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1.
In continuous aerobic treatment of artificial sewage by activated sludge, the rate of removal of chemical oxygen demand (COD) was markedly enhanced by the presence of cross-linked poly-4-vinylpyridine (PVP). The concentration of dissolved oxygen (DO) was also low in the presence of PVP. The extent of improvement in COD removal increased with increases in substrate load and the surface area of the PVP in the working space of the test apparatus. These results suggest an increase of the bacterial population resulting from the presence of the PVP. However, formation of measurable biofilm was not detected on the surface of the PVP during continuous aerobic treatment.  相似文献   

2.
Chlorophenol degradation was studied by combined anaerobic–aerobic treatments as a single or multi-substrate system. 2,4-Dichlorophenol (2,4-DCP) was degraded to the extent of 52 and 78% in up-flow anaerobic sludge blanket (UASB) and aerobic suspended growth (ASG) reactors respectively, at organic loading rates of 0.18kg/m3/day and hydraulic retention time of 26.4h in the presence of glucose. The UASB represents the dominating facultative anaerobic microbial population. When the effluent from the anaerobic reactor (UASB) was subjected to aerobic treatment on the ASG reactor, 2,4-DCP and COD removals of 86 and 95% respectively were achieved. Aerobic degradation of chlorophenol by acclimated mixed bacterial isolates was found to be sequential: 2-Chlorophenol (2-CP) and 4-CP were degraded first, followed by 2,4-DCP and 2,4,6-Trichlorophenol (2,4,6-TCP) while the contrary was obtained in anaerobic degradation. In anaerobic degradation by acclimated mixed bacterial cells, 2,4-DCP and 2,4,6-TCP were degraded first followed by mono-chlorophenols. The anaerobic/aerobic bioreactors were most efficient when operated in sequence (series) rather than in parallel.  相似文献   

3.
The objective of this study was to model a typical dairy waste stream, monitor the chemical and bacterial population dynamics that occur during aerobic or anaerobic treatment and subsequent storage in a simulated lagoon, and compare them to those of waste held without treatment in a simulated lagoon. Both aerobic and anaerobic treatment methods followed by storage effectively reduced the levels of total solids (59 to 68%), biological oxygen demand (85 to 90%), and sulfate (56 to 65%), as well as aerobic (83 to 95%), anaerobic (80 to 90%), and coliform (>99%) bacteria. However, only aerobic treatment reduced the levels of ammonia, and anaerobic treatment was more effective at reducing total sulfur and sulfate. The bacterial population structure of waste before and after treatment was monitored using 16S rRNA gene sequence libraries. Both treatments had unique effects on the bacterial population structure of waste. Aerobic treatment resulted in the greatest change in the type of bacteria present, with the levels of eight out of nine phyla being significantly altered. The most notable differences were the >16-fold increase in the phylum Proteobacteria and the approximately 8-fold decrease in the phylum Firmicutes. Anaerobic treatment resulted in fewer alterations, but significant decreases in the phyla Actinobacteria and Bacteroidetes, and increases in the phyla Planctomycetes, Spirochetes, and TM7 were observed.  相似文献   

4.
The objective of this study was to model a typical dairy waste stream, monitor the chemical and bacterial population dynamics that occur during aerobic or anaerobic treatment and subsequent storage in a simulated lagoon, and compare them to those of waste held without treatment in a simulated lagoon. Both aerobic and anaerobic treatment methods followed by storage effectively reduced the levels of total solids (59 to 68%), biological oxygen demand (85 to 90%), and sulfate (56 to 65%), as well as aerobic (83 to 95%), anaerobic (80 to 90%), and coliform (>99%) bacteria. However, only aerobic treatment reduced the levels of ammonia, and anaerobic treatment was more effective at reducing total sulfur and sulfate. The bacterial population structure of waste before and after treatment was monitored using 16S rRNA gene sequence libraries. Both treatments had unique effects on the bacterial population structure of waste. Aerobic treatment resulted in the greatest change in the type of bacteria present, with the levels of eight out of nine phyla being significantly altered. The most notable differences were the >16-fold increase in the phylum Proteobacteria and the approximately 8-fold decrease in the phylum Firmicutes. Anaerobic treatment resulted in fewer alterations, but significant decreases in the phyla Actinobacteria and Bacteroidetes, and increases in the phyla Planctomycetes, Spirochetes, and TM7 were observed.  相似文献   

