Limitations of thermophilic anaerobic wastewater treatment and the consequences for process design.
01 Jan 1996-Antonie Van Leeuwenhoek International Journal of General and Molecular Microbiology (Antonie Van Leeuwenhoek)-Vol. 69, Iss: 1, pp 1-14
TL;DR: In this article, the process stability of thermophilic anaerobic wastewater treatment systems is investigated and a relatively low sensitivity to temperature changes if high-rate reactors with immobilized biomass are used.
Abstract: Thermophilic anaerobic digestion offers an attractive alternative for the treatment of medium- and high-strength wastewaters. However, literature reports reveal that thermophilic wastewater treatment systems are often more sensitive to environmental changes than the well-defined high-rate reactors at the mesophilic temperature range. Also, in many cases a poorer effluent quality is experienced while the carry over of suspended solids in the effluent is relatively high. In this paper recent achievements are discussed regarding the process stability of thermophilic anaerobic wastewater treatment systems. Laboratory experiments reveal a relatively low sensitivity to temperature changes if high-rate reactors with immobilized biomass are used. Other results show that if a staged process is applied, thermophilic reactors can be operated for prolonged periods of time under extreme loading conditions (80-100 kg chemical oxygen demand.m-3.day-1), while the concentrations of volatile fatty acids in the effluent remain at a low level.
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TL;DR: The aim of this paper is primarily to review the recent literature about the occurrence of both acetotrophic and hydrogenotrophic methanogens during anaerobic conversion of particulate biomass to methane (not wastewater treatment), while this review does not cover the activity of the acetate oxidizing bacteria.
Abstract: Among different conversion processes for biomass, biological anaerobic digestion is one of the most economic ways to produce biogas from various biomass substrates In addition to hydrolysis of polymeric substances, the activity and performance of the methanogenic bacteria is of paramount importance during methanogenesis The aim of this paper is primarily to review the recent literature about the occurrence of both acetotrophic and hydrogenotrophic methanogens during anaerobic conversion of particulate biomass to methane (not wastewater treatment), while this review does not cover the activity of the acetate oxidizing bacteria Both acetotrophic and hydrogenotrophic methanogens are essential for the last step of methanogenesis, but the reports about their roles during this phase of the process are very limited Despite, some conclusions can still be drawn At low concentrations of acetate, normally filamentous Methanosaeta species dominate, eg, often observed in sewage sludge Apparently, high concentrations of toxic ionic agents, like ammonia, hydrogen sulfide (H2S) and volatile fatty acids (VFA), inhibit preferably Methanosaetaceae and especially allow the growth of Methanosarcina species consisting of irregular cell clumps, eg, in cattle manure Thermophilic conditions can favour rod like or coccoid hydrogenotrophic methanogens Thermophilic Methanosarcina species were also observed, but not thermophilic Methanosaetae Other environmental factors could favour hydrogentrophic bacteria, eg, short or low retention times in a biomass reactor However, no general rules regarding process parameters could be derivated at the moment, which favours hydrogenotrophic methanogens Presumably, it depends only on the hydrogen concentration, which is generally not mentioned in the literature
1,018 citations
Cites background from "Limitations of thermophilic anaerob..."
...Additionally, a summary of the kinetic data for several methane forming bacteria are given in Table 4. More information for kinetic parameters of acetate and hydrogen utilizing methanogens can also be found elsewhere (Koster and Koomen 1988; Van Lier 1996 )....
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TL;DR: This mini-review of several fermentation processes is discussed, starting with the most advanced process of ethanol production, followed by methane production, an established process for waste water purification which is gaining more attention because of the inherent energy production.
Abstract: Because biomass is a widely available, renewable resource, its utilisation for the production of energy has great potential for reducing CO2 emissions and thereby preventing global warming. In this mini-review the `state of the art' of several fermentation processes is discussed, starting with the most advanced process of ethanol production. This is followed by methane production, an established process for waste water purification which is gaining more attention because of the inherent energy production. Subsequently ABE fermentation is discussed and finally the biological production of hydrogen. The last section proposes a new way to assess and compare the different processes by relating their merit to `work content' values and `lost work' instead of the combustion values of their products. It is argued that, especially when dealing with energy from biomass, the application of this methodology will provide a uniform valuation for different processes and products. The described fermentation processes enable the supply of pure energy carriers, either gaseous or liquid, from biomass, yet the introduction of these processes is hampered by two major problems. The first is related to technological shortcomings in the mobilisation of fermentable components from the biomass. The second, having a much greater impact, is linked with socio-economics: until full externality costs are attributed to fossil fuels, accounting for their role in pollution and global warming, the competitiveness of the processes described here will hardly stand a chance.
