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1.
2.
In this study, sludge was taken from a municipal wastewater treatment plant that contained a nearly equal number of archaeal
amoA genes (5.70 × 106 ± 3.30 × 105 copies mg sludge−1) to bacterial amoA genes (8.60 × 106 ± 7.64 × 105 copies mg sludge−1) and enriched in three continuous-flow reactors receiving an inorganic medium containing different ammonium concentrations:
2, 10, and 30 mM NH4+–N (28, 140, and 420 mg N l−1). The abundance and communities of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in enriched nitrifying
activated sludge (NAS) were monitored at days 60 and 360 of the operation. Early on, between day 0 and day 60 of reactor operation,
comparative abundance of AOA amoA genes to AOB amoA genes varied among the reactors depending on the ammonium levels found in the reactors. As compared to the seed sludge, the
number of AOA amoA genes was unchanged in the reactor with lower ammonium level (0.06 ± 0.04 mgN l−1), while in the reactors with higher ammonium levels (0.51 ± 0.33 and 0.25 ± 0.10 mgN l−1), the numbers of AOA amoA genes were deteriorated. By day 360, AOA disappeared from the ammonia-oxidizing consortiums in all reactors. The majority
of the AOA sequences from all NASs at each sampling period fell into a single AOA cluster, however, suggesting that the ammonium
did not affect the AOA communities under this operational condition. This result is contradictory to the case of AOB, where
the communities varied significantly among the NASs. AOB with a high affinity for ammonia were present in the reactors with
lower ammonium levels, whereas AOB with a low affinity to ammonia existed in the reactors with higher ammonium levels. 相似文献
3.
Pyrosequencing Reveals a Highly Diverse and Cultivar-Specific Bacterial Endophyte Community in Potato Roots 总被引:3,自引:0,他引:3
Daniel K. Manter Jorge A. Delgado David G. Holm Rachel A. Stong 《Microbial ecology》2010,60(1):157-166
In this study, we examined the bacterial endophyte community of potato (Solanum tuberosum) cultivar/clones using two different molecular-based techniques (bacterial automated ribosomal intergenic spacer analysis
(B-ARISA) and pyrosequencing). B-ARISA profiles revealed a significant difference in the endophytic community between cultivars
(perMANOVA, p < 0.001), and canonical correspondence analysis showed a significant correlation between the community structure and plant
biomass (p = 0.001). Pyrosequencing detected, on average, 477 ± 71 bacterial operational taxonomic units (OTUs, 97% genetic similarity)
residing within the roots of each cultivar, with a Chao estimated total OTU richness of 1,265 ± 313. Across all cultivars,
a total of 238 known genera from 15 phyla were identified. Interestingly, five of the ten most common genera (Rheinheimera, Dyadobacter, Devosia, Pedobacter, and Pseudoxanthomonas) have not, to our knowledge, been previously reported as endophytes of potato. Like the B-ARISA analysis, the endophytic
communities differed between cultivar/clones (∫-libshuff, p < 0.001) and exhibited low similarities on both a presence/absence (0.145 ± 0.019) and abundance (0.420 ± 0.081) basis. Seventeen
OTUs showed a strong positive (r > 0.600) or negative (r < −0.600) correlation with plant biomass, suggesting a possible link between plant production and endophyte abundance. This
study represents one of the most comprehensive assessments of the bacterial endophytic communities to date, and similar analyses
in other plant species, cultivars, or tissues could be utilized to further elucidate the potential contribution(s) of endophytic
communities to plant physiology and production. 相似文献
4.
Essential roles of eDNA and AI-2 in aerobic granulation in sequencing batch reactors operated at different settling times 总被引:1,自引:0,他引:1
Settling time has been considered as one of the most effective selection pressures for aerobic granulation in sequencing batch
reactors (SBRs), i.e., poorly settleable bioparticles would be washed out from SBRs, and the heavy and good settling ones
would be retained at a shorter setting time. However, its biological implication remains unclear. This study investigated
the microbiological mechanisms of aerobic granulation at different settling times. It provided experimental evidence for the
first time showing that a shorter settling time could enhance release of extracellular DNA through cell lysis, which in turn
initiated microbial aggregation leading to increased biomass size and density, while AI-2-mediated quorum sensing was found
not to be involved in initial aggregation. It was further shown that the AI-2-mediated quorum sensing system was activated
to regulate the growth and maturation of aerobic granules when the biomass density reached a threshold of 1.025 g ml−1. It appears from this study that a short settling time of SBR would induce microbiological and physiological responses of
bacteria which are required at different stages of aerobic granulation and provide new insights into biological mechanisms
of settling time-triggered aerobic granulation. 相似文献
5.