5.
The differential rates of formation of total extracellular protein and alpha-toxin by Staphylococcus aureus (Wood 46) were determined during aerobic growth, at 37 degrees C, in a complex medium containing 0.0, 0.25 or 1.0% (wt/vol) glucose. Different inocula were employed from 1% (vol/vol) of an overnight culture to 100% where bacterial cells were washed and resuspended in fresh medium without change in density. It was shown that under all conditions examined the differential rates of total extracellular protein formation exhibited a biphasic pattern characteristic of regulation based on 'competition'. This biphasic pattern was maintained even in the presence of a large inoculum and a high glucose concentration, conditions considered to favour the onset of catabolite repression. However, a lowering of the initial rate was observed with increasing glucose suggesting the superimposition of catabolite repression as a modulating effect under extreme conditions. In the case of the specific extracellular protein component, alpha-toxin, its differential rate of formation paralleled total exoprotein in all except the condition most favourable for catabolite accumulation when a deviation consistent with a pronounced catabolite repression of this component was demonstrated which was not pH-dependent.  相似文献   

6.
Aerobic granules were cultivated under temporal alternating aerobic and anoxic conditions without the presence of a carrier material in a sequencing batch reactor (SBR) with a high column height/column diameter ratio. The reactor was operated for 6h per cycle (aerobic: 4.75 h, anoxic: 1.25 h). To determine a new parameter for the definition of aerobic granules, a protocol of 4,6-diamidino-2-phenylindole hydrochloride staining and fluorescence image processing was developed. The d(tm) analysis showed that the increase in the chemical oxygen demand (COD) loading rate promoted no more growth of the aerobic granules. It was inconsistent with the results of the analysis of the sludge volume index (SVI) value but matched well with the results of the COD and nitrogen removal of the SBR and the particle size distribution by LS-PSA. The optimum COD loading rate for aerobic granulation in the SBR was 2.52 kg/m(3)d. When d(tm) was correlated with the biomass concentration and the SVI value during the period of granule formation, d(tm) could be used as a more sensitive and accurate parameter for classifying aerobic granules and optimizing the operational conditions for aerobic granulation processes.  相似文献   

7.
Aerobic nitrification-denitrification by heterotrophic Bacillus strains   总被引:19,自引:0,他引:19  
Twenty-four Bacillus strains predominantly outgrown in a night soil treatment system were isolated and characterized. Under various culture conditions, cell interactions took place among them and cell population changed. Maximum removal of NH4+-N and cell production by the isolates occurred under the conditions of 30% DO and C/N ratio of 8. Five dominant isolates were identified to be species of Bacillus cereus, Bacillus subtilis and Bacillus licheniformis with similarities of 78-94%. Additions of 0.8% peptone and 0.3% yeast extract to a basal medium influenced the growth of isolates and the removal of NH4+-N in flask culture. Metal ions such as Ca2+, Fe2+ and Mg2+ had a similar effect. The specific growth rates of the five isolates were found to be in a range of 0.43-0.55 h(-1). During the flask experiment of nitrogen removal under aerobic growth conditions, active nitrification by the isolates occurred largely in 1h with a decrease of COD and alkalinity reduced to only 74.6% of theoretical value. From the nitrogen balance, the percentage of nitrogen lost in the flask culture was estimated to be 33.0%, which was presumed to convert to N2 gas. This conversion of ammonia to N2 without formation of nitrous oxide under aerobic growth conditions was confirmed by GC analysis. From all the results, it has been found that the Bacillus strains were able to occur simultaneously aerobic nitrification/denitrification and the B3 process using the Bacillus strains seemed to possess some economic advantages.  相似文献   

