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1.
Liping Huang Jingwen Chen Xie Quan Fenglin Yang 《Bioprocess and biosystems engineering》2010,33(8):937-945
Enhancement of Cr (VI) reduction rate and power production from biocathode microbial fuel cells (MFCs) was achieved using
indigenous bacteria from Cr (VI)-contaminated site as inoculum and MFC architecture with a relatively large cathode-specific
surface area of 340–900 m2 m−3. A specific Cr (VI) reduction rate of 2.4 ± 0.2 mg g−1VSS h−1 and a power production of 2.4 ± 0.1 W m−3 at a current density of 6.9 A m−3 were simultaneously achieved at an initial Cr (VI) concentration of 39.2 mg L−1. Initial Cr (VI) concentration and solution conductivity affected Cr (VI) reduction rate, power production and coulombic
efficiency. These findings demonstrate the importance of inoculation and MFC architecture in the enhancement of Cr (VI) reduction
rate and power production. This study is a beneficial attempt to improve the efficiency of biocathode MFCs and provide a good
candidate of bioremediation process for Cr (VI)-contaminated sites. 相似文献
2.
Evaluation of the bioremoval of Cr(VI) and TOC in biofilters under continuous operation using response surface methodology 总被引:1,自引:0,他引:1
In the present study, the bioremoval of Cr(VI) and the removal of total organic carbon (TOC) were achieved with a system composed
by an anaerobic filter and a submerged biofilter with intermittent aeration using a mixed culture of microorganisms originating
from contaminated sludge. In the aforementioned biofilters, the concentrations of chromium, carbon, and nitrogen were optimized
according to response surface methodology. The initial concentration of Cr(VI) was 137.35 mg l−1, and a bioremoval of 85.23% was attained. The optimal conditions for the removal of TOC were 4 to 8 g l−1 of sodium acetate, >0.8 g l−1 of ammonium chloride and 60 to 100 mg l−1 of Cr(VI). The results revealed that ammonium chloride had the strongest effect on the TOC removal, and 120 mg l−1 of Cr(VI) could be removed after 156 h of operation. Moreover, 100% of the Cr(VI) and the total chromium content of the aerobic
reactor output were removed, and TOC removals of 80 and 87% were attained after operating the anaerobic and aerobic reactors
for 130 and 142 h, respectively. The concentrations of cells in both reactors remained nearly constant over time. The residence
time distribution was obtained to evaluate the flow through the bioreactors. 相似文献
3.
Anaerobic bacteria that reduce hexavalent chromium [Cr(VI)] to trivalent [Cr(III)] are common in soils and were used to develop
a bioprocess employing a selection strategy. Indigenous Cr(VI)-reducers were enriched from Cr(VI)-contaminated soil under
anaerobic conditions. The mixed culture was then tested for Cr(VI)-reducing activity in a chemostat, followed by transfer
to a 1-L packed-bed bioreactor operated at 30°C for additional study. The support material used in the reactor consisted
of 6-mm porcelain saddles. Cr(VI) concentrations in the liquid ranged from 140–750 mg L−1. Cr(VI)-reducing bacteria were the dominant population with Cr(VI)-reduction rates of approximately 0.71 mg g−1 dry cells h−1 achieved at Cr(VI) concentrations of 750 mg L−1. These results indicate a potential for selecting and maintaining indigenous Cr(VI)-reducers in a bioreactor for Cr(VI)-remediation
of groundwater or soil wash effluents.
Received 09 January 1996/ Accepted in revised form 15 November 1996 相似文献
4.
The objective of this study was to improve the biological water–gas shift reaction for producing hydrogen (H2) by conversion of carbon monoxide (CO) using an anaerobic thermophilic pure strain, Carboxydothermus hydrogenoformans. Specific hydrogen production rates and yields were investigated at initial biomass densities varying from 5 to 20 mg volatile
suspended solid (VSS) L−1. Results showed that the gas–liquid mass transfer limits the CO conversion rate at high biomass concentrations. At 100-rpm
agitation and at CO partial pressure of 1 atm, the optimal substrate/biomass ratio must exceed 5 mol CO g−1 biomass VSS in order to avoid gas–liquid substrate transfer limitation. An average H2 yield of 94 ± 3% and a specific hydrogen production rate of ca. 3 mol g−1 VSS day−1 were obtained at initial biomass densities between 5 and 8 mg VSS−1. In addition, CO bioconversion kinetics was assessed at CO partial pressure from 0.16 to 2 atm, corresponding to a dissolved
CO concentration at 70°C from 0.09 to 1.1 mM. Specific bioactivity was maximal at 3.5 mol CO g−1 VSS day−1 for a dissolved CO concentration of 0.55 mM in the culture. This optimal concentration is higher than with most other hydrogenogenic
carboxydotrophic species. 相似文献
5.
