Characterization of anaerobic granular sludge developed in UASB reactors that treat ethanol, carbohydrates and hydrolyzed protein based wastewaters (original) (raw)
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Microbial characteristics of methanogenic sludge consortia developed in thermophilic U ASB reactors
Applied Microbiology and Biotechnology, 1993
The effect of temperature on granulation and microbial interaction of anaerobic sludges grown in thermophilic upflow anaerobic sludge bed (UASB) reactors was investigated at two different temperatures, 55°C (Run 1) and 65°C (Run 2). Each run consisted of two phases. Phase 1 was conducted by feeding acetate for a period of 200 days. In Phase 2, both reactors were fed a mixture of acetate and sucrose for a further 100 days. During Phase 1, no granulation occurred in the sludge of either run. Microscopic observation revealed that the predominant methanogen was Methanothrix in Run 1, whereas Methanobacterium-like bacteria existed to a significant extent in Run 2. The acetate-utilizing methanogenic activity of both sludges increased with increasing test temperature in the range 55–65°C. Since the acetate-grown sludges exhibited far higher H2-utilizing methanogenic activity than acetate-utilizing methanogenic activity, it is suggested that a syntrophic association of acetate-oxidizing bacteria with hydrogenotrophic methanogens was responsible for a considerable portion of the overall acetate elimination in thermophilic anaerobic sludge. During Phase 2, granules coated with either filamentous bacteria or cocci-type bacteria (both presumably acid-forming bacteria) were successfully established in Run 1 and Run 2, respectively. Since the acetate-utilizing methanogenic activities of the granular sludges were four to five times higher than those of the acetate-grown sludges (Phase 1), the co-existence of these “coating bacteria” appeared to contribute to the enclosing of acetate consumers inside granules.
Bacteriological composition and structure of granular sludge adapted to different substrates
Applied and environmental microbiology, 1991
The bacteriological composition and ultrastructure of mesophilic granular methanogenic sludge from a large-scale Upflow Anaerobic Sludge Blanket reactor treating wastewater from a sugar plant and of sludge granules adapted to ethanol and propionate were studied by counting different bacterial groups and by immunocytochemical methods. Propionate-grown granular sludge consisted of two types of clusters, those of a rod-shaped bacterium immunologically related to Methanothrix soehngenii and those consisting of two different types of bacteria with a specific spatial orientation. One of these bacteria reacted with antiserum against Methanobrevibacter arboriphilus AZ, whereas the other is most likely a propionate-oxidizing bacterium immunologically unrelated to Syntrophobacter wolinii. Sludge granules obtained from the large-scale Upflow Anaerobic Sludge Blanket reactor and granules cultivated on ethanol did not show the typical spatial orientation of bacteria. Examination of the bacterial...
Journal of Rapid Methods & Automation in Microbiology, 2009
Microorganisms were grown in the form of anaerobic granular sludge in two lab-scale Upflow Anaerobic Sludge Bed (UASB) reactors fed with synthetic wastewater and operated at psychrophilic and mesophilic temperature conditions. Since hydrogenotrophic and aceticlastic methanogenesis are known to play a crucial role, digestion may be effectively blocked if these processes are ceased due to unfavorable environmental temperature conditions. Mesophilic (35 Ϯ 2C) and psychrophilic (10 Ϯ 1C) reactors were inoculated by the same mesophilic granules taken from a full-scale UASB reactor. According to FISH results, Archaea representing methanogens were found dominating at bottom sampling ports of reactors and dominant member of Archaea was the genus aceticlastic Methanosaeta (MX825). Other aceticlastic methanogen such as Methanosarcina-like (SARCI645) species were also identified which were higher in psychrophilic granules. Members of order Methanobacteriales (MB310) constituted the major hydrogenothrophic methanogens in both reactors, whereas other hydrogenothrophic methanogens members of order Methanococcales (MC1109) and Methanogenium (MG1200) relatives were 3 Corresponding 135 absent. Abundance of originally mesophilic Methanosaeta-related Archaea under low temperature conditions demonstrated the adaptive capacity of microorganisms to psychrophilic conditions. This might be attributed to enzymatic alterations in Methanosaeta cells originating from seed sludge, which were exposed to sub-mesophilic temperatures at start-up and then to psychrophilic conditions during gradual temperature decreases. Both sludge granules remained undisturbed and kept their rigidity even after exposure to very low temperatures. Quantification study was done using Image Pro-plus Version 4.0. Archaeal cells detected with probe ARC915 were found around 60% of the 4,6-diamidino-2-phenylindole stained cells at both reactors. Methanosaeta spp./Archaea ratios for mesophilic and psychrophilic UASB reactors were calculated as 71% and 84%, respectively. FISH and CSLM results together with quantification study showed that the microbial community of anaerobic granular sludges was dominated by Methanosaeta spp. which was identified as the major methanogenic Archaea.