8.
The low bioavailability of polychlorinated biphenyls (PCBs) in soils often results in their slow and partial aerobic biodegradation. The process can be enhanced by supplementing soils with cyclodextrins. However, pure cyclodextrins are expensive and we have therefore explored the use of a less costly technical grade mixture of randomly methylated-beta-cyclodextrins (RAMEB). RAMEB was tested at 0, 1, 3 and 5% (w/w) in the aerobic bioremediation and detoxification of a loamy-, a humic- and a sandy-soil, each artificially contaminated with a PCB-containing transformer oil (added PCBs: about 450 or 700 mg/kg), inoculated with an exogenous aerobic PCB-biodegrading bacterial co-culture and treated in slurry- and solid-phase laboratory conditions. Significant depletions of the spiked PCBs were observed in all microcosms of the three soils after 90 days of treatment; however, interesting yields of PCB dechlorination and detectable decreases of the original soil ecotoxicity were observed in the slurry-phase microcosms. RAMEB generally enhanced PCB-metabolism with effects which were dependent on the concentration at which it was applied, the physical-chemical nature of the amended soil, and the soil treatment conditions employed. RAMEB, which was slowly metabolized by soil microorganisms, enhanced the presence of PCBs and PCB-cometabolizing bacteria in the soil-water phase, suggesting that RAMEB enhances aerobic biodegradation of PCBs by increasing pollutant bioavailability in soil microcosms.  相似文献   

9.
Pseudomonas putida ATCC 17514 was used as a model strain to investigate the characteristics of bacterial growth in the presence of solid fluorene and phenanthrene. Despite the lower water-solubility of phenanthrene, P. putida degraded this polycyclic aromatic hydrocarbon (PAH) at a maximum observed rate of 1.4 +/- 0.1 mg L(-1) h(-1), higher than the apparent degradation rate of fluorene, 0.8 +/- 0.07 mg L(-1) h(-1). The role of physiological processes on the biodegradation of these PAHs was analyzed and two different uptake strategies were identified. Zeta potential measurements revealed that phenanthrene-grown cells were slightly more negatively charged (-57.5 +/- 4.7 mV) than fluorene-grown cells (-51.6 +/- 4.9 mV), but much more negatively charged than glucose-grown cells (-26.8 +/- 3.3 mV), suggesting that the PAH substrate induced modifications on the physical properties of bacterial surfaces. Furthermore, protein-to-exopolysaccharide ratios detected during bacterial growth on phenanthrene were typical of biofilms developed under physicochemical stress conditions, caused by the presence of sparingly water-soluble chemicals as the sole carbon and energy source for growth, the maximum value for TP/EPS during growth on phenanthrene (1.9) being lower than the one obtained with fluorene (5.5). Finally, confocal laser microscopy observations using a gfp-labeled derivative strain revealed that, in the presence of phenanthrene, P. putida::gfp cells formed a biofilm on accessible crystal surfaces, whereas in the presence of fluorene the strain grew randomly between the crystal clusters. The results showed that P. putida was able to overcome the lower aqueous solubility of phenanthrene by adhering to the solid PAH throughout the production of extracellular polymeric substances, thus promoting the availability and uptake of such a hydrophobic compound.  相似文献   

10.
Succession of bacterial communities during the first 36 h of biofilm formation in coastal water was investigated at 3 approximately 15 h intervals. Three kinds of surfaces (i.e., acryl, glass, and steel substratum) were submerged in situ at Sacheon harbor, Korea. Biofilms were harvested by scraping the surfaces, and the compositions of bacterial communities were analyzed by terminal restriction fragment length polymorphism (T-RFLP), and cloning and sequencing of 16S rRNA genes. While community structure based on T-RFLP analysis showed slight differences by substratum, dramatic changes were commonly observed for all substrata between 9 and 24 h. Identification of major populations by 16S rRNA gene sequences indicated that gamma-Proteobacteria (Pseudomonas, Acinetobacter, Alteromonas, and uncultured gamma-Proteobacteria) were predominant in the community during 0 approximately 9 h, while the ratio of alpha-Proteobacteria (Loktanella, Methylobacterium, Pelagibacter, and uncultured alpha-Proteobacteria) increased 2.6 approximately 4.8 folds during 24 approximately 36 h of the biofilm formation, emerging as the most predominant group. Previously, alpha-Proteobacteria were recognized as the pioneering organisms in marine biofilm formation. However, results of this study, which revealed the bacterial succession with finer temporal resolution, indicated some species of gamma-Proteobacteria were more important as the pioneering population. Measures to control pioneering activities of these species can be useful in prevention of marine biofilm formation.  相似文献   