The effect of three different types of glycerol on the performance of up-flow anaerobic sludge blanket (UASB) reactors treating
potato processing wastewater was investigated. High COD removal efficiencies were obtained in both control and supplemented
UASB reactors (around 85%). By adding 2 ml glycerol product per liter of raw wastewater, the biogas production could be increased
by 0.74 l biogas ml−1 glycerol product, which leads to energy values in the range of 810–1270 kWhelectric per m3 product. Moreover, a better in-reactor biomass yield was observed for the supplemented UASB reactor (0.012 g VSS g−1 CODremoved) compared to the UASB control (0.002 g VSS g−1 CODremoved), which suggests a positive effect of glycerol on the sludge blanket growth. 相似文献
6.
Okeke BC 《Journal of industrial microbiology & biotechnology》2008,35(12):1571-1579
Pollution of terrestrial surfaces and aquatic systems by hexavalent chromium, Cr(VI), is a worldwide public health problem.
A chromium resistant bacterial isolate identified as Exiguobacterium sp. GS1 by 16S rRNA gene sequencing displayed high rate of removal of Cr(VI) from water. Exiguobacterium sp. GS1 is 99% identical to Exiguobacterium acetylicum. The isolate significantly removed Cr(VI) at both high and low concentrations (1–200 μg mL−1) within 12 h. The Michaelis–Menten K
m
and V
max for Cr(VI) bioremoval were calculated to be 141.92 μg mL−1 and 13.22 μg mL−1 h−1, respectively. Growth of Exiguobacterium sp. GS1 was indifferent at 1–75 μg mL−1 Cr(VI) in 12 h. At initial concentration of 8,000 μg L−1, Exiguobacterium sp. GS1 displayed rapid bioremoval of Cr(VI) with over 50% bioremoval in 3 h and 91% bioremoval in 8 h. Kinetic analysis
of Cr(VI) bioremoval rate revealed zero-order in 8 h. Exiguobacterium sp. GS1 grew and significantly reduced Cr(VI) in cultures containing 1–9% salt indicating high salt tolerance. Similarly
the isolate substantially reduced Cr(VI) over a wide range of temperature (18–45 °C) and initial pH (6.0–9.0). The T
opt and initial pHopt were 35–40 °C and 7–8, respectively. Exiguobacterium sp. GS1 displayed a great potential for bioremediation of Cr(VI) in diverse complex environments. 相似文献
7.
Summary A tropical white-rot basidiomycete, BDT-14 (DSM 15396) was investigated for its chromium (VI) biosorption potential from an
aqueous solution. Pre-treatment of fungal biomass with acid resulted in 100% metal adsorption compared to only 26.64% adsorption
without any pre-treatment. Chromium adsorption was a rapid process at early exposure resulting in 60% chromium removal within
the first 2 h of exposure. An increase in biomass showed an increase in the total metal ions adsorption but a decrease in
specific uptake of metal ions. The concentrations of chromium had a pronounced effect on the rate of adsorption. The adsorption
efficiency was 100% when the initial Cr (VI) concentration was 100 mg l−1 with 1,000 mg biomass. Only 47.5% adsorption was observed with 500 mg l−1 Cr (VI) concentration. The adsorption data fit well with the Langmuir and Freundlich isotherm models. Comprehensive characterization
of parameters indicates BDT−14 biomass as a promising material for Cr (VI) adsorption. 相似文献
8.
