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1.
During cassava starch production, large amounts of cyanoglycosides were released and hydrolysed by plant-borne enzymes, leading
to cyanide concentrations in the wastewater as high as 200 mg/l. For anaerobic degradation of the cyanide during pre-acidification
or single-step methane fermentation, anaerobic cultures were enriched from soil residues of cassava roots and sewage sludge.
In a pre-acidification reactor this culture was able to remove up to 4 g potassium cyanide/l of wastewater at a hydraulic
retention time (t
HR) of 4 days, equivalent to a maximal cyanide space loading of 400 mg CN− l−1 day−1. The residual cyanide concentration was 0.2–0.5 mg/l. Concentrated cell suspensions of the mixed culture formed ammonia and
formate in almost equimolar amounts from cyanide. Little formamide was generated by chemical decay. A concentration of up
to 100 mmol ammonia/l had no inhibitory effect on cyanide degradation. The optimal pH for cyanide degradation was 6–7.5, the
optimal temperature 25–37 °C. At a pH of 5 or lower, cyanide accumulated in the reactor and pre-acidification failed. The
minimal t
HR for continuous cyanide removal was 1.5 days. The enriched mixed culture was also able to degrade cyanide in purely mineralic
wastewater from metal deburring, either in a pre-acidification reactor with a two-step process or in a one-step methanogenic
reactor. It was necessary to supplement the wastewater with a carbon source (e.g. starch) to keep the population active enough
to cope with any possible inhibiting effect of cyanide.
Received: 29 April 1998 / Received revision: 8 June 1998 / Accepted: 14 June 1998 相似文献
2.
Removal of organic pollutants and of nitrate from wastewater from the dairy industry by denitrification 总被引:3,自引:0,他引:3
The aim of this work was to remove nitrate-N and organic pollutants from wastewater of the dairy industry by denitrification.
An artificially prepared wastewater, containing 250 mg/l nitrate-N and 1.5 g/l whey powder, was completely denitrified with
removal of 90%–93% of the chemical oxygen demand (COD) of the whey powder by suspended or immobilized mixed cultures and by
a suspended or immobilized pure culture that was isolated from the mixed culture inoculum. For the above COD/nitrate-N ratio
of 6:1, the results indicated that the organic compounds of the wastewater served as electron donors for complete denitrification
and that there was no need to add an external carbon source. In batch denitrification assays the suspended or immobilized
mixed cultures proved to be more active and reacted faster than the isolated pure cultures. In continuous denitrification
processes with immobilized pure or mixed cultures, the alginate beads, used for immobilization, were not stable for more than
12 days of incubation. The mixed free cultures removed the nitrate-N and COD continuously with no change of their activity
for at least 15 days at an optimum hydraulic retention time of 0.27 days with a loading rate of 900 mg nitrate-N l−1 day−1.
Received: 13 October 1997 / Received revision: 16 December 1997 / Accepted: 19 December 1997 相似文献
3.
The influence of ammonia on the anaerobic degradation of peptone by mesophilic and thermophilic populations of biowaste was
investigated. For peptone concentrations from 5 g l−1 to 20 g l−1 the mesophilic population revealed a higher rate of deamination than the thermophilic population, e.g. 552 mg l−1 day−1 compared to 320 mg l−1 day−1 at 10 g l−1 peptone. The final degree of deamination of the thermophilic population was, however, higher: 102 compared to 87 mg NH3/g peptone in the mesophilic cultures. If 0.5–6.5 g l−1 ammonia was added to the mesophilic biowaste cultures, deamination of peptone, degradation of its chemical oxygen demand
(COD) and formation of biogas were increasingly inhibited, but no hydrogen was formed. The thermophilic biowaste cultures
were most active if around 1 g ammonia l−1 was present. Deamination, COD degradation and biogas production decreased at lower and higher ammonia concentrations and
hydrogen was formed in addition to methane. Studies of the inhibition by ammonia of peptone deamination, COD degradation and
methane formation revealed a K
i (50%) for NH3 of 92, 95 and 88 mg l−1 at 37 °C and 251, 274 and 297 mg l−1 at 55 °C respectively. This indicated that the thermophilic flora tolerated significantly more NH3 than the mesophilic flora. In the mesophilic reactor effluent 4.6 × 108 peptone-degrading colony-forming units (cfu)/ml were culturable, whereas in the thermophilic reactor effluent growth of only
5.6 × 107 cfu/ml was observed.
