The effects of transient nitrogen loadings on nitrifying activated sludges in completely mixed and plug-flow reactors

Horan, N. J.; Azimi, A A

doi:10.1016/0043-1354(92)90024-x

Cited by 14 publications

(12 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Ef®ciency of nitri®cation increased with increasing sludge age and remained constant for h c ³ 12 d. Minimum h c resulting in maximum nitri®cation ef®ciency was 12 d. Similarly hydraulic residence times (h H ) lower than 15 h resulted in unacceptable levels of NH 4 79 rate above 150 mg N/h resulted in signi®cant levels of NO x ±N in the ef¯uent of denitri®cation reactor. Therefore, NO x ±N loading rate should be lower than 150 mgN/h, for nearly complete denitri®cation.…”

Section: Discussionmentioning

confidence: 99%

Effects of operating parameters on performances of nitrification and denitrification processes

Dinçer

Kargı

2000

Bioprocess Engineering

View full text Add to dashboard Cite

Nitri®cation and denitri®cation of synthetic wastewater was studied by using two reactors in series. An activated sludge unit was used for nitri®cation followed by a down¯ow bio®lter (packed column) for denitri®ca-tion. A glucose solution was fed to the denitri®cation column to supply carbon source. Effects of important process variables such as sludge age, hydraulic residence time and feed ammonium concentration on system's performance were investigated. Ef¯uent ammonium±ni-trogen (NH4±N) concentration decreased with increasing sludge age and hydraulic residence time and remained constant for sludge age and hydraulic residence times greater than 12 d and 15 h, respectively. Feed ammonium± nitrogen concentration above 200 mg/l resulted in signi®cant levels of NH4±N in the ef¯uent at h c = 15 d and h H = 12 h in nitri®cation. Performance of denitri®cation stage was not satisfactory for feed NO 3 ±N concentrations above 150 mg N/l resulting in signi®cant ef¯uent NO 3 ±N levels at hydraulic residence time of h H = 6 h.

show abstract

Section: Discussionmentioning

confidence: 99%

Effects of operating parameters on performances of nitrification and denitrification processes

Dinçer

Kargı

2000

Bioprocess Engineering

View full text Add to dashboard Cite

show abstract

“…Although NH þ 4 can cause nitrite accumulation (e.g., Horan and Azimi 1992;Smith et al 1997), the effect of free ammonia seems to be more pronounced. FA is a competitive inhibitor of NOR activity, which is located on the cell membrane of NOB (Yang and Alleman 1992).…”

Section: Ph and Free Ammonia And Nitrous Acid Concentrationsmentioning

confidence: 94%

Partial nitrification—operational parameters and microorganisms involved

Sinha

Annachhatre

2006

Rev Environ Sci Biotechnol

164

View full text Add to dashboard Cite

Nitrite is a common intermediate in at least three different oxidative or reductive biochemical pathways that occur in nature (nitrification, denitrification and dissimilatory or assimilatory nitrate reduction). Nitrite accumulation or partial nitrification has been reported in literature for decades. In engineered systems, partial nitrification is of interest as it offers cost savings in aeration as well as in the form of lesser need for addition of organic carbon as compared to the conventional denitrification. A broad range of operating parameters and factors has been reviewed in this paper which are essential for achieving partial nitrification. Of these, pH, dissolved oxygen (DO), temperature, free ammonia (FA) and nitrous acid concentrations, inhibitory compounds are important factors in achieving partial nitrification.Two groups of bacteria, namely ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) are involved in nitrification. Chemolitho-autotrophic AOB are responsible for the rate-limiting step of nitrification in a wide variety of environments, making them important in the global cycling of nitrogen. Characterization

show abstract

“…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

View full text Add to dashboard Cite

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.

show abstract

The effects of transient nitrogen loadings on nitrifying activated sludges in completely mixed and plug-flow reactors

Cited by 14 publications

References 7 publications

Effects of operating parameters on performances of nitrification and denitrification processes

Effects of operating parameters on performances of nitrification and denitrification processes

Partial nitrification—operational parameters and microorganisms involved

Conditions for partial nitrification in biofilm reactors and a kinetic explanation

Contact Info

Product

Resources

About