15,944 research outputs found
Tratamento anaeróbio de efluentes lÃquidos industriais: alguns pontos focais
Esta comunicação aborda os fundamentos bioquÃmicos e microbiológicos que condicionam a concepção de reactores anaeróbios para tratamento de efluentes lÃquidos industriais e, complementarmente, apresenta vários aspectos referentes ao projecto de sistemas anaeróbios indicando alguns factores da opção aerobiose/anaerobiose, principais tipos de reactores e uma menção a aplicações industriais conhecidas
Mass transfer coefficients within anaerobic biofilms effects of external liquid velocity
This work concerns mass transport in anaerobic biofilms, formed under upflow liquid
velocities similar to the prevailing conditions in anaerobic reactors used for wastewater treatment.
During biofilm formation under liquid velocities of 1.5 and 13.2 m/h, internal mass transfer coefficients
were routinely measured. Mass transfer coefficients attained pseudo steady-state values between 2-4 x 10ˉ³ m/h, no dependence being observed between bulk flow and internal mass transport rates.
However, a transient variation in the liquid velocity from 1.5 up to 13.2 m/h, imposed after the biofilm
had reached the steady-state, increased the internal mass transport by 20% on average. This result
suggests that periodic changes in the bulk fluid velocity can be used as a tool to increase the transport
of soluble substrates inside already formed biofilms, although the effect seems to be limited.Fundação para a Ciência e a Tecnologia (FCT) - PRAXIS XXI (2/2.1/BIO/37/94).
European Commission
Environmental technology education in Portugal : analysis and perspectives
The scope of the present communication is the current status of environmental engineering in
Portugal. The different approaches concerning the environmental engineering courses available at
undergraduate levels as well as some post-graduation studies are described. Furthermore, an analysis
based on strengths, weakness, opportunities and trend issues regarding the environmental engineering
profession in Portugal is presented
Search for associations containing young stars (SACY). V. Is multiplicity universal? Tight multiple systems
Context: Dynamically undisrupted, young populations of stars are crucial to
study the role of multiplicity in relation to star formation. Loose nearby
associations provide us with a great sample of close (150 pc) Pre-Main
Sequence (PMS) stars across the very important age range (5-70 Myr) to
conduct such research.
Aims: We characterize the short period multiplicity fraction of the SACY
(Search for Associations Containing Young stars) accounting for any
identifiable bias in our techniques and present the role of multiplicity
fractions of the SACY sample in the context of star formation.
Methods: Using the cross-correlation technique we identified double-lined
spectroscopic systems (SB2), in addition to this we computed Radial Velocity
(RV) values for our subsample of SACY targets using several epochs of FEROS and
UVES data. These values were used to revise the membership of each association
then combined with archival data to determine significant RV variations across
different data epochs characteristic of multiplicity; single-lined multiple
systems (SB1).
Results: We identified 7 new multiple systems (SB1s: 5, SB2s: 2). We find no
significant difference between the short period multiplicity fraction
() of the SACY sample and that of nearby star forming regions
(1-2 Myr) and the field (10%) both as a function of
age and as a function of primary mass, , in the ranges [1:200 day] and
[0.08 -].
Conclusions: Our results are consistent with the picture of universal star
formation, when compared to the field and nearby star forming regions (SFRs).
We comment on the implications of the relationship between increasing
multiplicity fraction with primary mass, within the close companion range, in
relation to star formation.Comment: 14 pages, 18 figures, published, A&A
http://dx.doi.org/10.1051/0004-6361/20142385
Fate of protozoa during the start-up of a sequencing batch biofilm reactor used for the degradation of hydrocarbons
Large amounts of oily sludges are retained in patrol stations by gravity interceptors in order to prevent
their discharge in surface waters. Those residues are mainly composed of a mixture of hydrocarbons,
water and inert solids. Therefore, their final disposal represents a significant environmental problem. This
work concerns the study of microfauna biomass during the start-up of a SBBR designed for the treatment
of hydrocarbon slurries retained in an API oil separator. The findings of this study suggest that protozoal
colonization of the SBBR followed the same pattern of activated sludge systems, the free swimming and
crawling ciliates, and also fagellates being the dominant protozoa group during the star-up period of the
reactor. When the plant performance dropped, the number of flagellated protozoa rapidly increased, and a
concomitant decrease in the ciliated population was observed.Fundação para a Ciência e a Tecnologia (FCT)
Effect of the surfactants tween 20 and CTAB on fluoranthene and anthracene degradation by P. putida
The effect of a nonionic and a cationic surfactant, Tween 20 and CTAB, on the
biodegradation rate of fluoranthene and anthracene by a P. putida strain was
investigated. Tween 20 had a positive effect on the biodegradation rate of anthracene.