Received: 24 April 1998 / Received revision: 26 June 1998 / Accepted: 27 June 1998 相似文献
4.
Thermophilic acidification of dairy wastewater 总被引:2,自引:0,他引:2
Acidification of simulated dairy wastewater was conducted in an upflow reactor at 55 °C. Results showed that the degree of
acidification decreased with the increase in chemical oxygen demand (COD) loading rate, from 60.8% at 4 g l−1 day−1 to 27.1% at 24 g l−1 day−1. Carbohydrate was readily degraded at all loading rates, but degradation of protein and lipid decreased with the increase
in loading rate. Most carbohydrate degradation occurred at the reactor bottom, whereas protein was degraded mainly after the
carbohydrate became depleted. The predominant acidification products were acetate, propionate, butyrate and ethanol, whereas
formate, i-butyrate, valerate, i-valerate, caproate, lactate, methanol, propanol and butanol were present in lesser quantities. The increase in loading rate
resulted in the increase of propionate and the decrease of acetate, but had little effect on ethanol and butyrate productions.
Only 2.5–8.8% of influent COD was converted to hydrogen and methane. The biomass yield was 0.30–0.43 mg VSS mg−1 COD.
Received: 8 December 1999 / Received revision: 14 February 2000 / Accepted: 25 February 2000 相似文献
5.
Our previous study showed that an activated-sludge process broke down at the phenol-loading rate of 1.5 g l−1 day−1, when non-flocculating bacteria (called R6T and R10) overgrew the sludge, resulting in a sludge washout. In this study, we
attempted to circumvent this breakdown problem by reclaiming the consortium structure. Activated sludge was fed phenol, and
the phenol-loading rate was increased stepwise from 0.5 g l−1 day−1 to 1.0 g l−1 day−1 and then to 1.5 g l−1 day−1. Either galactose or glucose (at 0.5 g l−1 day−1) was also supplied to the activated sludge from the phenol-loading rate of 1.0 g l−1 day−1. Pure culture experiments have suggested galactose to be a preferential substrate for a floc-forming bacterium (R6F) that
predominantly degrades phenol under low phenol-loading conditions. Supplying galactose allowed sustainment of the R6F population
and suppression of the overgrowth of R6T and R10 at the phenol-loading rate of 1.5 g l−1 day−1. This measure allowed the activated-sludge process to treat phenol at a phenol-loading rate up to 1.5 g l−1 day−1, although it broke down at 2.0 g l−1 day−1. In contrast, supplying glucose reduced the R6F population and allowed the activated-sludge process to break down at the
phenol-loading rate of 1.0 g l−1 day−1. This study demonstrated that reclamation of the activated-sludge consortium by selective biostimulation of the floc-forming
population improved the phenol-treating ability of the process.
Received: 13 January 2000 / Received revision: 10 March 2000 / Accepted: 7 April 2000 相似文献
6.
Biological treatment of drinking water is a cost-effective alternative to conventional physico/chemical processes. A new
concept was tested to overcome the main disadvantage of biological denitrification, the intensive post-treatment process to
remove microorganisms and remnant carbon source. The biological reaction zone and carbon supply were separated from the raw
water stream by a nitrate-permeable membrane. Denitrification takes place in a biofilm, which is immobilized at the membrane.
In a series of bench-scale runs, different types of membranes and reactor configurations were investigated. The best denitrification
rates achieved were 1230 mg NO3
−-N m−2 day−1. In one run, raw water containing 100 mg NO3
− l−1 was completely freed from nitrate. The membrane and the attached biofilm also represent a barrier against the passage of
the C source and nutrients into the raw water. At concentrations of 20 mg l−1 ethanol and 15 mg l−1 phosphate in the bioreactor no diffusion through the membrane into the treated water was observed. Without any post-treatment,
the effluent met nearly all the relevant criteria for drinking water; only the colony count was slightly increased.
