scholarly journals The environment selects: Modeling energy allocation in microbial communities under dynamic environments

2019 ◽  
Author(s):  
Leonor Guedes da Silva ◽  
Sergio Tomás-Martínez ◽  
Mark C.M. van Loosdrecht ◽  
S. Aljoscha Wahl
Keyword(s):  
Growth Yield ◽  
Selective Advantage ◽  
Energy Allocation ◽  
Metabolic Function ◽  
Biological Phosphorus Removal ◽  
Trade Offs ◽  
Polyphosphate Accumulating Organisms ◽  
Modeling Formalism ◽  
The Impact ◽  
Biological Phosphorus

ABSTRACTWhat will be the best metabolic strategy in a competitive environment where oxygen is periodically unavailable? A few decades ago, an accidental, man-made cyclic anaerobic/aerobic environment selected for Polyphosphate Accumulating Organisms (PAOs) and this strategy is now widely used to allow for Enhanced Biological Phosphorus Removal (EBPR) of wastewater. But could it have been predicted? Here, a dynamic resource allocation modeling formalism was used to analyze the impact of selection pressures on metabolic function. With the same meta-network but modified selective pressures, different successful strategies can be predicted: Polyphosphate-AOs, Glycogen-AOs, Polyhydroxyalkanoate-AOs, and regular aerobic heterotrophs. The results demonstrate how storage metabolism allows for different trade-offs between growth yield, robustness, and competitiveness, and highlight how each metabolic function is an important determining factor for a selective advantage in a given environment. This can be seen as an example of when “Unity in biochemistry” by A.Kluyver meets “Everything is everywhere, but the environment selects” by B.Becking and how microbial ecosystems may be described by the energy allocation phenotype instead of a detailed description of each organism.

Heterotrophic Kinetic Parameter Estimation for Enhanced Biological Phosphorus Removal Processes Operated in Conventional and Membrane-Assisted Modes

2006 ◽  
Vol 41 (1) ◽  
pp. 72-83 ◽  
Author(s):  
Zhe Zhang ◽  
Eric R. Hall
Keyword(s):  
Parameter Estimation ◽  
Phosphorus Removal ◽  
Growth Yield ◽  
Pilot Scale ◽  
Enhanced Biological Phosphorus Removal ◽  
Biological Phosphorus Removal ◽  
Nitrogen And Phosphorus ◽  
Parameter Values ◽  
The Impact ◽  
Biological Phosphorus

Abstract Parameter estimation and wastewater characterization are crucial for modelling of the membrane enhanced biological phosphorus removal (MEBPR) process. Prior to determining the values of a subset of kinetic and stoichiometric parameters used in ASM No. 2 (ASM2), the carbon, nitrogen and phosphorus fractions of influent wastewater at the University of British Columbia (UBC) pilot plant were characterized. It was found that the UBC wastewater contained fractions of volatile acids (SA), readily fermentable biodegradable COD (SF) and slowly biodegradable COD (XS) that fell within the ASM2 default value ranges. The contents of soluble inert COD (SI) and particulate inert COD (XI) were somewhat higher than ASM2 default values. Mixed liquor samples from pilot-scale MEBPR and conventional enhanced biological phosphorus removal (CEBPR) processes operated under parallel conditions, were then analyzed experimentally to assess the impact of operation in a membrane-assisted mode on the growth yield (YH), decay coefficient (bH) and maximum specific growth rate of heterotrophic biomass (µH). The resulting values for YH, bH and µH were slightly lower for the MEBPR train than for the CEBPR train, but the differences were not statistically significant. It is suggested that MEBPR simulation using ASM2 could be accomplished satisfactorily using parameter values determined for a conventional biological phosphorus removal process, if MEBPR parameter values are not available.