Nitrifying granules cultivation in a sequencing batch reactor at a low organics-to-total nitrogen ratio in wastewater 总被引:4,自引:0,他引:4
It is possible to cultivate aerobic granular sludge at a low organic loading rate and organics-to-total nitrogen (COD/N) ratio
in wastewater in the reactor with typical geometry (height/diameter = 2.1, superficial air velocity = 6 mm/s). The noted nitrification
efficiency was very high (99%). At the highest applied ammonia load (0.3 ± 0.002 mg NH4+–N g total suspended solids (TSS)−1 day−1, COD/N = 1), the dominating oxidized form of nitrogen was nitrite. Despite a constant aeration in the reactor, denitrification
occurred in the structure of granules. Applied molecular techniques allowed the changes in the ammonia-oxidizing bacteria
(AOB) community in granular sludge to be tracked. The major factor influencing AOB number and species composition was ammonia
load. At the ammonia load of 0.3 ± 0.002 mg NH4+–N g TSS−1 day−1, a highly diverse AOB community covering bacteria belonging to both the Nitrosospira and Nitrosomonas genera accounted for ca. 40% of the total bacteria in the biomass. 相似文献
6.
Phosphate Addition and Plant Species Alters Microbial Community Structure in Acidic Upland Grassland Soil 总被引:2,自引:0,他引:2
Agricultural improvement (addition of fertilizers, liming) of seminatural acidic grasslands across Ireland and the UK has
resulted in significant shifts in floristic composition, soil chemistry, and microbial community structure. Although several
factors have been proposed as responsible for driving shifts in microbial communities, the exact causes of such changes are
not well defined. Phosphate was added to grassland microcosms to investigate the effect on fungal and bacterial communities.
Plant species typical of unimproved grasslands (Agrostis capillaris, Festuca ovina) and agriculturally improved grasslands (Lolium perenne) were grown, and phosphate was added 25 days after seed germination, with harvesting after a further 50 days. Phosphate addition
significantly increased root biomass (p < 0.001) and shoot biomass (p < 0.05), soil pH (by 0.1 U), and microbial activity (by 5.33 mg triphenylformazan [TPF] g−1 soil; p < 0.001). A slight decrease (by 0.257 mg biomass-C g−1 soil; p < 0.05) in microbial biomass after phosphate addition was found. The presence of plant species significantly decreased soil
pH (p < 0.05; by up to 0.2 U) and increased microbial activity (by up to 6.02 mg TPF g−1 soil) but had no significant effect on microbial biomass. Microbial communities were profiled using automated ribosomal intergenic
spacer analysis. Multidimensional scaling plots and canonical correspondence analysis revealed that phosphate addition and
its interactions with upland grassland plant species resulted in considerable changes in the fungal and bacterial communities
of upland soil. The fungal community structure was significantly affected by both phosphate (R = 0.948) and plant species (R = 0.857), and the bacterial community structure was also significantly affected by phosphate (R = 0.758) and plant species (R = 0.753). Differences in microbial community structure following P addition were also revealed by similarity percentage analysis.
These data suggest that phosphate application may be an important contributor to microbial community structural change during
agricultural management of upland grasslands. 相似文献
7.
Anaerobic sequencing batch reactors for wastewater treatment: a developing technology 总被引:4,自引:0,他引:4
Zaiat M Rodrigues JA Ratusznei SM de Camargo EF Borzani W 《Applied microbiology and biotechnology》2001,55(1):29-35
This paper describes and discusses the main problems related to anaerobic batch and fed-batch processes for wastewater treatment.
A critical analysis of the literature evaluated the industrial application viability and proposed alternatives to improve
operation and control of this system. Two approaches were presented in order to make this anaerobic discontinuous process
feasible for industrial application: (1) optimization of the operating procedures in reactors containing self-immobilized
sludge as granules, and (2) design of bioreactors with inert support media for biomass immobilization.
Received: 22 May 2000 / Received revision: 20 July 2000 / Accepted: 21 July 2000 相似文献
8.