The combined effect of phenanthrene and Cr(VI) on soil microbial activity, community composition and on the efficiency of
bioremediation processes has been studied. Biometer flask systems and soil microcosm systems contaminated with 2,000 mg of
phenanthrene per kg of dry soil and different Cr(VI) concentrations were investigated. Temperature, soil moisture and oxygen
availability were controlled to support bioremediation. Cr(VI) inhibited the phenanthrene mineralization (CO2 production) and cultivable PAH degrading bacteria at levels of 500–2,600 mg kg−1. In the bioremediation experiments in soil microcosms the degradation of phenanthrene, the dehydrogenase activity and the
increase in PAH degrading bacteria counts were retarded by the presence of Cr(VI) at all studied concentrations (25, 50 and
100 mg kg−1). These negative effects did not show a correlation with Cr(VI) concentration. Whereas the presence of Cr(VI) had a negative
effect on the phenanthrene elimination rate, co-contamination with phenanthrene reduced the residual Cr(VI) concentration
in the water exchangeable Cr(VI) fraction (WEF) in comparison with the soil microcosm contaminated only with Cr(VI). Clear
differences were found between the denaturing gradient gel electrophoresis (DGGE) patterns of each soil microcosm, showing
that the presence of different Cr(VI) concentrations did modulate the community response to phenanthrene and caused perdurable
changes in the structure of the microbial soil community. 相似文献
9.
A novel bacterium, Cr-10, was isolated from a chromium-contaminated site and capable of removing toxic chromium species from
solution by reducing hexavalent chromium to an insoluble precipitate. Sequence analysis of 16S rRNA gene of strain Cr-10 showed
that it was most closely related to Serratia rubidaea JCM 1240T (97.68%). Physiological and chemotaxonomic data also supported that strain Cr-10 was identified as Serratia sp., a genus which was never specially reported chromate-resistant before. Serratia sp., Cr-10 was tolerant to a concentration of 1,500 mg Cr(VI) L−1, which was the highest level reported until now. The optimum pH and temperature for reduction of Cr(VI) by Serratia sp. Cr-10 were found to be 7.0 and 37 °C, respectively. The Cr(VI) reduction was significantly influenced by additional carbon
sources, and among them fructose and lactose offered maximum reduction, with a rate of 0.28 and 0.25 mg Cr(VI) L−1 h−1, respectively. The cell-free extracts and filtrate of the culture were able to reduce Cr(VI) while concentration of total
chromium remained stable in the process, indicating that the enzyme-catalyzed mechanism was applied in Cr(VI) reduction by
the isolate. Additionally, it was found that there was hardly any chromium on the cell surface of the strain, further supporting
that reduction, rather than bioadsorption, plays a major role in the Cr(VI) removal. 相似文献
10.
Xu L Luo M Yang L Wei X Lin X Liu H 《Journal of industrial microbiology & biotechnology》2011,38(10):1709-1718
Cr(VI) was efficiently reduced to Cr(III) by Pannonibacter phragmitetus LSSE-09 encapsulated in liquid-core alginate–carboxymethyl cellulose capsules under alkaline conditions. Taking into account
the physical properties of the capsules, the activity of encapsulated cells, and total Cr(III) concentration in the supernatant,
optimal conditions (0.5% w/v sodium alginate; 2% w/v sodium carboxymethyl cellulose; 0.1 M CaCl2; 30-min gelation time) for LSSE-09 encapsulation were determined. At optimal conditions, a relatively high reduction rate
of 4.20 mg g(dry weight)−1 min−1 was obtained. Total Cr(III) concentration in the supernatant was significantly decreased after reduction, because 63.7% of
the formed soluble organo-Cr(III) compounds compared with those of free cells were captured by the relatively smaller porous
structure of alginate capsules. The optimal pH value (9.0) for Cr(VI) reduction was not changed after encapsulation. In addition,
encapsulated LSSE-09 showed no appreciable loss in activity after eight repeated cycles at 37°C, and 85.7% of its initial
activity remained after 35-day storage at 4°C. The results suggest that encapsulated LSSE-09 in alginate–carboxymethyl cellulose
capsules has potential biotechnological applications for the detoxification of Cr(VI)-contaminated wastewater. 相似文献
11.