616 citations
TL;DR: The higher performances on the volatile solid and pathogen reduction, and stable operation of the temperature co-phase anaerobic system might be attributable to the well-functioned thermophilic digester, sharing nutrients and intermediates for anaerilic microorganisms, and selection of higher substrate affinity an aerobic microorganisms in the co- phase system.
341 citations
TL;DR: The microbial diversity of two types of methanogenic granular sludge, mesophilic and thermophilic, which had been treating sucrose/propionate/acetate-based artificial wastewater were compared, suggesting that the microbial Diversity of the thermophobic granule was lower than that of the Mesophilic granule.
Abstract: The microbial diversity of two types of methanogenic granular sludge, mesophilic (35 °C) and thermophilic (55 °C), which had been treating sucrose/propionate/acetate-based artificial wastewater were compared. 16S rDNA clone libraries were constructed by PCR with a prokaryote-specific primer set, and partial sequencing of the clonal 16S rDNAs was conducted for phylogenetic analysis. Of 115 mesophilic granule and 110 thermophilic granule clones sequenced, 19 and 22%, respectively, were phylogenetically affiliated with the domain Archaea, and the remainder in each case were assigned to the domain Bacteria. Within the domain Archaea, the 16S rDNA clones in both libraries showed relatively close relationships with those of methanogens. Within the Bacteria, a major group represented in the mesophilic clone library was the delta subclass of the Proteobacteria (27%), in which high degrees of relatedness were observed between the clonal 16S rDNA sequences and those of previously identified syntrophic bacteria and sulfate-reducing bacteria. In contrast, in the thermophilic clone library, the Thermodesulfovibrio group (19%), the green non-sulfur bacteria (18%) and the low G+C subclass of the Gram-positive bacteria (18%) were predominant. A significant difference between the two libraries was that no clone affiliated with the Proteobacteria was detected in the thermophilic clone library, whereas the Proteobacteria was the most predominant group in the mesophilic clones. Thirty-six and 24 different sequences were found in the mesophilic and thermophilic clones, respectively, suggesting that the microbial diversity of the thermophilic granule was lower than that of the mesophilic granule.
338 citations
TL;DR: Recent findings on the ecological significance and possible ecophysiological roles of 'Chloroflexi subphylum I' are discussed based on findings from both the characteristics of the cultured Chlor oflexi and molecular-based analyses.
Abstract: Cultivation-independent molecular surveys have shown members of the bacterial phylum Chloroflexi to be ubiquitous in various natural and artificial ecosystems. Among the subphylum-level taxa of the Chloroflexi known to date, the formerly uncultured 'subphylum I' had well been recognized as a typical group that contains a number of environmental gene clones with no culture representatives. In order to reveal their ecophysiology, attempts were made over the past decade to domesticate them into laboratory cultures, and significant advances have been made in cultivating strains belonging to the group. The microorganisms characterized so far include seven species in six genera, i.e., Anaerolinea, Levilinea, Leptolinea, Bellilinea, Longilinea, and Caldilinea, and were proposed to represent two classes, Anaerolineae and Caldilineae, providing solid insights into the phenotypic and genetic properties common to the group. Another subphylum-level uncultured group of the Chloroflexi, i.e., the class Ktedonobacteria, has also been represented recently by a cultured strain. In addition to the results from these tangible cultures, data obtained from functional analyses of uncultured Chloroflexi populations by assessing substrate uptake patterns are accumulating at an encouraging rate. In this review, recent findings on the ecological significance and possible ecophysiological roles of 'Chloroflexi subphylum I' are discussed based on findings from both the characteristics of the cultured Chloroflexi and molecular-based analyses.
235 citations
References
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Book•
01 Oct 2007
TL;DR: In this paper, conversion factors and mathematical symbols are used to describe conversion factors in physical and chemical data and Mathematical Symbols are used for converting, converting, and utilising conversion factors.
