literature consider a spatial heterogeneity only in the axial dimension of the bioreactors (leading to 1d p.d.e. or compartments connected in series) as in tubular or "plug-flow" bioreactors [12,7,9,61,6] and (simple) gradostats [32,33,56,52]. Surprisingly, configurations of tanks in parallel rather than in series have been much less investigated, apart simple considerations in chemical reaction engineering [31,11].…”

Section: Introductionmentioning

confidence: 99%

Analysis and Optimization of the Chemostat Model with a Lateral Diffusive Compartment

Crespo

Rapaport

2020

J Optim Theory Appl

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We consider the classical chemostat model with an additional compartment connected by pure diffusion, and analyze its asymptotic properties. We investigate conditions under which this spatial structure is beneficial for species survival and yield conversion, compared to single chemostat. Moreover we look for the best structure (volume repartition and diffusion rate) which minimizes the volume required to attain a desired yield conversion. The analysis reveals that configurations with a single tank connected by diffusion to the input stream can be the most efficient.

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Steady-state analyses of activated sludge processes with plug-flow reactor

Cited by 8 publications

References 36 publications

An analysis of organic carbon removal in a two‐reactor cascade with recycle and a two‐reactor step‐feed cascade with recycle

An analysis of organic carbon removal in a two‐reactor cascade with recycle and a two‐reactor step‐feed cascade with recycle

Mathematical Modelling of the Removal of Organic Micropollutants in the Activated Sludge Process: A Linear Biodegradation Model

Analysis and Optimization of the Chemostat Model with a Lateral Diffusive Compartment

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