Chromium(VI) resistance and removal by <Emphasis Type="Italic">Acinetobacter haemolyticus</Emphasis>
Quek Hsiao Pei Shafinaz Shahir A. S. Santhana Raj Zainul Akmar Zakaria Wan Azlina Ahmad 《World journal of microbiology & biotechnology》2009,25(6):1085-1093
The present work highlighted the studies on Cr(VI) reduction by cells of Acinetobacter haemolyticus (A. haemolyticus). The strain tolerated 90 mg Cr(VI) l−1 in LB broth compared to only 30 mg Cr(VI) l−1 in LB agar. From the FTIR analysis, the Cr(III) species formed was also most likely to form complexes with carboxyl, hydroxyl,
and amide groups from the bacteria. A TEM study showed the absence of precipitates on the cell wall region of the bacteria.
Instead, microprecipitates were observed in the cytoplasmic region of the cells, suggesting the transportation of Cr(VI) into
the cells. Intracellular reduction of Cr(VI) was supported by a reductase test using soluble crude cell-free extracts. The
specific reductase activity obtained was 0.52 μg Cr(VI) reduced per mg of protein an hour at pH 7.2 and 37°C. Our results
indicated that A. haemolyticus can be used as a promising microorganism for Cr(VI) reduction from industrial wastewaters. 相似文献
12.
A hexavalent chromium [Cr(VI)] reducing bacterial strain was isolated from chromium-containing slag. It was identified as
Pannonibacter phragmitetus based on physiological, biochemical characteristics and 16S rRNA gene sequence analysis. This bacterium displayed great Cr(VI)
reduction capability. The Cr(VI) could be completely removed in 24 h under anaerobic condition when the initial concentration
was 1,917 mg L−1, with the maximum reduction rate of 562.8 mg L−1 h−1. The Cr(VI) reduction rate increased with the increase of Cr(VI) concentration. P. phragmitetus was able to use many carbon sources such as lactose, fructose, glucose, pyruvate, citrate, formate, lactate, NADPH and NADH
as electron donors, among which the lactate had the greatest power to promote the reduction process. Zn2+, Cd2+ and Ni2+ inhibited, while Cu2+, Pb2+, Mn2+ and Co2+ stimulated the reduction. The optimum pH and temperature for reduction were 9.0 and 30 °C, respectively. The results indicated
that this strain had great potential for application in the bioremediation of chromate-polluted soil and water systems. 相似文献
13.
Kinetic analysis on the two-step processes of AOB and NOB in aerobic nitrifying granules 总被引:1,自引:0,他引:1
Fang Fang Bing-Jie Ni Xiao-Yan Li Guo-Ping Sheng Han-Qing Yu 《Applied microbiology and biotechnology》2009,83(6):1159-1169
Complete granulation of nitrifying sludge was achieved in a sequencing batch reactor. For the granular sludge, batch experiments
were conducted to characterize the kinetic features of ammonia oxidizers (AOB) and nitrite oxidizers (NOB) in the granules
using the respirometric method. A two-step nitrification model was established to determine the kinetic parameters of both
AOB and NOB. In addition to nitrification reactions, the new model also took into account biomass maintenance and mass transfer
through the granules. The yield coefficient, maximum specific growth rate, and affinity constant for ammonium for AOB were
0.21 g chemical oxygen demand (COD) g−1 N, 0.09 h−1, and 9.1 mg N L−1, respectively, whereas the corresponding values for NOB were 0.05 g COD g−1 N, 0.11 h−1, and 4.85 mg N L−1, respectively. The model developed in this study performed well in simulating the oxygen uptake rate and nitrogen conversion
kinetics and in predicting the oxygen consumption of the AOB and NOB in aerobic granules. 相似文献
14.
Bacterial consortium-AIE2 with a capability of contemporaneous Cr(VI) reduction and azo dye RV5 decolourization was developed
from industrial wastewaters by enrichment culture technique. The 16S rRNA gene based molecular analyses revealed that the
consortium bacterial community structure consisted of four bacterial strains namely, Alcaligenes sp. DMA, Bacillus sp. DMB, Stenotrophomonas sp. DMS and Enterococcus sp. DME. Cumulative mechanism of Cr(VI) reduction by the consortium was determined using in vitro Cr(VI) reduction assays.