Berna Gerçe Thomas Schwartz Matthias Voigt Sebastian Rühle Silke Kirchen Annika Putz Peter Proksch Ursula Obst Christoph Syldatk Rudolf Hausmann 《Microbial ecology》2009,58(4):865-878
The aim of this study was to analyze successional changes in the bacterial community over a period of 6 months of cultivation
of Aplysina aerophoba sponges under different artificial cultivation conditions by use of denaturing gradient gel electrophoresis (DGGE). The cultivation
conditions varied concerning the water temperature (20 ± 2 °C and 25 ± 2 °C) of the aquaria, additional illumination of one
aquarium, and feeding of the sponges. Amplicons from DGGE separation of dominant colonizing or variably appearing bacteria
were sequenced and aligned for taxonomical identification. In addition, secondary metabolites typically found in A. aerophoba were analyzed to investigate changes in the natural product profile during cultivation. The cultivation of sponges under
any given condition did not lead to a depletion of their bacterial community in the course of the experiment. On the contrary,
the distinctive set of associated bacteria was maintained in spite of a dramatic loss of biomass and morphological degradation
during the cultivation period. Generally, all sequences obtained from the DGGE gels were related to bacteria of five phyla:
Actinobacteria, Cyanobacteria, α-Proteobacteria, γ-Proteobacteria, and Chloroflexi. Despite the overall stability of the bacterial community in A. aerophoba, an unambiguous variability was detected for the Cyanobacteria “A. aerophoba clone TK09”. This variability was ascribed to the predominant light conditions. The analysis of the metabolic pattern revealed
that the concentration of a class of characteristic-brominated compounds typically found in A. aerophoba, like aeroplysinin-1, aerophobin-1, aerophobin-2, and isofistularin-3, increased over the 6 months of cultivation. 相似文献
9.
Towards a reduction in excess sludge production in activated sludge processes: biomass physicochemical treatment and biodegradation 总被引:15,自引:0,他引:15
M. Rocher G. Goma A. Pilas Begue L. Louvel J. L. Rols 《Applied microbiology and biotechnology》1999,51(6):883-890
To decrease activated sludge production, microbial cell lysis can be amplified to enhance cryptic growth (biomass growth
on lysates). Cell breakage techniques (thermal, alkaline, acid) were studied to generate Alcaligenes eutrophus and sludge lysates and to evaluate their biodegradability. Gentle treatment conditions produced the best results. Complete
cell deactivation was obtained for temperatures higher than 55 °C. The release kinetics were similar for temperatures varying
from 60 °C to 100 °C. A 20-min incubation was suitable for reaching 80% of the maximum releasable carbon. In thermal-chemical
hydrolysis, NaOH was the most efficient for inducing cell lysis. Carbon release was a two-step process. First an immediate
release occurred, which was of the same order of magnitude for A. eutrophus and sludge [100–200 mg dissolved organic C (DOC) g total suspended solids (TSS)−1], followed by a post-treatment release. The second step was virtually equivalent to the first for sludge, and weaker for
A. eutrophus (<50 mg DOC g TSS−1). The biodegradability of the soluble fraction, both the immediate and the post-treatment carbon release, was investigated.
The optimal degradation yield, obtained with sludge cells, reached 55% after 48 h of incubation and 80% after 350 h. The most
consistent lysis and biodegradation results occurred at pH 10 and 60 °C after a 20-min incubation.
Received: 30 October 1998 / Received revision: 16 February 1999 / Accepted: 20 February 1999 相似文献
10.
We studied in batch reactors the kinetics and characterization of 70 °C, volatile fatty acids (VFAs)-grown, upflow anaerobic
sludge blanket granular sludge with 55 and 35 °C sludge as reference. The half-saturation constant (K
s), the inhibition constant (K
i), the maximum specific methane production rate (μCH4max), and the inhibition response coefficient (n) of the 70 °C sludge were 6.15 mM, 48.2 mM, 0.132 h−1, and 2.48, respectively, while no inhibition occurred at 55 and 35 °C, where the K
s was 3.67 and 3.82 mM, respectively. At 70 °C, the highest initial specific methanogenic activity (ISMA, 0.311 gCH4-COD per gram volatile solids per day) on VFAs was about 12–15% lower than that on acetate and three to four times less than
the ISMA for the 55 and 35 °C sludge. In the acetate conversion study, residual acetate (79 mg l−1) at 70 °C was three to five times higher than that at 55 and 35 °C. Further, the methane produced as percentage of the acetate
consumed at 70 °C (89%) was lower than that at 55 (95%) and 35 °C (97%). At 70 °C, 10% of the ISMA remained after 15 days
of starvation as compared to 26% (55 °C) and 92% (35 °C) after 30 days of starvation. Thus, the kinetics of the 70 °C granular
sludge seem to differ from those at 55 and 35 °C.
