External carbon source addition as a means to control an activated sludge nutrient removal process

Isaacs, S.; Henze, Mogens; Søeberg, H.; Kümmel, M.

doi:10.1016/0043-1354(94)90002-7

Cited by 72 publications

(28 citation statements)

References 6 publications

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“…For example, it was shown that acetate as the major carbon source in a laboratory-scale reactor selected for denitrifiers with nonflocculating properties, which would adversely affect sedimentation if they became abundant (8). Methanol addition to activated sludge often requires an adaptation period of up to several months before its effect on denitrification rates is fully recognized, but the response to ethanol or acetate seems to be faster (12,13,19,22,25,29). Recent studies have shown that ethanol and acetate select for the Azoarcus, Dechloromonas, Thauera, and Acidovorax-like denitrifiers commonly found in treatment processes, which could explain the rapid adaptation to these external carbon sources (8, 17).…”

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confidence: 99%

“…In the ideal activated sludge process, bacteria denitrify by using carbon compounds in the influent wastewater as electron donors. As a means to improve control strategies for nitrogen removal, external carbon compounds can be added to enhance denitrification rates (10,14,18,19,34,35). Higher rates allow reductions in the hydraulic retention time in the anoxic zones, making it possible to minimize basin volumes (23).…”

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Metabolic Profiles and Genetic Diversity of Denitrifying Communities in Activated Sludge after Addition of Methanol or Ethanol

Hallin

Throbäck

Dicksved

et al. 2006

Appl Environ Microbiol

102

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External carbon sources can enhance denitrification rates and thus improve nitrogen removal in wastewater treatment plants. The effects of adding methanol and ethanol on the genetic and metabolic diversity of denitrifying communities in activated sludge were compared using a pilot-scale plant with two parallel lines. A full-scale plant receiving the same municipal wastewater, but without external carbon source addition, was the reference. Metabolic profiles obtained from potential denitrification rates with 10 electron donors showed that the denitrifying communities altered their preferences for certain compounds after supplementation with methanol or ethanol and that methanol had the greater impact. Clone libraries of nirK and nirS genes, encoding the two different nitrite reductases in denitrifiers, revealed that methanol also increased the diversity of denitrifiers of the nirS type, which indicates that denitrifiers favored by methanol were on the rise in the community. This suggests that there might be a niche differentiation between nirS and nirK genotypes during activated sludge processes. The composition of nirS genotypes also varied greatly among all samples, whereas the nirK communities were more stable. The latter was confirmed by denaturing gradient gel electrophoresis of nirK communities on all sampling occasions. Our results support earlier hypotheses that the compositions of denitrifier communities change during predenitrification processes when external carbon sources are added, although no severe effect could be observed from an operational point of view.Considerable efforts have been made to improve the technology for efficient and economic removal of nitrogen by denitrification in municipal activated sludge. Denitrification is an anaerobic microbial respiration process with a stepwise reduction of nitrate or nitrite via nitric oxide to nitrous oxide or dinitrogen. In the ideal activated sludge process, bacteria denitrify by using carbon compounds in the influent wastewater as electron donors. As a means to improve control strategies for nitrogen removal, external carbon compounds can be added to enhance denitrification rates (10,14,18,19,34,35). Higher rates allow reductions in the hydraulic retention time in the anoxic zones, making it possible to minimize basin volumes (23). For this purpose, methanol and ethanol are most commonly used in practice, although acetate has been reported to give the highest rates in most cases (12,24,(28)(29)(30).Although much is known about process performance after the addition of external carbon sources, little effort has been made to explain the specific effects on the denitrifying communities in activated sludge. The selective pressure from the carbon compound added might affect the composition of the denitrifying community, which would influence metabolic diversity and functional properties of the denitrifiers. For example, it was shown that acetate as the major carbon source in a laboratory-scale reactor selected for denitrifiers with nonflocculating proper...

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Metabolic Profiles and Genetic Diversity of Denitrifying Communities in Activated Sludge after Addition of Methanol or Ethanol

Hallin

Throbäck

Dicksved

et al. 2006

Appl Environ Microbiol

102

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“…Issacs et al [6] reported that the denitrification rate could be significantly increased by supplementing an external carbon source to the anoxic reactor. Eng.…”

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confidence: 99%

Test of Porous Ceramic Material for the Immobilisation of Predominant Nitrifying Bacteria and for the Improvement of the AAO Process

Lee

Choi

Wiesmann³

2004

Engineering in Life Sciences

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The efficiency of nitrification in a fixed bed reactor was compared to that found in an activated sludge reactor to determine their sensitivity to changing loads and lower temperatures. Two structurally identical lab-scale systems, using the anaerobic/anoxic/ aerobic (AAO) process to remove nitrogen and phosphorus simultaneously, were operated in parallel with secondary clarifiers and sludge return. The first aerobic system was operated as an activated sludge reactor, the second system as a fixed bed reactor. 3± -P were achieved for both systems. However, the system with an aerobic fixed bed reactor was characterised by the following advantages over the system with an activated sludge reactor: a shorter time to reach almost complete nitrification, a higher nitrification rate at higher loads of NH 4 + -N and a lower sensitivity of nitrification at lower temperatures down to 12 C.

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“…The external carbon addition has the role of providing sufficient VFA into the system to enhance the production of PHA and therefore improve P removal. Several external carbon sources have been studied to balance the COD deficiency in wastewaters (Gerber et al, 1986;Jones, et al, 1987;Winter, 1989;Appeldoorm, et al, 1992;Isaacs et al, 1994;Hallin. et al, 1996;Guerrero et al, 2012;Tayà et al, 2012).…”

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confidence: 99%

Development and economic assessment of different WWTP control strategies for optimal simultaneous removal of carbon, nitrogen and phosphorus

Ostace

Baeza

Guerrero

et al. 2013

Computers & Chemical Engineering

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This paper presents the comparison of four control strategies for the A 2 /O WWTP configuration for simultaneous C, N and P removal. The control strategies: i) external COD-P control; ii) external recycle flow-P control; iii) nitrate control in the last anoxic reactor; iv) ammonia control in the last aerobic reactor, were combined with other common control loops to build different control structures and were simulated in Matlab/Simulink under different influent conditions. A systematic approach was conducted with all the strategies to assess their potential effectiveness, according to the following steps: theoretical design, setpoint optimization and, finally, a detailed comparison of the control results against a reference operation and an optimized reference scenario. The optimization of the reference operation presented a 7 % reduction of the total operational cost. The simulation results showed that some control strategies further reduced 3-7.5% the WWTP operational costs while the effluent quality is greatly improved.

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External carbon source addition as a means to control an activated sludge nutrient removal process

Cited by 72 publications

References 6 publications

Metabolic Profiles and Genetic Diversity of Denitrifying Communities in Activated Sludge after Addition of Methanol or Ethanol

Metabolic Profiles and Genetic Diversity of Denitrifying Communities in Activated Sludge after Addition of Methanol or Ethanol

Test of Porous Ceramic Material for the Immobilisation of Predominant Nitrifying Bacteria and for the Improvement of the AAO Process

Development and economic assessment of different WWTP control strategies for optimal simultaneous removal of carbon, nitrogen and phosphorus

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