Sludge formation in the activated sludge process with a sludge disintegration unit

Alharbi, Asma Olyan M.; Nelson, Mark; Worthy, Annette L.; Sidhu, Harvinder

doi:10.21914/anziamj.v55i0.7803

Cited by 3 publications

(16 citation statements)

References 3 publications

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“…The leading order term for the chemical oxygen demand is identical to both that in our earlier model [1] and in the basic model [12]. The leading order term for the volatile suspended solids is also identical provided that there are no non-biodegradable particulates in the feed, i.e.…”

Section: Asymptotic Solutionsmentioning

confidence: 58%

“…It is interesting to observe that the expression for the substrate concentration is identical to that when the dead biomass is recycled into the soluble substrate pool [1]. Indeed they are both identical to the expression in the basic model [12].…”

Section: Resultsmentioning

confidence: 75%

“…The steady-state expressions for the washout branch are equivalent to the expressions when dead biomass is recirculated into the pool of soluble substrate [1]. This is unsurprising as the biochemistry of the two models are identical when there is no biomass present in the reactor (X * b = 0).…”

Section: Resultsmentioning

confidence: 99%

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Analysis of an activated sludge model in which dead biomass is recycled into slowly biodegradable particulate substrate

Alharbi

Nelson

Worthy

et al. 2015

Asia-Pacific J Chem Eng

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A significant drawback of the activated sludge process is the production of excess 'sludge'; the disposal of which can account for 50-60% of the running costs of a wastewater treatment plant. We investigate a model for the activated sludge process in which the influent contains a mixture of soluble and slowly biodegradable particulate substrate. Within the bioreactor, the particulate substrate is hydrolyzed to form soluble substrate. In turn, these are used for growth by the biomass. Biomass decay produces slowly biodegradable substrate and non-biodegradable particulates. Steady-state analysis is used to investigate how the amount of sludge formed depends upon the residence time and the use of a settling unit. We show that when the steady-state sludge content is plotted as a function of the residence time that there are three generic response diagrams. The value of the effective recycle parameter determines which type of response diagram is observed. If this parameter is greater than a critical value, then the sludge content is guaranteed to be greater than a target value. The dependence of this critical value upon the chemical oxygen demand in the feed and how the chemical oxygen demand is partitioned between its constitutive components is investigated. (2) School of Physical, Environmental and Mathematical Science, UNSW at ADFA, Canberra, ACT 2600, Australia Disciplines Engineering | Science and Technology StudiesNovember 15, 2014 AbstractThe activated sludge process is one of the major processes used in the biological treatment of wastewater.A significant drawback of this process is the production of excess sludge, the disposal of which can account for 50-60% of the running costs of a plant.We investigate a model for the activated sludge process in which the influent contains a mixture of soluble and slowly biodegradable particulate substrate. Within the bioreactor the biodegradable particulate substrate is hydrolyzed to form soluble substrate. In turn these are used for growth by the biomass. Biomass decay produces slowly biodegradable substrate in addition to non-biodegradable particulates.We use steady-state analysis to investigate how the amount of sludge formed depends upon the residence time and the use of a settling unit. We show that when the steady-state sludge content is plotted as a function of the residence time that there are three generic response diagrams, depending upon the value of the effective recycle parameter. We find that if the effective recycle parameter is higher than a critical value then sludge content is guaranteed to be greater than a target value. We investigate how this critical value depends upon the chemical oxygen demand in the feed and how the chemical oxygen demand is partitioned between its constitutive components.

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Section: Asymptotic Solutionsmentioning

confidence: 58%

Section: Resultsmentioning

confidence: 75%

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Analysis of an activated sludge model in which dead biomass is recycled into slowly biodegradable particulate substrate

Alharbi

Nelson

Worthy

et al. 2015

Asia-Pacific J Chem Eng

Self Cite

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“…A. O. M. Alharbi [2] In Chapter 4 a seemingly minor modification is made to the model in Chapter 2. Instead of biomass decay producing soluble substrate and inert material, it produces slowly biodegradable substrate and nonbiodegradable particulates.…”

Section: Introductionmentioning

confidence: 99%

“…Unlike the model investigated in Chapter 2, we find that in practice excessive sludge formation is inevitable. The results of the successive stages of this research have been published in [1][2][3].…”

Section: Introductionmentioning

confidence: 99%

The Biological Treatment of Wastewater: Mathematical Models

Alharbi

2016

Bull. Aust. Math. Soc.

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A mathematical model for the activated sludge process with a sludge disintegration unit

Alsaeed

Nelson

Edwards

et al. 2022

Chemical Product and Process Modeling

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We develop and investigate a model for sludge production in the activated sludge process when a biological reactor is coupled to a sludge disintegration unit (SDU). The model for the biological reactor is a slimmed down version of the activated sludge model 1 in which only processes related to carbon are retained. Consequently, the death-regeneration concept is included in our model which is an improvement on almost all previous models. This provides an improved representation of the total suspended solids in the biological reactor, which is the key parameter of interest. We investigate the steady-state behaviour of this system as a function of the residence time within the biological reactor and as a function of parameters associated with the operation of the SDU. A key parameter is the sludge disintegration factor. As this parameter is increased the concentration of total suspended solids within the biological reactor decreases at the expense increasing the chemical oxygen demand in the effluent stream. The existence of a maximum acceptable chemical oxygen demand in the effluent stream therefore imposes a maximum achievable reduction in the total suspended solids. This paper improves our theoretical understanding of the utility of sludge disintegration as a means to reduce excess sludge formation. As an aside to the main thrust of our paper we investigate the common assumption that the sludge disintegration processes occur on a much shorter timescale than the biological processes. We show that the disintegration processes must be exceptional slow before the inclusion of the biological processes becomes important.

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Sludge formation in the activated sludge process with a sludge disintegration unit

Cited by 3 publications

References 3 publications

Analysis of an activated sludge model in which dead biomass is recycled into slowly biodegradable particulate substrate

Analysis of an activated sludge model in which dead biomass is recycled into slowly biodegradable particulate substrate

The Biological Treatment of Wastewater: Mathematical Models

A mathematical model for the activated sludge process with a sludge disintegration unit

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