Received: 1 February 1999 / Accepted: 20 March 1999 相似文献
11.
Auguet JC Montanié H Hartmann HJ Lebaron P Casamayor EO Catala P Delmas D 《Microbial ecology》2009,57(2):295-306
Batch culture experiments using viral enrichment were conducted to test the response of a coastal bacterial community to autochthonous
(i.e., co-existing) or allochthonous riverine viruses. The effects of viral infections on bacterial dynamics and activity
were assessed by epifluorescence microscopy and thymidine incorporation, respectively, whereas the effect of viral infection
on bacterial community composition was examined by polymerase chain reaction-single strand conformation polymorphism 16S ribosomal
RNA fingerprinting. The percentages of high nucleic acid-containing cells, evaluated by flow cytometry, were significantly
correlated (r
2 = 0.91, n = 12, p < 0.0001) to bacterial production, making this value a good predictor of active cell dynamics along the study. While confinement
and temperature were the two principal experimental factors affecting bacterial community composition and dynamics, respectively,
additions of freshwater viruses had significant effects on coastal bacterial communities. Thus, foreign viruses significantly
reduced net bacterial population increase as compared to the enrichment treated with inactivated virus. Moreover, freshwater
viruses recurrently and specifically affected bacterial community composition, as compared to addition of autochthonous viruses.
In most cases, the combined treatment viruses and freshwater dissolved organic matter helped to maintain or even enhance species
richness in coastal bacterial communities in agreement to the ‘killing the winner’ hypothesis. Thus, riverine virus input
could potentially influence bacterial community composition of the coastal bay albeit with modest modification of bulk bacterial
growth.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
12.
Bisson Isabelle-A. Marra Peter P. Burtt Jr Edward H. Sikaroodi Masoumeh Gillevet Patrick M. 《Microbial ecology》2009,58(1):212-220
Migratory birds can be efficient dispersers of pathogens, yet we know little about the effect of migration and season on the
microbial community in avian plumage. This is the first study to describe and compare the microbial plumage community of adult
and juvenile migratory birds during the annual cycle and compare the plumage community of migrants to that of resident birds
at both neotropical and nearctic locations. We used length heterogeneity PCR (16S rRNA) to describe the microbial assemblage
sampled from the plumage of 66 birds in two age classes and from 16 soil samples. Resident birds differed significantly in
plumage microbial community composition from migrants (R ≥ 0.238, P < 0.01). Nearctic resident birds had higher plumage microbial diversity than nearctic migrants (R = 0.402, P < 0.01). Plumage microbial composition differed significantly between fall premigratory and either breeding (R ≥ 0.161, P < 0.05) or nonbreeding stages (R = 0.267, P < 0.01). Six bacterial operational taxonomic units contributed most to the dissimilarities found in this assay. Soil microbial
community composition was significantly different from all samples of plumage microbial communities (R ≥ 0.700, P < 0.01). The plumage microbial community varies in relation to migration strategy and stage of the annual cycle. We suggest
that plumage microbial acquisition begins in the first year at natal breeding locations and reaches equilibrium at the neotropical
wintering sites. These data lead us to conclude that migration and season play an important role in the dynamics of the microbial
community in avian plumage and may reflect patterns of pathogen dispersal by birds. 相似文献
13.
Active biomass retention is a technical challenge in anaerobic digester treating dilute animal manure that contains solids particles. A strategy was tested using fibers in the dairy manure as biomass carriers by controlling settling time. Settling time ranging from 0.5 to 60 min were applied to eight anaerobic sequencing batch reactors to investigate their effects on active biomass retention in anaerobic digestion of flushed dairy manure. Results revealed that there existed a critical settling time at 2 min at which only minimum amount of active biomass was retained, and as settling time increased or decreased from this threshold, more active biomass could be retained. Gravity settling and selection pressure theories were suggested to account for the results. A model integrating these two effects was developed and verified with the experimental data. Knowledge derived from this study may lead to innovative bacterial retention technology for cost-effective anaerobic digestion of dairy wastes. 相似文献
14.
