42 research outputs found
Impact of the hydraulic loading rate on the hydrodynamic characteristics of an anaerobic fixed bed reactor treating cattle slaughterhouse wastewater
The hydrodynamic behavior of an anaerobic fixed bed reactor (AFBR) was evaluated in the treatment of cattle slaughterhouse wastewater. The AFBR was operated at hydraulic retention time (HRT) of 14, 11 and 8 h. Stimulus-response assays were carried out with Eosin Y and the experimental data were adjusted to the single-parameter theoretical models of dispersion and N-continuous stirred tank reactors in series (N-CSTR). The experimental results of the residence time distribution curves showed that at lower flow rate, the reactor showed plug flow behavior with correlation coefficient (r) of 0.88 and number of dispersion of 0.2 for high dispersion (HD). However, at higher and intermediate flow rates, the AFBR behave as a complete mixture flow, (r) of 0.94 and 0.96, respectively. Residence time distribution curves in the AFBR showed a good approximation of the complete mixing model at hydraulic residence time of 11 and 8 h, with 5 and 2 N-CSTR reactors in series, respectively. The volume of dead zones corresponding to 43.0, 37.4 and 11.2% of the volume of the reactor for HRT of 14, 11 and 8 h, respectively, was noted, and hydraulic short circuiting were not confirmedinfo:eu-repo/semantics/publishedVersio
Graphene-Based Nanomaterials for Neuroengineering: Recent Advances and Future Prospective
Graphene unique physicochemical properties made it prominent among other allotropic forms of carbon, in many areas of research and technological applications. Interestingly, in recent years, many studies exploited the use of graphene family nanomaterials (GNMs) for biomedical applications such as drug delivery, diagnostics, bioimaging, and tissue engineering research. GNMs are successfully used for the design of scaffolds for controlled induction of cell differentiation and tissue regeneration. Critically, it is important to identify the more appropriate nano/bio material interface sustaining cells differentiation and tissue regeneration enhancement. Specifically, this review is focussed on graphene-based scaffolds that endow physiochemical and biological properties suitable for a specific tissue, the nervous system, that links tightly morphological and electrical properties. Different strategies are reviewed to exploit GNMs for neuronal engineering and regeneration, material toxicity, and biocompatibility. Specifically, the potentiality for neuronal stem cells differentiation and subsequent neuronal network growth as well as the impact of electrical stimulation through GNM on cells is presented. The use of field effect transistor (FET) based on graphene for neuronal regeneration is described. This review concludes the important aspects to be controlled to make graphene a promising candidate for further advanced application in neuronal tissue engineering and biomedical use
Dynamic changes in optical and chemical properties of tar ball aerosols by atmospheric photochemical aging
Following wood pyrolysis, tar ball aerosols were laboratory generated from
wood tar separated into polar and nonpolar phases. Chemical information of
fresh tar balls was obtained from a high-resolution time-of-flight aerosol
mass spectrometer (HR-ToF-AMS) and single-particle laser desorption/resonance
enhanced multiphoton ionization mass spectrometry (SP-LD-REMPI-MS). Their
continuous refractive index (RI) between 365 and 425 nm was retrieved using
a broadband cavity enhanced spectroscopy (BBCES). Dynamic changes in the
optical and chemical properties for the nonpolar tar ball aerosols in
NOx-dependent photochemical process were investigated in an
oxidation flow reactor (OFR). Distinct differences in the chemical
composition of the fresh polar and nonpolar tar aerosols were identified.
Nonpolar tar aerosols contain predominantly high-molecular weight
unsubstituted and alkyl-substituted polycylic aromatic hydrocarbons (PAHs),
while polar tar aerosols consist of a high number of oxidized aromatic
substances (e.g., methoxy-phenols, benzenediol) with higher O : C ratios
and carbon oxidation states. Fresh tar balls have light absorption
characteristics similar to atmospheric brown carbon (BrC) aerosol with higher
absorption efficiency towards the UV wavelengths. The average retrieved RI is
1.661+0.020i and 1.635+0.003i for the nonpolar and polar tar aerosols,
respectively, with an absorption Ångström exponent (AAE) between 5.7
and 7.8 in the detected wavelength range. The RI fits a volume mixing rule
for internally mixed nonpolar/polar tar balls. The RI of the tar ball
aerosols decreased with increasing wavelength under photochemical oxidation.