Received: 18 December 1996 / Received last revision: 14 April 1997 / Accepted: 19 April 1997 相似文献
7.
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
8.
Removal of nitrate and phosphate ions from water, by using the thermophilic cyanobacterium Phormidium laminosum, immobilized on cellulose hollow fibres in the tubular photobioreactor at 43 °C, was studied by continuously supplying dilute
growth medium for 7 days and then secondarily treated sewage (STS) for 12 days. The concentrations of NO−
3 and PO3−
4 in the effluent from the dilute growth medium decreased from 5.0 mg N/l to 3.1 mg N/l, and from 0.75 mg P/l to 0.05 mg P/l
respectively, after a residence time of 12 h. The concentrations of NO−
3 and PO3−
4 in the effluent from STS decreased from 11.7 mg N/l to 2.0 mg N/l, and from 6.62 mg P/l to 0.02 mg P/l respectively, after
a residence time of 48 h. The removal rates of nitrogenous␣and phosphate ions from STS were 0.24 and 0.11 mmol day−1 l reactor−1 respectively, under the same conditions. Although, among nitrogenous ions, nitrate and ammonium ions were efficiently removed
by P.␣laminosum, the nitrite ion was released into the effluent when STS was used as influent. Treatment of water with thermophilic P. laminosum immobilized on hollow fibres thus appears to be an appropriate means for the removal of inorganic nitrogen and phosphorus
from treated wastewater.
Received: 15 August 1997 / Received last revision: 18 November 1997 / Accepted: 29 November 1997 相似文献
9.
Mesophilic and thermophilic anaerobic digestion of source-sorted organic wastes: effect of ammonia on glucose degradation and methane production 总被引:5,自引:0,他引:5
The wet organic fraction of household wastes was digested anaerobically at 37 °C and 55 °C. At both temperatures the volatile
solids loading was increased from 1 g l−1 day−1 to 9.65 g l−1 day−1, by reducing the nominal hydraulic retention time from 93 days to 19 days. The volatile solids removal in the reactors at
both temperatures for the same loading rates was in a similar range and was still 65% at 19 days hydraulic retention time.
Although more biogas was produced in the thermophilic reactor, the energy conservation in methane was slightly lower, because
of a lower methane content, compared to the biogas of the mesophilic reactor. The slightly lower amount of energy conserved
in the methane of the thermophilic digester was presumably balanced by the hydrogen that escaped into the gas phase and thus
was no longer available for methanogenesis. In the thermophilic process, 1.4 g/l ammonia was released, whereas in the mesophilic
process only 1 g/l ammonia was generated, presumably from protein degradation. Inhibition studies of methane production and
glucose fermentation revealed a K
i (50%) of 3 g/l and 3.7 g/l ammonia (equivalent to 0.22 g/l and 0.28 g/l free NH3) at 37 °C and a K
i (50%) of 3.5 g/l and 3.4 g/l ammonia (equivalent to 0.69 g/l and 0.68 g/l free NH3) at 55 °C. This indicated that the thermophilic flora tolerated at least twice as much of free NH3 than the mesophilic flora and, furthermore, that the thermophilic flora was able to degrade more protein. The apparent ammonia
concentrations in the mesophilic and in the thermophilic biowaste reactor were low enough not to inhibit glucose fermentation
and methane production of either process significantly, but may have been high enough to inhibit protein degradation. The
data indicated either that the mesophilic and thermophilic protein degraders revealed a different sensitivity towards free
ammonia or that the mesophilic population contained less versatile protein degraders, leaving more protein undegraded.
Received: 26 March 1997 / Received revision: 13 May 1997 / Accepted: 19 May 1997 相似文献
10.