Applied and Environmental Microbiology, 1991
Granules from an upflow anaerobic sludge blanket system treating a brewery wastewater that contained mainly ethanol, propionate, and acetate as carbon sources and sulfate (0.6 to 1.0 mM) were characterized for their physical and chemical properties, metabolic performance on various substrates, and microbial composition. Transmission electron microscopic examination showed that at least three types of microcolonies existed inside the granules. One type consisted of Methanothrix-like rods with low levels of Methanobacterium-like rods; two other types appeared to be associations between syntrophic-like acetogens and Methanobacterium-like organisms. The granules were observed to be have numerous vents or channels on the surface that extended into the interior portions of the granules that may be involved in release of gas formed within the granules. The maximum substrate conversion rates (millimoles per gram of volatile suspended solids per day) at 35°C in the absence of sulfate were 45.1, 8.04, 4.14, and 5.75 for ethanol, acetate, propionate, and glucose, respectively. The maximum methane production rates (millimoles per gram of volatile suspended solids per day) from H2-CO2 and formate were essentially equal for intact granules (13.7 and 13.5) and for physically disrupted granules (42 and 37). During syntrophic ethanol conversion, both hydrogen and formate were formed by the granules. The concentrations of these two intermediates were maintained at a thermodynamic equilibrium, indicating that both are intermediate metabolites in degradation. Formate accumulated and was then consumed during methanogenesis from H2-C02. Higher concentrations of formate accumulated in the absence of sulfate than in the presence of sulfate. The addition of sulfate (8 to 9 mM) increased the maximum substrate degradation rates for propionate and ethanol by 27 and 12%, respectively. In the presence of this level of sulfate, sulfate-reducing bacteria did not play a significant role in the metabolism of H2, formate, and acetate, but ethanol and propionate were converted via sulfate reduction by approximately 28 and 60%, respectively. In the presence of 2.0 mM molybdate, syntrophic propionate and ethanol conversion by the granules was inhibited by 97 and 29%, respectively. The data show that in this granular microbial consortium, methanogens and sulfate-reducing bacteria did not compete for common substrates. Syntrophic propionate and ethanol conversion was likely performed primarily by sulfate-reducing bacteria, while H2, formate, and acetate were consumed primarily by methanogens. Methanogenic granules are self-immobilized consortia of methanogens, syntrophic acetogens, and hydrolytic-fermen-tative bacteria that convert soluble organic matter to methane and CO2. The published work on the granule formation, microbial composition, substrate conversion potentials, and microbial structures of granules has focused on methanogens and syntrophic acetogens (7-11, 15, 23, 32, 39). This is likely due to the observation that sulfate-reducing bacteria (SRB) are present at much lower levels than syntrophic acetogens in granules treating sugar wastewater (10). Considerable information as to the methanogenic degradation of acetate, formate, and H2-CO2 in granules has been reported (7, 8, 11). Little work, however, has been performed to evaluate the conversion of other common substrates such as ethanol, propionate, and butyrate. SRB are quite diverse in terms of metabolic activities, morphotypes, trophic properties, and substrate affinities. In the presence of sulfate, acetate can be oxidized to CO2 by some pure SRB cultures; propionate, butyrate, and other volatile fatty acids (VFAs) can be oxidized completely to * Corresponding author. CO2 or converted to acetate or acetate plus propionate (in the case of odd long-chain acids with five or more carbon atoms); branched fatty acids such as isobutyrate, isovaler-ate, and 2-methylbutyrate can also be oxidized completely to CO2 or incompletely to acetate (35, 37). Hydrogen and formate can be utilized by many SRB as electron donors for sulfate reduction (35). Acetate and methanol are degraded via sulfate reduction by a coculture consisting of Desulfo-vibrio vulgaris and Methanosarcina barkeri (22). Methanol can be also degraded to CO2 via sulfate reduction by a coculture consisting of Desulfovibrio vulgaris and various homoacetogens (6, 12). In the absence of sulfate, certain SRB such as Desulfovibrio spp. may grow together with H2-utilizing methanogens to convert ethanol or lactate to acetate syntrophically (18, 34). The existence of syntrophic associations between H2-producing SRB and H2-consuming methanogens in lake sediments was suggested (5). No mention of syntrophic catabolism of VFAs by SRB in granular systems has been reported. VFAs such as propionate and butyrate are thought to be converted only by obligate syntrophic acetogens in concert with H2-utilizing methano-gens (3, 19, 20, 28, 35). In this study, methanogenic granules grown on brewery 3438
Evolution of microbial activities and population in granular sludge from an UASB reactor
Biotechnology Letters, 1990
With granular sludges grown in an UASB reactor fed with a mixture of acetate and proplonate, it is shown that (I) growth of proplonate-utilizing bacteria is responsible for the increase of the VSS content of the granular sludge, acetoclastic microfiora did not grow or little, (II) there is not a stolchlometric relationship between substrate removal and observed methane production, and (III) contrary to the common practice the best way to present data on bacterial concentrations in sludges is: bacteria/g VSS, which will provide a reliable basis for comparisons between different works from various authors.