Short-term effects of carbon source on the competition of polyphosphate accumulating organisms and glycogen accumulating organisms

2004 ◽  
Vol 50 (10) ◽  
pp. 139-144 ◽  
Author(s):  
A. Oehmen ◽  
Z. Yuan ◽  
L.L. Blackall ◽  
J. Keller
Keyword(s):  
Carbon Source ◽  
In Situ Hybridisation ◽  
Operating Conditions ◽  
Fluorescence In Situ Hybridisation ◽  
Biological Phosphorus Removal ◽  
Short Term ◽  
Uptake Rates ◽  
Polyphosphate Accumulating Organisms ◽  
The Impact ◽  
Short Term Effects

The effectiveness of enhanced biological phosphorus removal (EBPR) systems is directly affected by the competition of polyphosphate accumulating organisms (PAOs) and glycogen accumulating organisms (GAOs). This study investigated the short-term effects of carbon source on PAO and GAO performance. The tests were designed to clearly determine the impact of volatile fatty acid (VFA) composition on the performance of two types of biomass, one enriched for PAOs and the other for GAOs. The two populations were enriched in separate reactors using identical operating conditions and very similar influent compositions with acetate as the sole carbon source. The only difference was that a very low level of phosphorus was present in the influent to the GAO reactor. The abundance of PAOs and GAOs was quantified using fluorescence in-situ hybridisation. The results clearly show that there are some very distinctive differences between PAOs and GAOs in their ability to utilise different carbon substrates. While both are able to take up acetate rapidly and completely, the GAOs are far slower at consuming propionate than the PAOs during short-term substrate changes. This provides a potentially highly valuable avenue to influence the competition between PAOs and GAOs. Other VFAs studied seem to be less usable in the short term by both PAOs and GAOs, as indicated by their much lower uptake rates.

Distributed microbial state effects on competitionin enhanced biological phosphorus removal systems

2006 ◽  
Vol 54 (1) ◽  
pp. 199-207 ◽  
Author(s):  
A.J. Schuler
Keyword(s):  
Phosphorus Removal ◽  
Enhanced Biological Phosphorus Removal ◽  
Biological Phosphorus Removal ◽  
Storage Product ◽  
Distributed Approach ◽  
Average System ◽  
Storage Products ◽  
Profile Characteristics ◽  
Polyphosphate Accumulating Organisms ◽  
Biological Phosphorus

Computer simulation of activated sludge population dynamics is a useful tool in process design, operation, and troubleshooting, but currently available programs rely on the assumption of “lumped,” or average, system characteristics in each reactor, such as microbial storage product contents. In reality, the states of individual bacteria are likely to vary due to variable residence times in reactors with completely mixed hydraulics. Earlier work by the present author introduced the MATLAB-based distributed state simulation program, Dissimulator 1.0, and demonstrated that distributed states may be particularly important in enhanced biological phosphorus removal (EBPR) systems, which rely on the cycling of bacteria through anaerobic and aerobic reactors to select for a population accumulating multiple microbial storage products. This paper explores the relationships between distributed state profiles, variable anaerobic and aerobic SRTs, and the process rates predicted by lumped and distributed approaches. Consistent with previous results, the lumped approach consistently predicted better EBPR performance than did the distributed approach. The primary reason for this was the presence of large fractions of polyphosphate accumulating organisms (PAOs) with depleted microbial storage product contents, which led to overestimation of process rates by the lumped approach. Distributed and lumped predictions were therefore most similar when microbial storage product depletion was minimal. The effects of variable anaerobic and aerobic SRTs on distributed profile characteristics and process rates are presented. This work demonstrated that lumped assumptions may overestimate EBPR performance, and the degree of this error is a function of the distributed state profile characteristics such as the degree to which fractions of the biomass contain depleted microbial storage product contents.

