Biomedical subjects

J M Lema

Publications and source records attributed to J M Lema.

At least 19 recordsLinked to original sources

PubMed2007

Dynamic modeling of an enzymatic membrane reactor for the treatment of xenobiotic compounds.

A membrane enzymatic reactor, consisting of a stirred tank coupled to an ultrafiltration membrane was set up for the enzymatic oxidation of xenobiotic compounds. The azo dye Orange II was selected for the model compound and manganese peroxidase for the oxidative enzyme. The ligninolytic cycle was initiated and maintained by the controlled addition of all factors (reactants, mediators, and stabilizers) at suitable rates. Considering the distinctiveness of this process, in which the substrate to be oxidized is not the primary substrate for the enzyme, a kinetic model was developed. The azo dye concentration and hydrogen peroxide addition rate were found to be the main factors affecting the process. The reaction kinetics was defined using a Michaelis-Menten model with respect to the Orange II concentration and a first-order linear dependence relative to the H(2)O(2) addition rate. The dynamic model, which takes into account both the kinetics and the hydraulics of the system, was validated by comparing the experimental results in continuous operation under steady and non-steady state to model predictions. In particular, the model predicted the behavior of the system when unexpected alterations in steady-state operation occurred. Furthermore, the model allowed us to obtain the most appropriate H(2)O(2)/Orange II ratio in the feed to maximize the process efficiency.

Azo Compounds↗

PubMed2006

Operation of a two-phase partitioning bioreactor for the oxidation of anthracene by the enzyme manganese peroxidase.

A study was conducted to determine the potential of a two-phase partitioning bioreactor (TPPB) for the treatment of a poorly soluble compound, anthracene, by the enzyme manganese peroxidase (MnP) from the fungus Bjerkandera sp. BOS55. Silicone oil was used as the immiscible solvent, which contained anthracene at high concentrations. The optimization of the oxidation process was conducted taking into account the factors which may directly affect the MnP catalytic cycle (the concentration of H(2)O(2) and malonic acid) and those that affect the mass transfer of anthracene between the organic and the aqueous phase (solvent and agitation speed). The main objective was carried out in terms of improved efficiency, i.e., maximizing the anthracene oxidized per unit of enzyme used. The TPPB reached nearly complete oxidation of anthracene at a conversion rate of 1.8mgl(-1)h(-1) in 56h, which suggests the application of enzymatic TPPBs for the removal of poorly soluble compounds.

Anthracenes↗

PubMed2006

Trials of bioremediation on a beach affected by the heavy oil spill of the Prestige.

The objective of this study was to assess the efficiency of several bioremediation products in accelerating the in situ biodegradation of the heavy fuel oil spill of the Prestige. Trials of bioremediation were conducted in sand, rocks and granite tiles on the beach of Sorrizo (A Coruña, NW Spain) that was polluted by the spill. Neither the added microorganisms nor the nutrients significantly enhanced the degradation rate of the fuel oil in rocks, granite tiles or sand. PAH degradation up to 80% was determined in sand and tiles. In tiles the oxygen content of the residual oil increased from 1.6% up to 8% in 90 days, which could be explained by the accumulation of products coming from the partial oxidation of the hydrocarbons. Eighteen months after the spill, the rocks of the beach were still coated by a black layer of weathered fuel oil. For this reason an oleophilic product, sunflower biodiesel was tested on a rock. The application of biodiesel accelerated the gradually clean-up of the polluted surface and could also accelerate the degradation of the residual oil.

Biodegradation, Environmental↗

PubMed2006

Granulation in high-load denitrifying upflow sludge bed (USB) pulsed reactors.

In this work, the effect of the application of a pulse system to anoxic upflow sludge bed (USB) denitrifying reactors for enhancing sludge granulation was studied. In all, three 0.8 L reactors (two operated with flow pulsation, P1 with effluent recycling and P2 without recycling, and one without pulsation and effluent recycling, no pulsation (NP)) were fed with a mixture of NaNO3 and glucose and inoculated with methanogenic granular sludge. The organic loading rate (OLR) and the nitrogen loading rate (NLR) were progressively increased and, at the end of the experiment, extremely high values were obtained (67.5 kgCOD/m3d and 11.25 kgN-NO3-/m3 d). Ammonia and nitrite accumulation in reactor NP were important in the maturation stage, decreasing the denitrification efficiency to 90%, while in reactor P1 only low nitrite values were obtained in the last few days of the experiment. In reactor P2, nitrogen removal was 100% most of the time. Several operational problems (flotation and the subsequent wash out of biomass) appeared in the NP reactor when working at high denitrifying loading rates, while in reactors P1 and P2 there were no notable problems, mainly due to the good characteristics of the sludge developed and the efficient degasification produced by the pulsing flow. The sludge formed in the NP reactor presented a flocculent structure and a total disintegration of the initial methanogenic granules occurred, while a small-sized granular biomass with a high specific density was developed in the pulsed reactors due to the shear stress produced.

