A comparison between exogenous carriers enhanced aerobic granulation under low organic loading in the aspect of sludge characteristics, extracellular polymeric substances and microbial communities

2021 ◽  
pp. 126567
Author(s):  
Zhe Liu ◽  
Xuhua Zhang ◽  
Shumin Zhang ◽  
Hao Qi ◽  
Yiwen Hou ◽  
...  
Keyword(s):  
Microbial Communities ◽  
Extracellular Polymeric Substances ◽  
Organic Loading ◽  
Aerobic Granulation ◽  
Sludge Characteristics

Community structure of micro- and macroflocs in pin-point sludge and the influence of sludge age and potassium addition on microfloc formation

2002 ◽  
Vol 46 (1-2) ◽  
pp. 405-412 ◽  
Author(s):  
E. Müller ◽  
K. Kriebitzsch ◽  
P.A. Wilderer ◽  
S. Wuertz
Keyword(s):  
Community Structure ◽  
Microbial Communities ◽  
Extracellular Polymeric Substances ◽  
Point Of View ◽  
Sludge Formation ◽  
Industrial Plants ◽  
Noticeable Improvement ◽  
Lower Protein ◽  
Utilization Patterns ◽  
The Impact

Settling problems caused by pin-point sludge constitute a serious problem in biological wastewater treatment, particularly in many industrial plants. Until now, most studies focused on the relationship between pin-point sludge formation and either shearing forces or the impact of toxicants. This study deals with the community structure in both the micro- and macrofloc fraction which was analyzed by fluorescent in situ hybridization (FISH) and BIOLOG substrate utilization patterns. It was shown that each fraction consisted of different microbial communities with unique metabolic profiles suggesting that pin-point sludge formation is not due to dispersal of intact flocs but to microcolonies growing separately. Alternatively, macroflocs may have an architecture leading to segregation of microbial communities after floc dispersal. Further it could be shown that the formation of microflocs was influenced by sludge age. The best sludge sedimentation was obtained for a sludge age of 5 and 10 days. Additional analysis of extracellular polymeric substances (EPS) suggested that the lower protein to carbohydrate ratio of 10-day-old sludge led to better flocculation compared to 20-day-old sludge containing similar total amounts of EPS. From a practical point of view, addition of potassium (0.1 g/l) effected a noticeable improvement of sludge settleability.

Granulation of biological flocs under elevated pressure: characteristics of granules

2013 ◽  
Vol 67 (12) ◽  
pp. 2850-2855
Author(s):  
Yang-Min Liang ◽  
Jie-Yuan Chen ◽  
Gaëtan Marchesini ◽  
Chi-Wang Li ◽  
Shiao-Shing Chen
Keyword(s):  
Extracellular Polymeric Substances ◽  
Loading Rate ◽  
Ambient Pressure ◽  
Elevated Pressure ◽  
Volume Index ◽  
Organic Loading Rate ◽  
Organic Loading ◽  
Oxygen Penetration ◽  
Long Term Stability

Aerobic granules (AG) have good settling ability and are relatively insensitive to the variation of organic loading rate. When sizes of granules become bigger, substrate and oxygen become limited in the granule core, leading to cell lysis and disintegration of granules. The higher the dissolved oxygen, the deeper the oxygen penetration inside AG. AG operated under elevated pressure might be a possible way to maintain long-term stability of granules. In this study, formation and characteristics of AG in the reactor operated under elevated high pressure (HP) and ambient pressure (AP) are investigated. Results show that both systems removed an average 95% of total organic carbon. Sludge volume index at 5 and 30 min settling times under HP are 35% smaller those under AP, indicating that HP granules have a better settling ability and a denser structure than AP granules. The granule size in the HP system is very uniform, while size distribution in the AP system is broader, indicating that the AP system contains flocculent sludge. Extracellular polymeric substances and polysaccharides (PS) are almost the same for HP and AP; however, exopolymeric protein (PN) is very different. PS/PN ratio for HP sludge is four times that of AP. The result is consistent with sludge settleability, which is improved with increasing PS/PN ratio.

scholarly journals Spatio-temporal modeling of the crowding conditions and metabolic variability in microbial communities

2021 ◽  
Vol 17 (7) ◽  
pp. e1009140
Author(s):  
Liliana Angeles-Martinez ◽  
Vassily Hatzimanikatis
Keyword(s):  
Microbial Communities ◽  
Extracellular Polymeric Substances ◽  
Resource Competition ◽  
Local Environment ◽  
Microbial Interactions ◽  
Relative Fitness ◽  
Flux Analysis ◽  
Scaled Particle Theory ◽  
Spatio Temporal ◽  
The Impact