Similarly, the complete degradation of Reactive Violet 5 (RV5) dye was confirmed by FTIR spectroscopic analysis. Consortium-AIE2
exhibited simultaneous bioremediation efficiencies of (97.8 ± 1.4) % and (74.1 ± 1.2) % in treatment of both 50 mg l−1 Cr(VI) and RV5 dye concentrations within 48 h of incubation at pH 7 and 37°C in batch systems. Continuous bioreactor systems
achieved simultaneous bioremediation efficiencies of (98.4 ± 1.5) % and (97.5 ± 1.4) % after the onset of steady-state at
50 mg l−1 input Cr(VI) and 25 mg l−1 input RV5 concentrations, respectively, at medium dilution rate (D) of 0.014 h−1. The 16S rRNA gene copy numbers in the continuous bioreactor as determined by real-time PCR assay indicated that Alcaligenes sp. DMA and Bacillus sp. DMB dominated consortium bacterial community during the active continuous bioremediation process. 相似文献
15.
Didem Güven Özgül Kutlu Güçlü İnsel Seval Sözen 《Bioprocess and biosystems engineering》2009,32(5):655-661
In this study, the ammonia removal efficiency for high ammonia-containing wastewaters was evaluated via partial nitrification.
A nitrifier biocommunity was first enriched in a fill-and-draw batch reactor with a specific ammonium oxidation rate of 0.1 mg NH4
−-N/mg VSS.h. Partial nitrification was established in a chemostat at a hydraulic retention time (HRT) of 1.15 days, which
was equal to the sludge retention time (SRT). The results showed that the critical HRT (SRT) was 1.0 day for the system. A
maximum specific ammonium oxidation rate was achieved as 0.280 mg NH4
−-N/mg VSS.h, which is 2.8-fold higher than that obtained in the fill-and-draw reactor, indicating that more adaptive and highly
active ammonium oxidizers were enriched in the chemostat. Dynamic modeling of partial nitrification showed that the maximum
growth rate for ammonium oxidizers was found to be 1.22 day−1. Modeling studies also validated the recovery period as 10 days. 相似文献
16.
Yasmin Khambhaty Kalpana Mody Shaik Basha Bhavanath Jha 《World journal of microbiology & biotechnology》2009,25(8):1413-1421
The removal of hexavalent chromium from aqueous solution was studied in batch experiments using dead biomass of three different
species of marine Aspergillus after alkali treatment. All the cultures exhibited potential to remove Cr(VI), out of which, Aspergillus niger was found to be the most promising one. This culture was further studied employing variation in pH, temperature, metal ion
concentration and biomass concentration with a view to understand the effect of these parameters on biosorption of Cr(VI).
Higher biosorption percentage was evidenced at lower initial concentration of Cr(VI) ion, while the sorption capacity of the
biomass increased with rising concentration of ions. Biomass as low as 0.8 g l−1 could biosorb 95% Cr(VI) ions within 2,880 min from an aqueous solution of 400 mg l−1 Cr(VI) concentration. Optimum pH and temperature for Cr(VI) biosorption were 2.0 and 50°C, respectively. Kinetic studies
based on pseudo second order models like Sobkowsk and Czerwinski, Ritchie, Blanchard and Ho and Mckay rate expressions have
also been carried out. The nature of the possible cell–metal ion interactions was evaluated by FTIR, SEM and EDAX analysis. 相似文献
17.
Vatsouria A Vainshtein M Kuschk P Wiessner A D K Kaestner M 《Journal of industrial microbiology & biotechnology》2005,32(9):409-414
Industrial wastewater is often polluted by Cr(VI) compounds, presenting a serious environmental problem. This study addresses
the removal of toxic, mutagenic Cr(VI) by means of microbial reduction to Cr(III), which can then be precipitated as oxides
or hydroxides and extracted from the aquatic system. A strain of Staphylococcus epidermidis L-02 was isolated from a bacterial consortium used for the remediation of a chromate-contaminated constructed wetland system.