11.
Combination of anaerobic–aerobic sequencing processes result in both anaerobic color removal and aerobic aromatic amine removal during the treatment of dye-containing wastewaters. The aim of the present study was to gain more insight into the competitive biochemical reactions between sulfate and azo dye in the presence of glucose as electron donor source. For this aim, anaerobic–aerobic sequencing batch reactor fed with a simulated textile effluent including Remazol Brilliant Violet 5R (RBV 5R) azo dye was operated with a total cycle time of 12 h including anaerobic (6 h) and aerobic cycles (6 h). Microorganism grown under anaerobic phase of the reactor was exposed to different amounts of competitive electron acceptor (sulfate). Performance of the anaerobic phase was determined by monitoring color removal efficiency, oxidation reduction potential, color removal rate, chemical oxygen demand (COD), color, specific anaerobic enzyme (azo reductase) and aerobic enzyme (catechol 1,2-dioxygenase), and formation of aromatic amines. The presence of sulfate was not found to significantly affect dye decolorization. Sulfate and azo dye reductions took place simultaneously in all operational conditions and increase in the sulfate concentration generally stimulated the reduction of RBV 5R. However, sulfate accumulation under anaerobic conditions was observed proportional to increasing sulfate concentration.  相似文献   

12.
The response of a mixed microbial culture to different feed compositions, that is, containing benzoate and pyruvate as sole carbon sources at different levels, was studied in a chemostat with a 48-h hydraulic residence time under cyclic aerobic and anoxic (denitrifying) conditions. The cyclic bacterial culture was well adapted to different feed compositions as evidenced by the lack of accumulation of benzoate or pyruvate in the chemostat. Both the benzoate-degrading capabilities and the in vitro catechol 2,3-dioxygenase (C23DO) activities of the cyclic bacterial cultures were in direct proportion to the flux through the chemostat of the substrate degraded by the pathway containing C23DO, with some exceptions. The quantity of C23DO showed a transient decrease during the initial portion of the aerobic period before returning to the level present during the anoxic period. That decrease was most likely caused by the production of H(2)O(2) by the cells upon being returned to aerobic conditions.  相似文献   

13.
AIMS: To identify the dominant culturable and nonculturable microbiota of rainbow trout intestine. METHODS AND RESULTS: Microbial density of rainbow trout intestine was estimated by direct microscopic counts (4',6-diamidino-2-phenylindole, DAPI) and by culturing on tryptone soya agar (TSA). Differential gradient gel electrophoresis analysis of bacterial DNA from intestinal samples, re-amplification of bands and sequence analysis was used to identify the bacteria that dominated samples where aerobic counts were < or =2% of the DAPI counts. 16S rDNA gene sequences of 146 bacterial isolates and three sequences of uncultured bacteria were identified. A set of oligonucleotide probes was constructed and used to detect and enumerate the bacterial community structure of the gastrointestinal tract of rainbow trout by fluorescence in situ hybridization (FISH). Members of the gamma subclass of Proteobacteria (mainly Aeromonas and Enterobacteriaceae) dominated the bacterial population structure. Acinetobacter, Pseudomonas, Shewanella, Plesiomonas and Proteus were also identified together with isolates belonging to the beta subclass of Proteobacteria and Gram-positive bacteria with high and low DNA G + C content. In most samples, the aerobic count (on TSA) was 50-90% of the direct (DAPI) count. A bacterium representing a previously unknown phylogenetic lineage with only 89% 16S rRNA gene sequence similarity to Anaerofilum pentosovorans was detected in intestinal samples where aerobic counts were < or =2% of direct (DAPI) counts. Ten to 75% of the microbial population in samples with low aerobic counts hybridized (FISH) with a probe constructed against this not-yet cultured bacterium. CONCLUSIONS: Proteobacteria belonging to the gamma subclass dominated the intestinal microbiota of rainbow trout. However, in some samples the microflora was dominated by uncultivated, presumed anaerobic, micro-organisms. The bacterial population structure of rainbow trout intestine, as well as total bacterial counts, varied from fish to fish. SIGNIFICANCE AND IMPACT OF THE STUDY: Good correlation was seen between cultivation results and in situ analysis, however, a molecular approach was crucial for the identification of organisms uncultivated on TSA.  相似文献   