A fluidized-bed reactor (FBR) was used to enrich an aerobic chlorophenol-degrading microbial culture. Long-term continuous-flow
operation with low effluent concentrations selected oligotrophic microorganisms producing good-quality effluent for pentachlorophenol(PCP)-contaminated
water. PCP biodegradation kinetics was studied using this FBR enrichment culture. The results from FBR batch experiments were
modeled using a modified Haldane equation, which resulted in the following kinetic constants: q
max = 0.41 mg PCP mg protein−1 day−1, K
S = 16 μg l−1, K
i = 5.3 mg l−1, and n = 3.5. These results show that the culture has a high affinity for PCP but is also inhibited by relatively low PCP concentrations
(above 1.1 mg PCP l−1). This enrichment culture was maintained over 1 year of continuous-flow operation with PCP as the sole source of carbon and
energy. During continuous-flow operation, effluent concentrations below 2 μg l−1 were achieved at 268 min hydraulic retention time (t
HR) and 2.5 mg PCP l−1 feed concentration. An increase in loading rate by decreasing t
HR did not significantly deteriorate the effluent quality until a t
HR decrease from 30 min to 21 min resulted in process failure. Recovery from process failure was slow. Decreasing the feed PCP
concentration and increasing t
HR resulted in an improved process recovery.
Received: 10 October 1996 / Received revision: 21 January 1997 / Accepted: 24 January 1997 相似文献
11.
Low-temperature bioremediation of a waste water contaminated with anionic surfactants and fuel oil 总被引:7,自引:0,他引:7
We conducted a laboratory study at 10 °C on the biological decontamination of the waste water from a garage and car-wash
that was contaminated with anionic surfactants (57 mg l−1) and fuel oil (184 mg hydrocarbons l−1). The indigenous microorganisms degraded both contaminants efficiently after biostimu- lation by an inorganic nutrient supply.
After 7 days at 10 °C, the residual contaminations were 11 mg anionic surfactants l−1 and 26 mg hydrocarbons l−1. After 35 days, only the anionic surfactants had been further reduced to 3 mg l−1. Bioaugmentation of the unfertilized waste water with a cold-adapted inoculum, able to degrade both hydrocarbons (diesel
oil) and anionic surfactants (sodium dodecyl sulphate), resulted in a significant increase of the hydrocarbon biodegradation
during the first 3 days of decontamination, whereas biodegradation of anionic surfactants was inhibited during the first 21 days
following inoculation. Bioaugmentation of the nutrient-amended waste water was without any effect.
Received: 14 November 1997 / Accepted: 29 November 1997 相似文献
12.
Inhibition of methane production from whey by heavy metals – protective effect of sulfide 总被引:1,自引:0,他引:1
A whey solution was used as a substrate for methane production in an anaerobic fixed-bed reactor. At a hydraulic retention
time of 10 days, equivalent to a space loading of 3.3 kg (m3 day)−1, 90% of the chemical oxygen demand was converted to biogas. Only a little propionate remained in the effluent. Toxicity tests
with either copper chloride, zinc chloride or nickel chloride were performed on effluent from the reactor. Fifty per cent
inhibition of methanogenesis was observed in the presence of ≥10 mg CuCl2 l−1≥40 mg ZnCl2 l−1 and ≥60 mg NiCl2 l−1, respectively. After exposure to Cu2+, Zn2+ or Ni2+ ions for 12 days, complete recovery of methanogenesis by equimolar sulfide addition was possible upon prolonged incubation.
Recovery failed, however, for copper chloride concentrations ≥40 mg l−1. If the sulfide was added simultaneously with the three heavy metal salts, methanogenesis was only slightly retarded and
the same amount of methane as in non-inhibited controls was reached either 1 day (40 mg ZnCl2 l−1) or 2 days later (10 mg CuCl2 l−1). Up to 60 mg NiCl2 l−1 had no effect if sulfide was present. Sulfide presumably precipitated the heavy metals as metal sulfides and by this means
prevented heavy metal toxicity.
Received: 8 October 1999 / Received revision: 3 January 2000 / Accepted: 4 January 2000 相似文献
13.