The metabolic capabilities of the species and the local environment shape the microbial interactions in a community either through the exchange of metabolic products or the competition for the resources. Cells are often arranged in close proximity to each other, creating a crowded environment that unevenly reduce the diffusion of nutrients. Herein, we investigated how the crowding conditions and metabolic variability among cells shape the dynamics of microbial communities. For this, we developed CROMICS, a spatio-temporal framework that combines techniques such as individual-based modeling, scaled particle theory, and thermodynamic flux analysis to explicitly incorporate the cell metabolism and the impact of the presence of macromolecular components on the nutrients diffusion. This framework was used to study two archetypical microbial communities (i) Escherichia coli and Salmonella enterica that cooperate with each other by exchanging metabolites, and (ii) two E. coli with different production level of extracellular polymeric substances (EPS) that compete for the same nutrients. In the mutualistic community, our results demonstrate that crowding enhanced the fitness of cooperative mutants by reducing the leakage of metabolites from the region where they are produced, avoiding the resource competition with non-cooperative cells. Moreover, we also show that E. coli EPS-secreting mutants won the competition against the non-secreting cells by creating less dense structures (i.e. increasing the spacing among the cells) that allow mutants to expand and reach regions closer to the nutrient supply point. A modest enhancement of the relative fitness of EPS-secreting cells over the non-secreting ones were found when the crowding effect was taken into account in the simulations. The emergence of cell-cell interactions and the intracellular conflicts arising from the trade-off between growth and the secretion of metabolites or EPS could provide a local competitive advantage to one species, either by supplying more cross-feeding metabolites or by creating a less dense neighborhood.

scholarly journals The influence of microbial mats on travertine precipitation in active hydrothermal systems (Central Italy)

2020 ◽  
Author(s):  
Giovanna Della Porta ◽  
Joachim Reitner
Keyword(s):  
Microbial Communities ◽  
Extracellular Polymeric Substances ◽  
Microbial Mats ◽  
Central Italy ◽  
Hydrothermal Systems ◽  
Crystal Nucleation ◽  
Anoxygenic Phototrophic Bacteria ◽  
Physico Chemical ◽  
Slope System ◽  
Aluminium Silicates

ABSTRACTThe study of hydrothermal travertines contributes to the understanding of the interaction between physico-chemical processes and the role played by microbial mats and biofilms in influencing carbonate precipitation. Three active travertine sites were investigated in Central Italy to identify the types of carbonate precipitates and the associated microbial mats at varying physico-chemical parameters. Carbonate precipitated fabrics at the decimetre- to millimetre-scale and microbial mats vary with decreasing water temperature: a) at high temperature (55-44°C) calcite or aragonite crystals precipitate on microbial mats of sulphide oxidizing, sulphate reducing and anoxygenic phototrophic bacteria forming filamentous streamer fabrics, b) at intermediate temperature (44-40°C), rafts, coated gas bubbles and dendrites are associated with Spirulina cyanobacteria and other filamentous and rod-shaped cyanobacteria, c) low temperature (34-33°C) laminated crusts and oncoids in a terraced slope system are associated with diverse Oscillatoriales and Nostocales filamentous cyanobacteria, sparse Spirulina and diatoms. At the microscale, carbonate precipitates are similar in the three sites consisting of prismatic calcite (40-100 μm long, 20-40 μm wide) or acicular aragonite crystals organized in radial spherulites, overlying or embedded within biofilm EPS (Extracellular Polymeric Substances). Microsparite and sparite crystal size decreases with decreasing temperature and clotted peloidal micrite dominates at temperatures < 40°C, also encrusting filamentous microbes. Carbonates are associated with gypsum and Ca-phosphate crystals; EPS elemental composition is enriched in Si, Al, Mg, Ca, P, S and authigenic aluminium-silicates form aggregates on EPS.This study confirms that microbial communities in hydrothermal travertine settings vary as a function of temperature. Carbonate precipitate types at the microscale do not vary considerably, despite different microbial communities suggesting that travertine precipitation, driven by CO2 degassing, is influenced by biofilm EPS acting as template for crystal nucleation (EPS-mediated mineralization) and affecting the fabric types, independently from specific microbial metabolism.

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