14.
Recently, some research in the field of enhanced biological phosphorus removal (EBPR) has been focused on studying systems where the electron donor (substrate) and the electron acceptor (nitrate or oxygen) are present simultaneously. This can occur, for example, in a full scale wastewater treatment plant during heavy rainfall periods when the anaerobic hydraulic retention time is temporarily shortened. To study this situation that could induce EBPR failure, the operation of a sequencing batch reactor (SBR) working under alternating anaerobic-aerobic conditions with an enriched EBPR population (50% Candidatus Accumulibacter phosphatis and less than 1% Candidatus Competibacter phosphatis) was shifted to strict aerobic operation. Seven cycle studies were performed during the 11 days of aerobic operation. Net P-removal was observed in this aerobic SBR during the first 4 days of operation but the system could not achieve net-P removal after this period, although the microbial composition, in terms of percentage of Accumulibacter and Competibacter, did not change significantly. The observed changes in the different compounds analysed (phosphorus, acetate, glycogen and PHB) as well as in the OUR profile indicate that metabolic changes are produced for the adaptation of PAO to aerobic conditions.  相似文献   

15.
The clinical efficacy and safety of intravenously administered imipenem/cilastatin in the treatment of 45 patients with severe bacterial septicemia due to intra-abdominal abscesses, respiratory and urinary tract as well as skin, soft tissue and bone infections was studied in the prospective and open trial. The in vitro antimicrobial activity of imipenem has been assessed on the basis of 909 bacterial strains isolated from patients treated and non-treated with imipenem/cilastatin. Among them were 526 Gram-negative, 370 Gram-positive aerobic bacteria and 13 Gram-negative anaerobic bacteria (Bacteroides sp.). Pathogen susceptibility to imipenem was determined with a disc-diffusion technique using Merck, Sharp Dohme sensitive discs containing 10 mcg of imipenem. Highly sensitive to imipenem were 96.8% of Gram-negative 82.7% of Gram-positive aerobic bacteria and 100% of Bacteroides sp. All patients, in whom evident foci of infection e.g. intra-abdominal abscesses were discovered, were operated on. The dosage of imipenem/cilastatin ranged from 1.5 to 2.0 g/24 h. Clinical cure and bacteriological elimination was achieved in 39 (86.7%) of patients while 6 (13.3%) showed marked clinical improvement. Before and during therapy, aerobic and anaerobic cultures were taken from accessible sites. All specimens were worked up using conventional bacteriological techniques. Before during and after therapy, samples for hematology, biochemistry and urinanalysis were obtained. Adverse clinical effects were noted in 2 (4.4%) patients. One had nausea and vomiting which were probably related to rapid infusion and disappeared after increasing the administration time, and one had transient diarrhea. In conclusion, imipenem/cilastatin was a well tolerated and effective drug in the treatment of life-threatening surgical infections.  相似文献   

16.
Seven aerobic bacterial strains were isolated from pulp paper mill waste and screened for pentachlorophenol (PCP) tolerance on PCP containing mineral salt agar medium (MSM). The organism was characterized by 16S rDNA sequencing which showed 99.7% sequence similarity with Serratia marcescens. PCP degradation was routinely monitored with spectrophotometric analysis and further confirmed by HPLC analysis. Among seven strains, ITRC S7 was found to degrade up to 90.33% of 1.127 mM (300 mg/l) of PCP and simultaneous release of chloride ion (2.435 mM) emphasized the bacterial dechlorination in the medium in presence of glucose as an additional carbon and energy source under optimized condition within 168 h incubation. In absence of glucose bacterium was unable to utilize PCP indicating the phenomenon of co-metabolism. Bacterium was identified as S. marcescens (AY927692), was a novel and potential aerobic bacterial strain capable of degrading PCP in axenic condition. Further, this strain may be used for bioremediation of PCP containing pulp paper mill waste in the environment.  相似文献   