However, it did not affect significantly fluoranthene oxidation. The cationic surfactant
CTAB inhibited the oxidation of both PAHs, fluoranthene and anthracene
Search for associations containing young stars (SACY). VI. Is multiplicity universal? Stellar multiplicity in the range 3-1000 au from adaptive-optics observations
Context. Young loose nearby associations are unique samples of close (<150
pc), young (approx 5-100 Myr) pre-main sequence (PMS) stars. A significant
number of members of these associations have been identified in the SACY
collaboration. We can use the proximity and youth of these members to
investigate key ingredients in star formation processes, such as multiplicity.
Aims. We present the statistics of identified multiple systems from 113
confirmed SACY members. We derive multiplicity frequencies, mass-ratio, and
physical separation distributions in a consistent parameter space, and compare
our results to other PMS populations and the field.
Methods. We have obtained adaptive-optics assisted near-infrared observations
with NACO (ESO/VLT) and IRCAL (Lick Observatory) for at least one epoch of all
113 SACY members. We have identified multiple systems using co-moving
proper-motion analysis and using contamination estimates. We have explored
ranges in projected separation and mass-ratio of a [3-1000 au], and q [0.1-1],
respectively.
Results. We have identified 31 multiple systems (28 binaries and 3 triples).
We derive a multiplicity frequency (MF) of MF_(3-1000au)=28.4 +4.7, -3.9% and a
triple frequency (TF) of TF_(3-1000au)=2.8 +2.5, -0.8% in the separation range
of 3-1000 au. We do not find any evidence for an increase in the MF with
primary mass. The estimated mass-ratio of our statistical sample (with
power-law index gamma=-0.04 +/- 0.14) is consistent with a flat distribution
(gamma = 0).
Conclusions. We show further similarities (but also hints of discrepancies)
between SACY and the Taurus region: flat mass-ratio distributions and
statistically similar MF and TF values. We also compared the SACY sample to the
field (in the separation range of 19-100 au), finding that the two
distributions are indistinguishable, suggesting a similar formation mechanism.Comment: 16 Pages, accepted in A&A 28 May 201
Search for associations containing young stars (SACY) VII. New stellar and substellar candidate members in the young associations
The young associations offer us one of the best opportunities to study the
properties of young stellar and substellar objects and to directly image
planets thanks to their proximity (200 pc) and age (5-150 Myr).
However, many previous works have been limited to identifying the brighter,
more active members (1 M) owing to photometric survey
sensitivities limiting the detections of lower mass objects. We search the
field of view of 542 previously identified members of the young associations to
identify wide or extremely wide (1000-100,000 au in physical separation)
companions. We combined 2MASS near-infrared photometry (, , ) with
proper motion values (from UCAC4, PPMXL, NOMAD) to identify companions in the
field of view of known members. We collated further photometry and spectroscopy
from the literature and conducted our own high-resolution spectroscopic
observations for a subsample of candidate members. This complementary
information allowed us to assess the efficiency of our method. We identified 84
targets (45: 0.2-1.3 M, 17: 0.08-0.2 M, 22: 0.08 M)
in our analysis, ten of which have been identified from spectroscopic analysis
in previous young association works. For 33 of these 84, we were able to
further assess their membership using a variety of properties (X-ray emission,
UV excess, H, lithium and K I equivalent widths, radial velocities,
and CaH indices). We derive a success rate of 76-88% for this technique based
on the consistency of these properties. Once confirmed, the targets identified
in this work would significantly improve our knowledge of the lower mass end of
the young associations. Additionally, these targets would make an ideal new
sample for the identification and study of planets around nearby young stars.Comment: 28 pages, 24 figures, accepted in A&
Remoção de DQO, nitrogênio e sólidos de reator de lodos ativados no pós-tratamento de dejetos de suÃnos.
Projeto/Plano de Ação: 02.07.60.700-0
- …