This strain reduced Cr(VI) by using pyruvate as an electron donor under anaerobic conditions. The aims of the present study
were to investigate the specific rate of Cr(VI) reduction by the strain L-02, the effects of chromate and nitrate (available
as electron acceptors) on the strain, and the interference of chromate and nitrate reduction processes. The presence of Cr(VI)
decreased the growth rate of the bacterium. Chromate and nitrate reduction did not occur under sterile conditions but was
observed during tests with the strain L-02. The presence of nitrate increased both the specific Cr(VI) reduction rate and
the cell number. Under denitrifying conditions, Cr(VI) reduction was not inhibited by nitrite, which was produced during nitrate
reduction. The average specific rate of chromate reduction reached 4.4 μmol Cr 1010 cells−1 h−1, but was only 2.0 μmol Cr 1010 cells−1 h−1 at 20 °C. The maximum specific rate was as high as 8.8–9.8 μmol Cr 1010 cells−1 h−1. The role of nitrate in chromate reduction is discussed. 相似文献
18.
Mechanical shear contributes to granule formation resulting in quick start-up and stability of a hybrid anammox reactor 总被引:1,自引:0,他引:1
It appears that if suspended biomass washout can be reduced effectively, granule formation will be fastened in fluidized bed.
Quicker reactor start-up can be anticipated especially for those system keeping slow growth bacteria such as anammox. A hybrid
reactor combined fixed-bed with nonwoven fabrics as biomass carrier and fluidized bed with slow speed mechanical stirring
was therefore developed, and its nitrogen removal performances was evaluated experimentally. Only in 38 days, the total nitrogen
removal rate (NRR) reached to 1.9 kg(N) m−3 day−1 and then doubled within 17 days, with total nitrogen removal efficiency kept above 70%. After 180 days reactor operating,
the NRR reached a maximum value of 6.6 kg(N) m−3 day−1 and the specific anammox activity was gradually constant in 0.32 kg(N) kg(VSS)−1 day−1. Biomass attached on nonwoven fabrics could additionally improve reactor nitrogen removal by 8%. The dominant size of granular
sludge reached to 0.78 mm with stirring speed adjusted from 30 to 80 rpm and the hydraulic retention time (HRT) from 8 to
1.5 h during the whole operating time. Scanning electron microscope observation showed especially compact structure of granular
sludge. A 70% of anammox bacteria percentage was identified by fluorescence in situ hybridization analysis. 相似文献
19.
Adsorption and decolorization kinetics of methyl orange (MO) by anaerobic sludge in anaerobic sequencing batch reactors were
investigated. The anaerobic sludge was found to have a saturated adsorption capacity of 36 ± 1 mg g MLSS−1 to MO. UV/visible spectrophotometer and high-performance liquid chromatography analytical results indicated that the MO adsorption
and decolorization occurred simultaneously in this system. This process at various substrate concentrations could be well
simulated using a modified two-stage model with apparent pseudo first-order kinetics. Furthermore, a noncompetitive inhibition
kinetic model was also developed to describe the MO decolorization process at high NaCl concentrations, and an inhibition
constant of 3.67 g NaCl l−1 was estimated. This study offers an insight into the adsorption and decolorization processes of azo dyes by anaerobic sludge
and provides a better understanding of the anaerobic dye decolorization mechanisms. 相似文献
20.
Vandana Singh Premlata Kumari Sadanand Pandey Tripti Narayan 《Bioresource technology》2009,100(6):1977-1982
Using persulfate/ascorbic acid redox pair, poly(methylacrylate) was grafted on to guar gum and the conditions for the grafting were optimized. The copolymer sample having maximum %G was evaluated for the removal of Cr(VI) and the sorption conditions were optimized. The sorption was found pH dependent, pH 1.0 being the optimum value. Sorption data at pH 1.0 were modeled using both the Langmuir and Freundlich isotherms where the data fitted better to Freundlich isotherm. The equilibrium sorption capacity of 29.67 mg/g was determined from the Langmuir isotherm. The sorption followed a pseudo-second-order kinetics with a rate constant 2.5 × 10?4 g mg?1 min?1. The grafted product was also evaluated for Cr(VI) removal from local electroplating industrial waste water. The regeneration experiments revealed that the guar-graft-poly(methylacrylate) could be successfully reused for five cycles. In the present study conductivity measurements were used instead of conventional photometric method for determining Cr(VI) concentration in the equilibrium solutions and the results obtained have been compared with photometric method. Optimum Cr(VI) binding under highly acidic conditions indicated significant contribution of non electrostatic forces in the adsorption process. 相似文献