Photolysis by UV light (254 nm), without strong oxidants in the system,
slightly decreased the RI and increased the oxidation state of the tar balls.
Oxidation under varying OH exposure levels and in the absence of
NOx diminished the absorption (bleaching) and increased the
O : C ratio of the tar balls. The photobleaching via OH radical initiated
oxidation is mainly attributed to decomposition of chromophoric aromatics,
nitrogen-containing organics, and high-molecular weight components in the
aged particles. Photolysis of nitrous oxide (N2O) was used to
simulate NOx-dependent photochemical aging of tar balls in
the OFR. Under high-NOx conditions with similar OH exposure,
photochemical aging led to the formation of organic nitrates, and increased
both oxidation degree and light absorption for the aged tar ball aerosols.
These observations suggest that secondary organic nitrate formation
counteracts the bleaching by OH radical photooxidation to eventually regain
some absorption of the aged tar ball aerosols. The atmospheric implication
and climate effects from tar balls upon various oxidation processes are
briefly discussed.</p
Influence of recirculation rate on the performance of a combined anaerobic-aerobic reactor applied to the removal of carbon and nitrogen from poultry slaughterhouse wastewater
The objective of this study was to evaluate a combined anaerobic-aerobic upflow fixed-bed reactor with liquid phase recirculation for the removal of nitrogen and organic matter from poultry slaughterhouse wastewater. The reactor performance was evaluated with a hydraulic retention time (HRT) of 11 h and three different recirculation rates (R=0.5; 1 and 2). The highest nitrogen removal efficiency value was obtained with an HRT of 11 h (6.8 h in the anaerobic zone and 4.2 h in the aerobic zone) and a recirculation rate of 2. In this condition, the total nitrogen removal efficiency was 69%, with effluent concentrations of 6 mg NH4+ L-1 and 12 mg NO3- L-1. For all tested conditions, there was good chemical oxygen demand (COD) removal, with efficiency above 95%. The effect of dilution and the favoring of mass transfer caused by the increase in the recirculation rate positively influenced reactor performance.Key words: Anaerobic degradation, nitrification, denitrification, combined reactor
Kinetic behavior of nitrification in the post-treatment of poultry wastewater in a sequential batch reactor
A sequential batch reactor with suspended biomass and useful volume of 5 L was used in the removal of nutrients and organic matter in workbench scale under optimal conditions obtained by central composite rotational design (CCRD), with cycle time (CT) of 16 h (10.15 h, aerobic phase, and 4.35 h, anoxic phase) and carbon: nitrogen ratio (COD/NO2--N+NO3--N) equal to 6. Complete cycles (20), nitrification followed by denitrification, were evaluated to investigate the kinetic behavior of degradation of organic (COD) and nitrogenated (NH4+-N, NO2--N and NO3--N) matter present in the effluent from a bird slaughterhouse and industrial processing facility, as well as to evaluate the stability of the reactor using Shewhart control charts of individual measures. The results indicate means total inorganic nitrogen (NH4+-N+NO2- -N+NO3--N) removal of 84.32±1.59% and organic matter (COD) of 53.65±8.48% in the complete process (nitrification-denitrification) with the process under statistical control. The nitrifying activity during the aerobic phase estimated from the determination of the kinetic parameters had mean K1 and K2 values of 0.00381±0.00043 min-1 and 0.00381±0.00043 min-1, respectively. The evaluation of the kinetic behavior of the conversion of nitrogen indicated a possible reduction of CT in the anoxic phase, since removals of NO2--N and NO3--N higher than 90% were obtained with only 1 h of denitrification