The influence of reactor mixing characteristics on the rate of nitrification in the activated sludge process

Azimi, A A; Horan, N. J.

doi:10.1016/0043-1354(91)90078-5

Cited by 18 publications

(9 citation statements)

References 9 publications

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“…The percentage aerobic portion was found to be unchanged due to an increase in nitrate bulk concentration. This is compatible with the experimental study by Kornaros et al [17] ; Azimi and Horan [18] . It was found also that the percentage aerobic ratio increases with increasing substrate diffusivity.…”

Section: Resultssupporting

confidence: 93%

Modeling of Activated Sludge Floc Characteristics

Mustafa¹,

Ibrahim²,

Elkamel³

et al. 2009

American Journal of Environmental Sciences

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Problem Statement: The activated sludge system needs to improve the operational performance and to achieve more effective control. To realize this, a better quantitative understanding of the biofloc characteristics is required. The objectives of this study were to: (i) Study the biofloc characteristics from kinetics-mass transfer interaction point of view by quantification of the weight of the aerobic portion of the activated sludge floc to the total floc weight. (ii) Study the effect of bulk concentrations of oxygen and nitrates, power input and substrates diffusivity on the portion aerobic portion of the floc. Approach: An appropriate mathematical model based on heterogeneous modeling is developed for activated sludge flocs. The model was taking into account three growth processes: Carbon oxidation, nitrification and de-nitrification in terms of four components: substrate, nitrate, ammonia, and oxygen. The model accounts for the internal and external mass transfer limitations and relates the external mass transfer resistance with power input. The floc model equations were two- point boundary value differential equations. Therefore a central finite difference method is employed. Results: The percentage aerobic portion increased with increasing with oxygen bulk concentrations and power input and decreases when the bulk concentration of ammonia and substrate increases. Both will compete to consume the internal oxygen by autotrophic and heterotrophic bacteria through aerobic growth processes. The biofloc activity through the profiles was either totally active or partially active. The totally active biofloc is either totally aerobic or aerobic and anoxic together. Conclusions: The heterogeneous floc model was able to describe the biofloc characteristics and reflects the real phenomena existing in the activated sludge processes

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Section: Resultssupporting

confidence: 93%

Modeling of Activated Sludge Floc Characteristics

Mustafa¹,

Ibrahim²,

Elkamel³

et al. 2009

American Journal of Environmental Sciences

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“…In addition, the influence of liquid phase mixing on nitrifying system performance has been the objective of previous research (Azimi and Horan, 1991;Horan and Azimi, 1992 for activated sludge systems, Watten and Sibrell, 2006 for biofilm reactors). These studies focused on the effect of liquid phase mixing on conversion, showing that plug-flow reactors perform better since the higher substrate concentration in the bulk liquid along the first part of the plug-flow reactor increases conversion although at the same time increasing any inhibition effects due to higher concentrations of ammonium and nitrite (i.e., free ammonia and free nitrous acid) (Azimi and Horan, 1991;Horan and Azimi, 1992;Watten and Sibrell, 2006).…”

Section: Introductionmentioning

confidence: 99%

“…These studies focused on the effect of liquid phase mixing on conversion, showing that plug-flow reactors perform better since the higher substrate concentration in the bulk liquid along the first part of the plug-flow reactor increases conversion although at the same time increasing any inhibition effects due to higher concentrations of ammonium and nitrite (i.e., free ammonia and free nitrous acid) (Azimi and Horan, 1991;Horan and Azimi, 1992;Watten and Sibrell, 2006). However, these studies did not examine the effect of liquid phase mixing on compartmentalization of AOB and NOB populations in nitrifying biofilm reactors.…”

Section: Introductionmentioning

confidence: 99%

Conditions for partial nitrification in biofilm reactors and a kinetic explanation

Pérez

Costa

Kreft

2009

Biotech & Bioengineering

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Nitrification is a two-step process in which ammonia is incompletely oxidized by ammonia-oxidizing bacteria or archaea (AOB) to nitrite, which is then further oxidized to nitrate by nitrite-oxidizing bacteria (NOB). Literature reports show that segregation of initially coexisting ammonia and nitrite oxidizing populations co-immobilized in gel cubes and cultured in a set-up with three reactors in series (without recirculation) is attained. In those studies NOB were present and nitrite was oxidized mainly in the last reactor. We developed a mathematical model for immobilized biomass that allows for one-dimensional gradients of metabolites and changes of porosity within the gel due to growth. The model reproduced the experimentally observed compartmentalization under the conditions used by Noto et al. (Noto et al., 1998. Water Res 32(3): 769- 773), using standard kinetic parameters of nitrifying bacteria including free ammonia inhibition of AOB and NOB. The model predicted compartmentalization when the ammonium load was sufficiently high and liquid phase mixing sufficiently limited (close to plug-flow). Modeling results demonstrated that inhibition of NOB by free ammonia did not substantially contribute to the compartmentalization in biofilm reactors. Additional simulations identified the higher oxygen affinity of AOB as the key parameter leading to compartmentalization (i.e., partial nitrification) in artificial and natural biofilms since they enable the formation of oxygen gradients. As a result, a tendency for compartmentalization was found even at equal competitiveness.

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“…The investigation of the influence of hydrodynamic conditions on the kinetics of the nitrification process Chudoba et al [26] showed that the gradual flow system is more advantageous for the nitrification process compared to the mixing system [26]. Azimi and Horan [27] also presented the advantages of a gradual flow nitrification system under steady state conditions [27]. Similar results were also published by Horan and Azimi [28] based on the investigation of the responses of nitrification systems with different hydrodynamic conditions to a sudden increase in nitrogen pollution [28].…”

Section: Single Anoxic Systemmentioning

confidence: 99%

Nutrient Removal and Recovery from Municipal Wastewater

Derco,

Žgajnar Gotvajn,

Guľašová

et al. 2024

Preprint

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With the ongoing amendment of the EU legislation on the treatment of urban wastewater, stricter requirements for the removal of pollutants are expected, which calls for the need for innovative wastewater treatment technologies. Biological systems are still the first choice. The survey of typical bioreactors applied in wastewater treatment is presented. Wastewater treatment objective, bio-chemical environment and microbial growth are selected as a main criterion for classification of these bioreactors. Hydraulic and kinetic aspects are considered, advantages and drawbacks of these bioreactors regarding the selection of appropriate type of the reactor as well as regarding operation of reactors are mentioned. The aim of this paper is to provide operators and designers with a brief overview of selected traditional and advanced processes, reactors, and technologies for nutrient removal from municipal wastewater. Another goal is to discuss the possibilities and limitations to comply with more strict effluent standards. From the evaluation of the published papers, it follows that the currently applied traditional methods of nutrients removal have the potential to convey also with the expected stricter limits.

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The influence of reactor mixing characteristics on the rate of nitrification in the activated sludge process

Cited by 18 publications

References 9 publications

Modeling of Activated Sludge Floc Characteristics

Modeling of Activated Sludge Floc Characteristics

Conditions for partial nitrification in biofilm reactors and a kinetic explanation

Nutrient Removal and Recovery from Municipal Wastewater

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