Uncertainty and variability in enhanced biological phosphorus removal (EBPR) stoichiometry: consequences for process modelling and optimization

2010 ◽  
Vol 61 (7) ◽  
pp. 1793-1800 ◽  
Author(s):  
Dwight Houweling ◽  
Yves Comeau ◽  
Imre Takács ◽  
Peter Dold
Keyword(s):  
Phosphorus Removal ◽  
Volatile Fatty Acids ◽  
Enhanced Biological Phosphorus Removal ◽  
Biological Phosphorus Removal ◽  
Feed Composition ◽  
P Limitation ◽  
Polyphosphate Accumulating Organisms ◽  
Biological Phosphorus ◽  
P Removal

The overall potential for enhanced biological phosphorus removal (EBPR) in the activated sludge process is constrained by the availability of volatile fatty acids (VFAs). The efficiency with which polyphosphate accumulating organisms (PAOs) use these VFAs for P-removal, however, is determined by the stoichiometric ratios governing their anaerobic and aerobic metabolism. While changes in anaerobic stoichiometry due to environmental conditions do affect EBPR performance to a certain degree, model-based analyses indicate that variability in aerobic stoichiometry has the greatest impact. Long-term deterioration in EBPR performance in an experimental SBR system undergoing P-limitation can be predicted as the consequence of competition between PAOs and GAOs. However, the observed rapid decrease in P-release after the change in feed composition is not consistent with a gradual shift in population.

Comparison of nutrient removal efficiency between pre- and post-denitrification wastewater treatments

2006 ◽  
Vol 53 (9) ◽  
pp. 169-175 ◽  
Author(s):  
K. Hamada ◽  
T. Kuba ◽  
V. Torrico ◽  
M. Okazaki ◽  
T. Kusuda
Keyword(s):  
Nutrient Removal ◽  
Phosphorus Removal ◽  
Biological Nutrient Removal ◽  
Biological Phosphorus Removal ◽  
Nitrogen And Phosphorus ◽  
Nitrogen And Phosphorus Removal ◽  
Nutrient Removal Efficiency ◽  
Polyphosphate Accumulating Organisms ◽  
Biological Phosphorus ◽  
Denitrification Process

A shortage of organic substances (COD) may cause problems for biological nutrient removal, that is, lower influent COD concentration leads to lower nutrient removal rates. Biological phosphorus removal and denitrification are reactions in which COD is indispensable. As for biological simultaneous nitrogen and phosphorus removal systems, a competition problem of COD utilisation between polyphosphate accumulating organisms (PAOs) and non-polyphosphate-accumulating denitrifiers is not avoided. From the viewpoint of effective utilisation of limited influent COD, denitrifying phosphorus-removing organisms (DN-PAOs) can be effective. In this study, DN-PAOs activities in modified UCT (pre-denitrification process) and DEPHANOX (post-denitrification ptocess) wastewater treatments were compared. In conclusion, the post-denitrification systems can use influent COD more effectively and have higher nutrient removal efficiencies than the conventional pre-denitrification systems.

Presence of Rhodocyclus in a full-scale wastewater treatment plant and their participation in enhanced biological phosphorus removal

2002 ◽  
Vol 46 (1-2) ◽  
pp. 123-128 ◽  
Author(s):  
J.L. Zilles ◽  
C.-H. Hung ◽  
D.R. Noguera
Keyword(s):  
Wastewater Treatment ◽  
Phosphorus Removal ◽  
Fluorescent In Situ Hybridization ◽  
Wastewater Treatment Plants ◽  
Full Scale ◽  
Enhanced Biological Phosphorus Removal ◽  
Biological Phosphorus Removal ◽  
Polyphosphate Accumulating Organisms ◽  
Biological Phosphorus

The objective of this research was to assess the relevance of organisms related to Rhodocyclus in enhanced biological phosphorus removal in full-scale wastewater treatment plants. The presence of these organisms in full-scale plants was first confirmed by fluorescent in situ hybridization. To address which organisms were involved in phosphorus removal, a method was developed which selected polyphosphate-accumulating organisms from activated sludge samples by DAPI staining and flow cytometry. Sorted samples were characterized using fluorescent in situ hybridization. The results of these analyses confirmed the presence of organisms related to Rhodocyclus in full-scale wastewater treatment plants and supported the involvement of these organisms in enhanced biological phosphorus removal. However, a significant fraction of the polyphosphate-accumulating organisms were not related to Rhodocyclus.

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