17.
When S. mansoni adults were cultured in vitro for 12 days in a diphasic medium, their gross morphology, motor activity, frequency of sexual pairings, rates of glucose utilization and of lactic acid production were the same in the presence (90% N2/5% O2/5% CO2) or absence (95% N2/5% CO2) of oxygen. Therefore, no Pasteur effect, nor any reduction in lactic acid formation, was demonstrable under aerobic conditions. While aerobic conditions did not affect the rate of glycolysis, they had a marked effect on egg production. In the presence of oxygen, the rate of egg-laying reached a maximum between days 4 and 6. The average number of viable eggs produced per worm pair during this period was 118 (Sx equals 2.2), which is within the overall range (68 to 248) recorded by others for this same strain in vivo. Conversely, under anaerobic conditions in vitro, virtually no eggs were laid. It remains to be determined whether oxidative metabolism actually is required for energy to produce eggs, or whether some reaction yielding no ATP is essential for completion of their developmental process, such as tanning of the eggshall brought about by the oxidation of some phenolic compounds.  相似文献   

18.
The aim of this study was to evaluate anthracene removal using activated soil reactors, previously inoculated, under both aerobic and anaerobic conditions. In the reactors, the soil was maintained at 60% moisture (weight basis), room temperature, in the dark, and under constant agitation at 100 rpm. Two experiments were run during and after acclimatization to evaluate anthracene removal under both aerobic and anaerobic conditions. The first one took place during inoculum acclimatization using three different concentrations of anthracene (50, 100, and 500 mg anthracene/L per day) during 90 days. The second experiment took place after acclimatization (during 132 days). The results of anthracene removal were compared with controls in which no additional inoculum was added. During the two experiments, the behavior of pH, chemical oxygen demand (COD), and biogas production was evaluated. Results indicate that the bacterial community adapted for removal of anthracene became enriched through the acclimatization process. Anthracene biodegradation occurred in the soil model with both types of reactors (aerobic and anaerobic), but the rates and extent of biodegradation in the aerobic reactor were higher (95%) than those in anaerobic conditions (74%). Microbial activity also contributed to enhancing bioremediation in the soil by reducing anthracene sorption.  相似文献   

19.
Seminal fluid was collected by manual ejaculation from 95 dogs. Quantitative aerobic bacterial, qualitative anaerobic bacterial and mycoplasma cultures were performed on the seminal fluid, and their association with presence of inflammatory cells present in the pellet formed after centrifugation of the fluid was investigated. There was a clinically meaningful aerobic bacterial growth in 28.4%, anaerobic bacterial growth in 13.7%, and mycoplasma growth in 57.9% of the seminal fluid samples. Presence of inflammatory cytology was statistically associated with clinically meaningful aerobic bacterial growth. However, of the 78 dogs (82.1%) with clinically meaningful growth of at least one aerobic, anaerobic or mycoplasma organism, 43 (55.1%) had non-inflammatory seminal fluid cytology.  相似文献   

20.
In the present study sequential anaerobic and aerobic treatment in two steps bioreactor was performed for removal of colour in the pulp and paper mill effluent. In anaerobic treatment, colour (70%), lignin (25%), COD (42%), AOX (15%) and phenol (39%) were reduced in 15 days. The anaerobically treated effluent was separately applied in bioreactor in presence of fungal strain, Paecilomyces sp., and bacterial strain, Microbrevis luteum. Data of study indicated reduction in colour (95%), AOX (67%), lignin (86%), COD (88%) and phenol (63%) by Paecilomyces sp. where as M. luteum showed removal in colour (76%), lignin (69%), COD (75%) AOX (82%) and phenol (93%) by day third when 7 days anaerobically treated effluent was further treated by aerobic microorganisms. Change in pH of the effluent, and increase in biomass of microorganisms substantiated results of the study, which was concomitant to the treatment method.  相似文献   

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