Aerobic biodegradation of gasoline and its constituents, benzene, toluene and ethylbenzene were studied by an enrichment
from soil indigenous microbial population. The enrichment culture completely degraded 16.1–660 mg/l gasoline in 2.5–16 days
respectively, without accumulation of any by-products. The kinetics of gasoline as well as benzene, toluene and ethylbenzene
biodegradation was investigated with initial gasoline concentrations of 16.1–62.6 mg/l. The maximum specific rates of biodegradation
of benzene, toluene and ethylbenzene were 0.12, 0.38 and 0.19 mg mg biomass−1 day−1 respectively. When benzene and toluene were used as sole substrate, the maximum specific rates of their biodegradation were
62.9 and 16.4 times greater than the corresponding values for a mixture (gasoline). The microbial culture was able to mineralize
up to 200 mg/l pure toluene and benzene. Maximum mineralization efficiencies of benzene and toluene were 76.7 ± 5.1% and 76.8 ± 1.3%
respectively. Self-inhibition and competitive inhibition patterns were observed during the biodegradation of benzene and toluene
alone and in the mixture respectively. The observed kinetics was modeled according to Andrews' inhibition model.
Received: 6 August 1997 / Received revision: 18 November 1997 / Accepted: 29 November 1997 相似文献
14.
E. Kostyál E.-L. Nurmiaho-Lassila J. A. Puhakka M. Salkinoja-Salonen 《Applied microbiology and biotechnology》1997,47(6):734-741
This study deals with combining the biologi cal removal of organic halogens with the removal of nitrogen from bleached kraft
pulp mill wastewater in fluidized-bed reactors under nitrifying and denitrifying conditions. Untreated and biotreated bleached
kraft pulp mill wastewaters had no detrimental effect on nitrification or denitrification. The nitrifying biofilm reactor,
pregrown on synthetic inorganic feed with ammonia, removed without a lag phase adsorbable organic halogens [7.2 mg Cl (g biomass
volatile solids)−1day−1] from bleached kraft pulp mill wastewater and selected chlorophenols from synthetic wastewater. Electron microscopical examination
of the biofilm showed that bacteria, morphologically similar to the nitrifying species Nitrosomonas or Nitrobacter, and Nitrosospira were dominant. The denitrifying fluidized-bed reactor, pregrown on nitrate and methanol, denitrified without a lag phase bleached
kraft pulp mill wastewater. Under denitrifying conditions, 35% of the total organic carbon content of untreated bleached kraft
pulp mill waste water was removed. The reducing power delivered by untreated bleached kraft pulp mill wastewater for denitrification
was 2 mmol electrons/mmol carbon mineralized. Dechlorination under denitrifying conditions was negligible.
Received: 21 November 1996 / Received revision: 27 January 1997 / Accepted: 1 February 1997 相似文献
15.
E. J. Olguín S. Galicia R. Camacho G. Mercado T. J. Pérez 《Applied microbiology and biotechnology》1997,48(2):242-247
The use of untreated sea water supplemented with anaerobic effluents from digested pig waste and sodium bicarbonate was evaluated
as a low-cost medium for semi-continuous cultivation of a mixed culture of two Spirulina strains in outdoor raceways under temperate climatic conditions (pond temperature in the range 21–26 °C and light intensity
in the range 225–957␣μE m−2 s−1). The mixed culture had a predominant population (86.6 ± 3.9%) of an atypical Spirulina strain consisting of straight filaments, which appeared spontaneously after the strain with helicoidal trichomes had been
subcultured. Morphological studies for the identification of the type and size of trichomes of the two strains (HF and SF)
were carried out. The proportions of the two strains were observed to be stable during the monitoring period (30 days). Three
different sets of semicontinuous cultures were carried out. Sets 1 and 2 were operated under regime 1 (a single addition of
anaerobic effluents at time zero and no pH control) during the same season (June and July) of different years. Set 3 was operated
under regime 2 (semi-continuous addition of anaerobic effluents and pH control) during the autumn. A minimum productivity
of 3.6 g m−2 day−1 was obtained at one of the lowest temperatures (22.1 °C) and light intensities (245 μE m−2 s−1) and a maximum productivity of 10.9 g m−2 day−1 was observed at the highest temperature (25 °C) and highest average light intensity (618 μE m−2 s−1) registered for sets 1 and 2. The protein content in the Spirulina biomass harvested from these two sets varied from 17% to 65.6%. In set 3, a maximum productivity of 9.0 g m−2 day−1 was recorded at an average temperature of 24.4 °C and at an average light intensity of 668 μE m−2 s−1. The protein content in this set under regime 2 varied within a narrower range than in set 1 and set 2 (from 34.8% to 49.1%),
apparently because of a continuous availability of ammonia nitrogen at a level of 30–50 mg l−1. However, in terms of the removal of ammonia nitrogen and chemical oxygen demand, regime 1 was more efficient than regime␣2.