Applied Microbiology and Biotechnology, 1993
Two types of methanogenic gianules capable of high chemical oxygen demand removal rates were developed in laboratory-scale upflow reactors at 35 ° C. One granule type (R-granules) had a rod-type Metha-nothrix-like species as the predominant species whereas the other (F-granules) had a filament-type M. soehn-genii-like acetate-utilizer as the predominant species. These two types of granules were compared in terms of operational performance, physical-chemical characteristics and microbial population. The R-granules had a higher density [65-70 vs 39-43 g suspended solids (SS)/1], specific gravity (1.03 vs 1.01) and specific volu-metric methane production rate (180 vs 120 1 CH4/I granules per day) than the F-granules. Acetate, pro-pionate and butyrate degraders in both types of granules had similar specific growth rates. The most probable number enumeration indicated that both types of granule had the same population levels (cells/g SS) in terms of methanogens (H2-CO2-, formate-and acetate-utilizing), and syntrophie acetogens. Hydrolyticrfer-mentative bacteria were present in greater number in the F-granules than in the R-granules. The R-granules had a higher cell density than the F-granules. The differences in operational performance were due mainly to their different microbial composition, especially the predominant acetate-utilizing methanogens in the granules. The long-filamentous M. soehngenii-like rods in the F-granules appeared to be responsible for their lower density and large-sized granules.
Role of sludge volume index in anaerobic sludge granulation in a hybrid anaerobic reactor
Research Article- CHEMICAL ENGINEERING JOURNAL, 2016
Sludge Volume Index (SVI) Denaturing Gel Gradient Electrophoresis (DGGE) Quantitative Polymerase Chain Reaction (qPCR) Scanning Electron Microscopy (SEM) a b s t r a c t This work focuses on microbial granulation in hybrid anaerobic reactors (HAR). Five HARs were used in two sets of experiments and all were seeded with the same inoculum. The volume of inoculum added was 10%, 20%, 30%, 40% and 50% in the first and 13%, 15%, 18%, 23%, and 27% in the second set of experiment. The volume of inocula added affects the sludge volume index, which in the present study proves to be important parameter for granulation. The results suggest that if SVI during the reactor start-up is kept between 150 and 210, reactors were able to form granules. Outside this range in the present setup , no granulation was observed due to increased biomass wash-out, causing decreased SRT. Higher methane production was achieved in reactors with good granulation. The DGGE profiles show that the non-granulating systems had lesser diversity, due to increased wash out. Archaeal profile gave better correlation for granulation. Granulating reactors were rich in aceticlastic methanogens over hydrogen utilizing groups, especially Methanosaetaceae. Both Methanosarcina and Methanosaeta are required for better granulation as confirmed quantitatively. Bacterial profile of granulating reactors were rich in acetogens. SEM (Scanning electron microscopy) pictures show that granules are dominated by Methanosaeta-like microbes. Thus, the sludge characteristics at the start-up are of vital importance as they influence the sludge quality developed during the reactor operation and also the microbial communities retained.
Applied and environmental microbiology, 1992
The hydrophobicities and electrophoretic mobilities of isolates from methanogenic anaerobic granular sludge were measured and compared with those of strains from culture collections. All new isolates were highly hydrophobic, indicating that the upflow anaerobic sludge blanket reactor concept selects for hydrophobic bacteria. Methanothrix soehngenii, a methanogen often observed in methanogenic granular sludge, was highly hydrophobic and showed low electrophoretic mobility at pH 7. The role of this strain in the formation of methanogenic granular sludge is discussed.