Ammonia↗

PubMed2006

Comparison between the conventional anaerobic digestion of sewage sludge and its combination with a chemical or thermal pre-treatment concerning the removal of pharmaceuticals and personal care products.

Many novel treatment technologies, usually representing a pre-treatment prior to the biological degradation process, have been developed in order to improve the recycling and reuse of sewage sludge. Among all the methods available, a chemical (alkaline) and a thermal treatment have been considered in this study. The behaviour of 13 substances belonging to different therapeutic classes (musks, tranquillisers, antiepileptic, anti-inflammatories, antibiotics, X-ray contrast media and estrogens) has been studied during the anaerobic digestion of sewage sludge combined with these pre-treatments (advanced operation) in comparison with the conventional process. Two parameters have been analysed: the temperature (mesophilic and thermophilic conditions) and the sludge retention time. While organic matter solubilization was higher with the alkaline process (55-80%), no difference between both pre-treatments was observed concerning volatile solids solubilization (up to 20%). The removal efficiencies of solids and organic matter during anaerobic digestion ranged from 40-70% and 45-75%, respectively. The higher removal efficiencies of pharmaceuticals and personal care products were achieved for the antibiotics, Naproxen and the natural estrogens (>80%). For the other compounds, the values were in the range 20-70%, except for Carbamazepine, which was not removed at any condition tested.

Alkalies↗

PubMed2006

A hydrogen-based variable-gain controller for anaerobic digestion processes.

An easy-to-implement controller based on gas phase measurements for anaerobic digestion processes was developed. The controller is based on the indirect control of COD in the effluent by means of controlling the hydrogen concentration in the biogas. The fast response of hydrogen under destabilizations, such as those caused by overloads, guarantees an early actuation on the system before it destabilizes. The controller is designed such that it brings the anaerobic digestion process to maximum capacity by pushing it to maximum methane production as long as hydrogen remains low. Experiments have been conducted to test the controller under organic over- and underload situations and promising performance was achieved. Further experiments must be carried out to validate the controller under a wider spectrum of situations to enable its robust industrial application.

Anaerobiosis↗

PubMed2006

Variable stoichiometry with thermodynamic control in ADM1.

The effect of a variable stoichiometry of the carbohydrate fermentation process in the IWA Anaerobic Digestion Model No.1 (ADM1) is investigated. Most existing anaerobic digestion models including ADM1 consider a fixed-stoichiometry for their conversion processes. The ADM1 model was first transformed into an only mol based model to remove some errors derived from the mixed COD-mol based standard model and to allow for implementation of the variable stoichiometry. Consequently, the values of the butyrate and acetate catabolic yields of carbohydrate fermentation are made dependent on the hydrogen concentration and the reactor pH according to the predictions of a recently developed mixed culture fermentation model based on thermodynamic considerations. The simulation results obtained showed no significantly different responses in terms of effluent quality and system robustness between the standard and the variable stoichiometry ADM1 under overload conditions, and for both single- and two-step anaerobic digestion configurations. This behaviour is explained by the non-limiting acetogenic activity that compensated for the changes in the acidogenic products, typical behaviour for serial processes close to equilibrium. Based on the results obtained, thermodynamic rather than kinetic control for these conversions is suggested. Depending on the objectives to be met, lumping of carbohydrate fermenters and oxidative acetogens into a single biomass group with a variable stoichiometry is proposed for further consideration.

Anaerobiosis↗

PubMed2005

An anaerobic bioreactor allows the efficient degradation of HCH isomers in soil slurry.