Changes in freshwater bacterial community composition during measurements of microbial and community respiration 总被引:2,自引:0,他引:2
Gattuso Jean-Pierre; Peduzzi Sandro; Pizay Marie-Dominique; Tonolla Mauro 《Journal of plankton research》2002,24(11):1197-1206
The respiration rates of a pelagic community and of its microbialfraction (< 1.2 µm) were measured at two depths inthe oxic layer of a meromictic alpine lake (Cadagno, Switzerland)using the oxygen technique. The duration of the incubationswere 12, 24 and 55 h. Bacterioplankton abundance (DAPI counts)and composition (whole cell hybridization using 11 group-specificrRNA-targeted oligonucleotide probes) were measured during theincubations. Respiration generally increased with time, especiallyin the microbial fraction, or remained similar. This resultwas not always consistent with changes in bacterial abundanceand cell volume. The composition of the community also changedduring the incubations. The abundance of ß-Proteobacteriaincreased during the course of all the experiments. These resultsextend the previous conclusions drawn in marine environmentsto fresh waters and demonstrate that, in addition to changesin bacterial abundance, cell volume and biomass, changes inthe taxonomic composition of the bacterial community can occurduring discrete incubations of freshwater planktonic communities. 相似文献
15.
Species and material considerations in the formation and development of microalgal biofilms 总被引:2,自引:0,他引:2
The development of microalgal biofilms has received very limited study despite its relevance in the design of photobioreactors
where film growth may be advantageous for biomass separation or disadvantageous in fouling surfaces. Here, the effects of
species selection, species control, and substrate properties on biofilms of Scenedesmus obliquus and Chlorella vulgaris were investigated. Experiments were conducted in batch culture and in continuous culture modes in a flow cell. Cell growth
was monitored using confocal laser scanning microscopy and gravimetrically. Species selection and species control had significant
effects on biofilm development. On non-sterile wastewater, C. vulgaris shifted from primarily planktonic (23.7% attachment) to primarily sessile (79.8% attachment) growth. The biofilms that developed
in non-sterile conditions were thicker (52 ± 19 μm) than those grown in sterile conditions (7 ± 6 μm). By contrast, S. obliquus attained similar thicknesses (54 ± 31 and 53 ± 38 μm) in both sterile and non-sterile conditions. Neither species was able
to dominate a non-sterile biofilm. The effect of substrate surface properties was minimal. Both species grew films of similar
thickness (∼30 μm for S. obliquus, <10 μm for C. vulgaris) on materials ranging from hydrophilic (glass) to hydrophobic (polytetrafluoroethylene). Surface roughness created by micropatterning
the surface with 10 μm grooves did not translate into long-term increases in biofilm thickness. The results indicate that
species selection and control are more important than surface properties in the development of microalgal biofilms. 相似文献
16.
Microbial community structure in the subtropical north-east Atlantic Ocean was compared between 2 years and variation attributed
to environmental variables. Surface seawater communities were analysed by flow cytometry and fluorescence in situ hybridisation.
Probes specific to Alphaproteobacteria, Cyanobacteria, Gammaproteobacteria and Bacteroidetes identified 67–100% of cells. Due to natural variation in the study region due to the occurrence of major currents and islands,
data could not be pooled but were instead divided between distinct water masses. Community structure did not differ greatly
around the Cape Verde Islands between sampling periods but varied substantially in the open ocean, suggesting different environmental
perturbations favour specific bacterial groups. Wind speed varied significantly between years, with moderate to strong breeze
in winter 2008 and gales in winter 2006 (8.9 ± 0.2 ms−1 and 16.0 ± 0.4 ms−1, respectively). Enhanced wind-driven turbulence was associated with domination by the SAR11 clade of Alphaproteobacteria, which were present at 2.4-fold in the abundance of Prochlorococcus (41.8 ± 1.6% cells, compared to 17.7 ± 7.1%). Conversely, the calmer conditions of 2008 seemed to favour Prochlorococcus (40.0 ± 1.2% cells). Prochlorococcus high-light adapted clade HLI were only numerous during wind-driven turbulence, whereas oligotrophic-adapted clade HLII dominated
under calm conditions. Bacteroidetes were most prominent in turbulent conditions (9.5 ± 1.3% cells as opposed to 4.7 ± 0.3%), as were Synechococcus. In 2008, a considerable dust deposition event occurred in the region, which may have led to the substantial Gammaproteobacteria population (22.5 ± 4.0% cells compared to 4.6 ± 0.6% in 2006). Wind-driven turbulence may have a significant impact on microbial
community structure in the surface ocean. Therefore, community change following dust storm events may be linked to associated
wind in addition to dust-derived nutrients. 相似文献
17.