Received: 3 September 1996 / Received revision: 19 February 1997 / Accepted: 7 March 1997 相似文献
16.
A sequencing batch reactor system for high-level biological nitrogen and phosphorus removal from abattoir wastewater 总被引:2,自引:0,他引:2
A sequencing batch reactor (SBR) system is demonstrated to biologically remove nitrogen, phosphorus and chemical oxygen demand
(COD) to very low levels from abattoir wastewater. Each 6 h cycle contained three anoxic/anaerobic and aerobic sub-cycles
with wastewater fed at the beginning of each anoxic/anaerobic period. The step-feed strategy was applied to avoid high-level
build-up of nitrate or nitrite during nitrification, and therefore to facilitate the creation of anaerobic conditions required
for biological phosphorus removal. A high degree removal of total phosphorus (>98%), total nitrogen (>97%) and total COD (>95%)
was consistently and reliably achieved after a 3-month start-up period. The concentrations of total phosphate and inorganic
nitrogen in the effluent were consistently lower than 0.2 mg P l−1 and 8 mg N l−1, respectively. Fluorescence in situ hybridization revealed that the sludge was enriched in Accumulibacter spp. (20–40%), a known polyphosphate accumulating organism, whereas the known glycogen accumulating organisms were almost
absent. The SBR received two streams of abattoir wastewater, namely the effluent from a full-scale anaerobic pond (75%) and
the effluent from a lab-scale high-rate pre-fermentor (25%), both receiving raw abattoir wastewater as feed. The pond effluent
contained approximately 250 mg N l−1 total nitrogen and 40 mg P l−1 of total phosphorus, but relatively low levels of soluble COD (around 500 mg l−1). The high-rate lab-scale pre-fermentor, operated at 37°C and with a sludge retention time of 1 day, proved to be a cheap
and effective method for providing supplementary volatile fatty acids allowing for high-degree of biological nutrient removal
from abattoir wastewater. 相似文献
17.
Bioconversion of (4R)-(+)-limonene to (4R)-(+)-α-terpineol by immobilized fungal mycelia of Penicillium digitatum was investigated in batch, repeated-batch and continuously fed systems. The fungi were immobilized in calcium alginate beads.
These beads remained active for at least 14 days when they were stored at 4 °C. Three different aeration rates were tested.
The highest yield was obtained at a dissolved oxygen level of 50.0 μmol/l. α-Terpineol production by this fungus was 12.83 mg
(g beads)−1 day−1, producing a 45.81% bioconversion of substrate. Repeated-batch bioconversion showed yield decreases in the second and the
third cycles. Regeneration with nutrient media after the third cycle improved the bioconversion yields. With continuous bioconversion,
the half-life was dependent on the aeration. The optimum conditions with a continuous reactor were at an aeration rate of
0.3 standard l/min and a dilution rate of 0.0144 h−1.
Received: 10 June 1997 / Received revision: 18 August 1997 / Accepted: 11 September 1997 相似文献
18.