The insecticide gamma-hexachlorocyclohexane (gamma-HCH or lindane), which has been extensively used for agricultural and medical purposes, presents high persistence and toxicity to the environment and low solubility. This study intends to assess the efficiency of an anaerobic reactor to degrade HCH isomers contained in soil slurry cultures. This study was developed in two phases: experiments in flasks to optimize the process parameters, and assessment of the slurry process in the anaerobic slurry reactor operated for an approximate period of a year. The influence of different environmental conditions was evaluated: the HCH concentration (25-100 mg HCH kg-1), the type of substrate (volatile fatty acids or starch), the sludge concentration (2-8 g VSS l-1) and the replacement of spiked soil to simulate a fed-batch operation (10-50%). The best results were obtained when the reactor was operated with a sludge concentration of 8 g VSS l-1, starch concentration of 2 g COD l-1 and soil replacements of 10-20%. Under these conditions, alpha- and gamma-HCH were completely degraded after 10d while nearly 90% beta- and delta-HCH were removed only after 50 d. According to the obtained results related to the total degradation of the HCH isomers and the degradation rates, especially high for alpha- and gamma-HCH, the anaerobic slurry reactor appears to be a good alternative for the degradation of the HCH isomers present in polluted soil.

Anaerobiosis↗

PubMed2005

Anaerobic treatment of azo dye Acid Orange 7 under fed-batch and continuous conditions.

Acid Orange 7 (AO7) was treated anaerobically under fed-batch and continuous conditions. Fed-batch assays carried out with and without cosubstrate showed that the removal rate of this dye is highly favourable when glucose is added as cosubstrate. In addition, some intermediates generated after the reductive breakdown of AO7, such as 1-amino-2-naphthol (1A2N), seem to play a significant role as redox mediators, thus increasing the degradation rate of the dye. This effect is evidenced by the fact that, during the first feeding, the maximum AO7 removal rate was achieved after a lag phase, whereas for further AO7 feedings this phase was not observed. This can be explained by the presence of 1-amino-2-naphthol in the medium. During the continuous treatment with UASB reactors, AO7 loading rates of 1.7 mM d(-1) (590 mg l(-1)d(-1)) were achieved, with 92% AO7 removal efficiencies, operating with an influent comprised of AO7 (0.58 mM) and glucose (2 gl(-1)). In addition, when the cosubstrate was limiting (AO7 0.3 mM and glucose 0.25 gl(-1)), AO7 removal was significantly lower (78%).

Azo Compounds↗

PubMed2005

An integrated system to remote monitor and control anaerobic wastewater treatment plants through the internet.

The TELEMAC project brings new methodologies from the Information and Science Technologies field to the world of water treatment. TELEMAC offers an advanced remote management system which adapts to most of the anaerobic wastewater treatment plants that do not benefit from a local expert in wastewater treatment. The TELEMAC system takes advantage of new sensors to better monitor the process dynamics and to run automatic controllers that stabilise the treatment plant, meet the depollution requirements and provide a biogas quality suitable for cogeneration. If the automatic system detects a failure which cannot be solved automatically or locally by a technician, then an expert from the TELEMAC Control Centre is contacted via the internet and manages the problem.

Automation↗

PubMed2005

Removal of pharmaceutically active compounds in nitrifying-denitrifying plants.

The behaviour of nine pharmaceutically active compounds (PhACs) of different diagnostic groups is studied during a nitrifying-denitrifying process in an activated sludge system. The compounds selected cover a wide range of frequently used substances such as anti-epileptics (carbamazepine), tranquillisers (diazepam), anti-depressants (fluoxetine and citalopram), anti-inflammatories (ibuprofen, naproxen and diclofenac) and estrogens (estradiol and ethinylestradiol). The main objective of this research is to investigate the effect of acclimation of biomass on the removal rates of these compounds, either by maintaining a high sludge retention time or at long-term operation. The removal rates achieved for nitrogen and carbon in the experimental unit exceed 90% and were not affected by the addition of PhACs. Carbamazepine, diazepam and diclofenac were only removed to a small extent. On the other hand, higher removal rates have been observed for naproxen and ibuprofen (68% and 82%), respectively.

Biodegradation, Environmental↗

PubMed2005

Behaviour of pharmaceuticals and personal care products in a sewage treatment plant of northwest Spain.