The influence of low temperature (5–29 °C) on the methanogenic activity of non-adapted digested sewage sludge and on temperature/leachate-adapted
biomass was assayed by using municipal landfill leachate, intermediates of anaerobic degradation (propionate) and methane
precursors (acetate, H2/CO2) as substrates. The temperature dependence of methanogenic activity could be described by Arrhenius-derived models. However,
both substrate and adaptation affected the temperature dependence. The adaptation of biomass in a leachate-fed upflow anaerobic
sludge-blanket reactor at approximately 20 °C for 4 months resulted in a sevenfold and fivefold increase of methanogenic activity
at 11 °C and 22 °C respectively. Both acetate and H2/CO2 were methanized even at 5 °C. At 22 °C, methanogenic activities (acetate 4.8–84 mM) were 1.6–5.2 times higher than those
at 11 °C. The half-velocity constant (K
s) of acetate utilization at 11 °C was one-third of that at 22 °C while a similar K
i was obtained at both temperatures. With propionate (1.1–5.5 mM) as substrate, meth‐anogenic activities at 11 °C were half
those at 22 °C. Furthermore, the residual concentration of the substrates was not dependent on temperature. The results suggest
that the adaptation of biomass enables the achievement of a high treatment capacity in the anaerobic process even under psychrophilic
conditions.
Received: 23 December 1996 / Received last revision: 18 June 1997 / Accepted: 23 June 1997 相似文献
18.
Diatom composition and biomass were investigated in the nearshore water (<30 m in depth) of Maxwell Bay, Antarctica during
the 1992/1993 austral summer. Epiphytic or epilithic diatoms such as Fragilaria striatula, Achnanthes brevipes var. angustata and Licmophora spp. dominated the water column microalgal populations. Within the bay, diatom biomass in surface water was several times
higher at the nearshore (2.4–14 μg C l-1) than at the offshore stations (>100 m) (1.2–3.2 μg C l-1) with a dramatic decrease towards the bay mouth. Benthic forms accounted for >90% of diatom carbon in all nearshore stations,
while in the offshore stations planktonic forms such as Thalassiosira antarctica predominated (50–>90%). Microscopic examination revealed that many of these diatoms have become detached from a variety of
macroalgae growing in the intertidal and shallow subtidal bottoms. Epiphytic diatoms persistently dominated during a 19-day
period in the water column at a fixed nearshore station, and the biomass of these diatoms fluctuated from 0.86 to 53 μg C l-1. A positive correlation between diatom biomass and wind speed strongly suggests that wind-driven resuspension of benthic
forms is the major mechanism increasing diatom biomass in the water column.
Received: 28 April 1995/Accepted: 1 April 1996 相似文献
19.
A Konopka T Zakharova L Oliver R F Turco 《Journal of industrial microbiology & biotechnology》1997,18(4):235-240
In a continuous flow bioreactor seeded with microbes from municipal activated sludge, complete organic carbon oxidation of
simulated graywater (wastewater produced in human residences, excluding toilet wastes) was achieved at dilution rates up
to 0.36 h−1 in the presence of 64.1 μ M linear alkylbenzenesulfonate (LAS) L−1. At LAS concentrations of 187 μ M, the system functioned only at dilution rates up to 0.23 h−1, and the biomass yield was two-fold lower. There were physiological changes in the microbial communities under different
operating conditions, as measured by specific contents of ATP and extracellular hydrolases as well as the respiratory potential
of the biomass. LAS inhibited the activity of LAS-degrading microbes at >150 μ M LAS, and the activity of other microbes at >75 μ M LAS. Chemical analysis of graywater indicated that samples consisted primarily of biological polymers (proteins and polysaccharides)
and lower concentrations of surfactants. Biological remediation of graywater is possible, although treatment efficiency is
influenced by the operating conditions and wastestream composition.
Received 08 July 1996/ Accepted in revised form 14 November 1996 相似文献
20.
Mean settling velocity of granular sludge in full-scale UASB (upflow anaerobic sludge blanket) and EGSB (expanded granular sludge bed) reactors was evaluated by settling column tests, and a settling velocity model based on the experimental results and available literature data was developed. It is concluded that the settling velocity should be calculated by the Allen formula, because the settling process of the granules is in the category of intermediate flow regime rather than in the laminar flow one. The comparison between calculated and measured values of the settling velocity shows an excellent agreement, with an average relative error of 4.04%. A simple but reliable mathematical method to determine the settling velocity is therefore proposed. 相似文献