A two-phase aqueous/organic partitioning bioreactor scheme was used to degrade mixtures of toluene and benzene, and toluene
and p-xylene, using simultaneous and sequential feeding strategies. The aqueous phase of the partitioning bioreactor contained
Pseudomonas sp. ATCC 55595, an organism able to degrade benzene, toluene and p-xylene simultaneously. An industrial grade of oleyl alcohol served as the organic phase. In each experiment, the organic
phase of the bioreactor was loaded with 10.15 g toluene, and either 2.0 g benzene or 2.1 g p-xylene. The resulting aqueous phase concentrations were 50 mg/l, 25 mg/l and 8 mg/l toluene, benzene and p-xylene respectively. The simultaneous fermentation of benzene and toluene consumed these compounds at volumetric rates of
0.024 g l−1 h−1 and 0.067 g l−1 h−1, respectively. The simultaneous fermentation of toluene and p-xylene consumed these xenobiotics at volumetric rates of 0.066 g l−1 h−1 and 0.018 g l−1 h−1, respectively. A sequential feeding strategy was employed in which toluene was added initially, but the benzene or p-xylene aliquot was added only after the cells had consumed half of the initial toluene concentration. This strategy was shown
to improve overall degradation rates, and to reduce the stress on the microorganisms. In the sequential fermentation of benzene
and toluene, the volumetric degradation rates were 0.056 g l−1 h−1 and 0.079 g l−1 h−1, respectively. In the toluene/p-xylene sequential fermentation, the initial toluene load was consumed before the p-xylene aliquot was consumed. After 12 h in which no p-xylene degradation was observed, a 4.0-g toluene aliquot was added, and p-xylene degradation resumed. Excluding that 12-h period, the microbes consumed toluene and p-xylene at volumetric rates of 0.074 g l−1 h−1 and 0.025 g l−1 h−1, respectively. Oxygen limitation occurred in all fermentations during the rapid growth phase.
Received: 16 November 1998 / Received revision: 29 March 1999 / Accepted: 9 April 1999 相似文献
19.
Lebeau T Gaudin P Junter GA Mignot L Robert JM 《Applied microbiology and biotechnology》2000,54(5):634-640
The marine diatom Haslea ostrearia was immobilized in a tubular agar gel layer introduced into a photobioreactor of original design with internal illumination
for the continuous synthesis of marennin, a blue-green pigment of biotechnological interest. Marennin was produced for a long-term
period (27–43 days) and the volumetric productivity was maximum (18.7 mg day−1 l−1 gel) at the highest dilution rate (0.25 day−1) and lowest agar layer thickness (3 mm). Heterogeneous cell distribution in the agar layer revealed diffusional limitation
of light and nutrients. However, the 3 mm gel thickness led to a more homogeneous cell distribution during incubation and
to an increase of the whole biomass in the agar gel layer.
Received: 22 October 1999 / Received revision: 14 February 2000 / Accepted: 18 February 2000 相似文献
20.
Bocher BT Agler MT Garcia ML Beers AR Angenent LT 《Journal of industrial microbiology & biotechnology》2008,35(5):321-329
Many beer breweries use high-rate anaerobic digestion (AD) systems to treat their soluble high-strength wastewater. Biogas
from these AD systems is used to offset nonrenewable energy utilization in the brewery. With increasing nonrenewable energy
costs, interest has mounted to also digest secondary residuals from the high-rate digester effluent, which consists of yeast
cells, bacteria, methanogens, and small (hemi)cellulosic particles. Mesophilic (37 °C) and thermophilic (55 °C) lab-scale,
low-rate continuously-stirred anaerobic digestion (CSAD) bioreactors were operated for 258 days by feeding secondary residuals
at a volatile solids (VS) concentration of ∼40 g l−1. At a hydraulic retention time (HRT) of 15 days and a VS loading rate of 2.7 g VS l−1 day−1, the mesophilic bioreactor showed an average specific volumetric biogas production rate of 0.88 l CH4 l−1 day−1 and an effluent VS concentration of 22.2 g VS l−1 (43.0% VS removal efficiency) while the thermophilic bioreactor displayed similar performances. The overall methane yield
for both systems was 0.21 l CH4 g−1 VS fed and 0.47–0.48 l CH4 g−1 VS removed. A primary limitation of thermophilic digestion of this protein-rich waste is the inhibition of methanogens due
to higher nondissociated (free) ammonia (NH3) concentrations under similar total ammonium (NH4
+) concentrations at equilibrium. Since thermophilic AD did not result in advantageous methane production rates or yields,
mesophilic AD was, therefore, superior in treating secondary residuals from high-rate AD effluent. An additional digester
to convert secondary residuals to methane may increase the total biogas generation at the brewery by 8% compared to just conventional
high-rate digestion of brewery wastewater alone.
JIMB-2008: BioEnergy—Special issue. 相似文献