Thirteen pharmaceutical and cosmetic compounds have been surveyed along the different units of a municipal sewage treatment plant (STP) to study their fate across each step and the overall removal efficiency. The STP studied corresponds to a population of approximately 100,000 inhabitants located in Galicia (northwest Spain), including three main sections: pre-treatment (coarse and fine screening, grit and fat removal); primary treatment (sedimentation tanks); and secondary treatment (conventional activated sludge). Among all the substances considered (galaxolide, tonalide, carbamazepine, diazepam, diclofenac, ibuprofen, naproxen, estrone, estradiol, ethinylestradiol, roxitromycin, sulfamethoxazole and iopromide), only significant concentrations were found for two musks (galaxolide and tonalide), two antiphlogistics (ibuprofen and naproxen), two natural estrogens (estrone, estradiol), one antibiotic (sulfamethoxazole) and the X-ray contrast media (iopromide), being the other compounds below the quantification level. In the primary treatment, only the fragrances were partly removed, with efficiencies of 20-50% for galaxolide and tonalide. However, the aerobic treatment caused an important reduction in all compounds detected, between 35 and 75%, with the exception of iopromide. The overall removal efficiency of the STP ranged between 70 and 90% for the fragrances, 45 and 70% for the acidic compounds, around 67% for estradiol and 57% for the antibiotic sulfamethoxazole.

Adsorption↗

PubMed2004

Effect of pH on the stability of Pleurotus eryngii versatile peroxidase during heterologous production in Emericella nidulans.

Complementary DNA (cDNA) encoding the new versatile peroxidase from the ligninolytic basidiomycete Pleurotus eryngii has been expressed in the ascomycete Emericella nidulans. In recombinant E. nidulans cultures, the pH reached values as high as 8.3, correlating with a sharp decrease in peroxidase activity. Peroxidase was rapidly inactivated at alkaline pH, but was comparatively stable at acidic pH. The peroxidase inactivation in alkaline buffer could be reversed by adding Ca(2+) and lowering the pH. However, reactivation did not result after incubating the enzyme in non-buffered E. nidulans cultures that reached pH 7.5. To optimize recombinant peroxidase production, the effect of controlling the pH in E. nidulans bioreactor cultures was studied. An extended growth period, and a significant increase in the recombinant peroxidase level (5.3-fold higher activity than in the bioreactor without pH control) was obtained when the pH was maintained at 6.8, showing that culture pH is an important parameter for recombinant peroxidase production.

Bioreactors↗

PubMed2004

Anaerobic and aerobic continuous cultures of Saccharomyces cerevisiae: comparison of plasmid stability and EXG1 gene expression.

Two bioreactor continuous cultures, at anaerobic and aerobic conditions, were carried out using a recombinant Saccharomyces cerevisiae strain that over-expresses the homologous gene EXG1. This recombinant system was used to study the effect of dissolved oxygen concentration on plasmid stability and gene over-expression. Bioreactor cultures were operated at two dilution rates (0.14 and 0.03 h(-1)) to investigate the effect of other process parameters on EXG1 expression. Both cultures suffered severe plasmid instability during the first 16 generations. Segregational plasmid loss rate for the aerobic culture was two-fold that of the anaerobic operation. In spite of this fact, exo-beta-glucanase activity at aerobic conditions was 12-fold that of the anaerobic culture. This maximal activity (30 U ml(-1)) was attained at the lowest dilution rate when biomass reached its greatest value and glucose concentration was zero.

Aerobiosis↗

PubMed2003

Coupled BAS and anoxic USB system to remove urea and formaldehyde from wastewater.

Wastewater containing formaldehyde and urea was treated using a coupled system consisting of a biofilm airlift suspension (BAS) reactor and an anoxic upflow sludge blanket (USB) reactor. The anoxic USB reactor was used to carry out denitrification and urea hydrolysis, while the BAS reactor was used to carry out nitrification. In a first step, individual experiments were carried out to investigate the effects of both compounds on the nitrifying and denitrifying biomass. The BAS reactor was fed with a synthetic medium containing 500 mg N-NH4(+)l(-1) and 100mg N-urea l(-1), that were added continuously to this medium. Neither urea hydrolysis nor inhibition of nitrification was observed. Nitrification efficiency decreased when formaldehyde was fed during shocks at concentrations of 40, 80 and 120 mg C-formaldehyde l(-1). The anoxic USB reactor was fed with a synthetic medium containing nitrate, formaldehyde and urea. Concentrations of formaldehyde in the reactor of 100-120 mg C-formaldehyde l(-1) caused a decrease in the denitrification and urea hydrolysis rates. In a second step, the coupled system was operated at recycling ratios (R) of 3 and 9. Fed C/N ratios of 0.58, 1.0 and 1.5 g C-formaldehyde g(-1) N-NH4(+) were used for every recycling ratio. The maximum nitrogen removal percentages were achieved at a C/N ratio of 1.0 g C-formaldehyde g(-1) N-NH4(+) for both recycling ratios. A fed C/N ratio of 1.5 g C-formaldehyde g(-1) N-NH4(+) caused a decrease in the efficiency of the system with respect to nitrogen removal, due to the presence of formaldehyde in the BAS reactor, which decreased the nitrification. Formaldehyde was completely removed in the BAS reactor and a heterotrophic layer formed around the nitrifying biofilm.