Abstract: Section 1: Conversion Factors and Mathematical Symbols Section 2: Physical and Chemical Data Section 3: Mathematics Section 4: Thermodynamics Section 5: Heat and Mass Transfer Section 6: Fluid and Plastic Dynamics Section 7: Reaction Kinetics Section 8: Process Control Section 9: Process Economics Section 10: Transport and Storage of Fluids Section 11: Heat-Transfer Equipment Section 12: Psychrometry, Evaporative Cooling, and Solids Drying Section 13: Distillation Section 14: Equipment for Distillation, Gas Absorption, Phase Dispersion, and Phase Separation Section 15: Liquid-Liquid Extraction and Other Liquid-Liquid Operations and Equipment Section 16: Adsorption and Ion Exchange Section 17: Gas-Solid Operations and Equipment Section 18: Liquid-Solid Operations and Equipment Section 19: Reactors Section 20: Alternative Separation Processes Section 21: Solid-Solid Operations and Processing Section 22: Waste Management Section 23: Process Safety Section 24: Energy Resources, Conversion, and Utilization Section 25: Materials of Construction Index
10,028 citations
Book•
01 Jan 1980
TL;DR: In this paper, chemical engineering kinetics was studied in terms of kinetics in the context of Chemical Engineering kinetics and its application in the field of chemical engineering. But they did not discuss the application of the kinetics of protein kinetics.
Abstract: Chemical engineering kinetics , Chemical engineering kinetics , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی
1,506 citations
"Limitations of thermophilic anaerob..." refers background in this paper
...Therefore, immobilization of bacteria in biofilms and/or granules, may enhance the thermostability of the process due to the fact that the maximum conversion rate will be determined by diffusion limitation of the substrate (Smith 1981 ; Lens et al. 1993; Pavlostathis & Giraldo-Gomez 1991)....
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TL;DR: The fundamentals of microbial kinetics and continuous culture models are presented and the effect of temperature and inhibitors on the intrinsic kinetic rates is discussed, and Stoichiometric and bioenergetic considerations are reviewed.
Abstract: The fundamentals of microbial kinetics and continuous culture models are presented. The kinetics of the anaerobic treatment processes are reviewed recognizing that anaerobic degradation of complex, polymeric organic materials is a combination of series and parallel reactions. Such reactions include hydrolysis, fermentation, anaerobic oxidation of fatty acids, and methanogenesis. The intrinsic rates of each step are reviewed and literature data summarized. Whenever possible, available kinetic information is summarized on the basis of substrate composition (such as carbohydrates, proteins, and lipids). The effect of temperature and inhibitors on the intrinsic kinetic rates is discussed. Stoichiometric and bioenergetic considerations are reviewed. Mass transfer limitations (both external and internal) associated with biofilms and microbial agglomerates, in general, and their effect on the intrinsic kinetic rates are presented. Areas requiring further research are identified.
638 citations
TL;DR: A methanogenic bacterium, commonly seen in digested sludge and referred to as the “fat rod” or Methanobacterium soehngenii, has been enriched to a monoculture and is characterized.
Abstract: A methanogenic bacterium, commonly seen in digested sludge and referred to as the "fat rod" or Methanobacterium soehngenii, has been enriched to a monoculture and is characterized. Cells are gramnegative, non-motile and appear as straight rods with flat ends. They form filaments which can grow to great lengths. The structure of the outer cell envelop is similar to Methanospirillum hungatii. The organism grows on a mineral salt medium with acetate as the only organic component. Acetate is the energy source, and methane is formed exclusively from the methyl group. Acetate and carbon dioxide act as sole carbon source and are assimilated in a molar ratio of about 1.9:1. The reducing equivalents necessary to build biomass from these two precursors are obtained from the total oxidation of some acetate. Hydrogen is not used for methane formation and is not needed for growth. Formate is cleaved into hydrogen and carbon dioxide. Coenzyme M was found to be present at levels of 0.35 nmol per mg of dry cells and F420 amounted to 0.55 microgram per mg protein. The mean generation time was 9 days at 33 degrees C.
512 citations
TL;DR: In this paper, the effect of temperature in the range of 40-64°C on thermophilic anaerobic digestion of cattle manure with two different ammonia concentrations (2.5 and 6.0 g-N/l) was investigated in continuouslyfed lab-scale reactors: the higher ammonia concentration reduced the maximum tolerable temperature.
455 citations