Biofilms↗

PubMed2003

Improvement of the properties of granular sludge in UASB reactors by flow pulsation.

The objective of this work is to improve the characteristics of granular sludge by modification of the hydraulics of the bed through flow pulsation. Three UASB reactors, two operated with pulsing flow (P1 and P2) and a third without pulsation (NP), were started-up. Both recycling and feeding flow were pulsed in the reactor P1, while in reactor P2, only the feeding was pulsed. A high increase in the removal capacity and stability were achieved by applying pulsation in reactors P1 and P2 when compared to the non-pulsed one. Besides, pulsation promotes the formation of particles of smaller size and higher porosity, thus increasing the specific surface of the bed and consequently, the specific activity. In fact, while reactors P1 and P2 had a 95% COD removal when working at high organic loading rates (12 kg COD/m3 x d), reactor NP only reached 6 kg COD/m3 x d with 85% of removal capacity.

Biomass↗

PubMed2003

Modeling of the Acid Orange 7 anaerobic biodegradation.

It was found that 1-amino-2-naphthol, an intermediate generated during the anaerobic degradation of Acid Orange 7, is a redox mediator which plays a significant role in the transport of electrons to the dye, thus giving to the whole process an autocatalytic nature. Evidences of the autocatalytic behaviour were observed in experimental data previously obtained under batch and fed-batch conditions. In this paper, a kinetic model considering all these factors is proposed and validated. In batch assays, this model agrees satisfactorily with the experimental data. In the case of fed-batch assays, the autocatalytic model only can be applied satisfactorily after the first feeding, since the degradation of Acid Orange 7 after the second and third feedings followed a first-order kinetic. This fact can be explained due to the presence of the redox mediator previously generated during the reactions that took place after the first feeding.

Azo Compounds↗

PubMed2003

A membrane assisted hybrid bioreactor for the post treatment of an anaerobic effluent from a fish canning factory.

An innovative membrane assisted hybrid bioreactor was used to treat a mixture of two streams produced in a fish canning factory: a highly loaded stream that had previously been treated in an anaerobic contact reactor, and a second stream with a relatively low COD and N concentration. Experiments were carried out during two experimental stages: an aerobic stage, which is focused in the study on the aerobic oxidation of ammonia and COD and a nitrification-denitrification stage in which the study was mainly focused on the removal of nitrogen. Results of the aerobic period pointed out that it was feasible to achieve ammonia and COD removals of around 99% at OLR of 6.5 kg COD/m3 x d and NLR of 1.8 kg N-NH4+/m3 x d. Specific nitrifying activities of up to 0.78 g N-NH4+/g protein x d and 0.25 g N-NH4+/g VSS x d, were recorded for the attached and suspended biomass, respectively. Around 50-60% of the nitrifying capacity of the reactor was a result of the nitrifying capacity of the biofilm. During the nitrification-denitrification stage 76% of nitrogen removal was attained at an NLR of 0.8 kg N-NH4+/m3 x d. The biofilm nitrifying activity was not affected by the operating conditions of the system, as a result of the preferential consumption of COD by suspended biomass in the reactor. Thus, the combination of a hybrid system, with both suspended and attached biomass, and an ultrafiltration membrane module might be an alternative for treating wastewaters in compact biological systems. The intrinsic characteristics of the system made it feasible to operate at high OLR without problems related with the settling properties of the sludge or the drop in the nitrogen conversion. There were no solids in the effluent as a result of the use of the membrane filtration module.

Bacteria, Anaerobic↗