RESUMO
The surgical incision plays a pivotal role in any surgical procedure. A good surgical approach should allow optimal visualization, respect the anatomy and ensure the best aesthetic outcome possible, especially when the lesions involve the face. In this retrospective study, carried out from June 2014 to April 2018, different types of surgical approaches to perform mandibular reconstruction were compared. Twentyone patients who underwent mandibular reconstruction with free fibular flap (FFFs) using CAD-CAM technology and Virtual Surgical Planning (VSP) were included in the study, regardless the condition, the timing of reconstruction (primary vs secondary), the number of fibular segments or the type and size of the mandibular defect. The patients were treated for mandibular defects secondary to benign or low-grade oncological lesions and different non-oncological conditions. However, patients requiring neck dissection were excluded from the study. Patients were divided into two groups according to the type of surgical approach used: 7 patients received a traditional transcervical approach together with an intraoral approach, while 14 patients were operated through an intraoral approach combined with different microinvasive approaches, including the sub-mandibular, the retro-mandibular and the preauricular approaches. Different factors were statistically compared: characteristics of the harvested fibula, surgical timing, days of hospitalization, as well as complication, functional and aesthetic outcomes. According to this study, no statistically significant differences were observed between the two groups in any of the features considered. These results support the hypothesis that the combination of different microinvasive approaches and the traditional approach are superimposable, and they can be safely exchanged when the underlying defects allow it.
Assuntos
Retalhos de Tecido Biológico , Reconstrução Mandibular , Procedimentos de Cirurgia Plástica , Desenho Assistido por Computador , Fíbula/cirurgia , Retalhos de Tecido Biológico/cirurgia , Humanos , Mandíbula/cirurgia , Estudos RetrospectivosRESUMO
Huntington's disease (HD) has traditionally been described as a disorder purely of the brain; however, evidence indicates that peripheral abnormalities are also commonly seen. Among others, severe unintended body weight loss represents a prevalent and often debilitating feature of HD pathology, with no therapies available. It correlates with disease progression and significantly affects the quality of life of HD patients. Curcumin, a naturally occurring polyphenol with multiple therapeutic properties, has been validated to exert important beneficial effects under health conditions as well as in different pathological settings, including neurodegenerative and gastrointestinal (GI) disorders. Here, we investigated the potential therapeutic action that curcumin-supplemented diet may exert on central and peripheral dysfunctions in R6/2 mice, a well-characterized HD animal model which recapitulates some features of human pathology. Maintenance of normal motor function, protection from neuropathology and from GI dysfunction and preservation of GI emptying and conserved intestinal contractility, proved the beneficial role of life-long dietary curcumin in HD and corroborated the potential of the compound to be exploited to alleviate very debilitating symptoms associated with the disease.
Assuntos
Comportamento Animal/efeitos dos fármacos , Curcumina/administração & dosagem , Doença de Huntington/dietoterapia , Redução de Peso/efeitos dos fármacos , Animais , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Curcumina/farmacologia , Suplementos Nutricionais , Modelos Animais de Doenças , Feminino , Doença de Huntington/fisiopatologia , Masculino , Camundongos , Camundongos Transgênicos , Atividade Motora/efeitos dos fármacos , FenótipoRESUMO
The ARF protein functions as an important sensor of hyper-proliferative stimuli restricting cell proliferation through both p53-dependent and -independent pathways. Although to date the majority of studies on ARF have focused on its anti-proliferative role, few studies have addressed whether ARF may also have pro-survival functions. Here we show for the first time that during the process of adhesion and spreading ARF re-localizes to sites of active actin polymerization and to focal adhesion points where it interacts with the phosphorylated focal adhesion kinase. In line with its recruitment to focal adhesions, we observe that hampering ARF function in cancer cells leads to gross defects in cytoskeleton organization resulting in apoptosis through a mechanism dependent on the Death-Associated Protein Kinase. Our data uncover a novel function for p14ARF in protecting cells from anoikis that may reflect its role in anchorage independence, a hallmark of malignant tumor cells.
Assuntos
Anoikis/fisiologia , Adesão Celular/fisiologia , Proteína-Tirosina Quinases de Adesão Focal/metabolismo , Adesões Focais/metabolismo , Proteína Supressora de Tumor p14ARF/metabolismo , Apoptose/fisiologia , Linhagem Celular Tumoral , Proliferação de Células/fisiologia , Sobrevivência Celular/fisiologia , Citoesqueleto/metabolismo , Citoesqueleto/fisiologia , Proteínas Quinases Associadas com Morte Celular/metabolismo , Adesões Focais/fisiologia , Células HeLa , Humanos , Células MCF-7 , Fosforilação/fisiologia , Transdução de Sinais/fisiologiaRESUMO
Escherichia coli (E. coli) is one of the most commonly adopted indicators for the determination of the microbiological quality in water and treated wastewater. Two main types of methods are used for the enumeration of this faecal indicator: membrane filtration (MF) and enzyme substrate tests. For both types, several substrates based on the ß-D-glucuronidase activity have been commercialized. The specificity of this enzyme for E. coli bacteria has generated considerable use of methods that identify the ß-D-glucuronidase activity as a definite indication of the presence of E. coli, without any further confirmation. This approach has been recently questioned for the application to wastewater. The present study compares two methods belonging to the above-mentioned types for the enumeration of E. coli in wastewater: MF with Tryptone Bile X-glucuronide agar and the Colilert®-18 test. Confirmation tests showed low average percentages of false positives and false negatives for both enumeration methods (between 4 and 11%). Moreover, the counting capabilities of these two methods were compared for a set of 70 samples of wastewater having different origins and degrees of treatment. Statistical analysis showed that the Colilert®-18 test allowed on average for a significantly higher recovery of E. coli.
Assuntos
Proteínas de Bactérias/metabolismo , Monitoramento Ambiental/métodos , Escherichia coli/isolamento & purificação , Glucuronidase/metabolismo , Águas Residuárias/microbiologia , Monitoramento Ambiental/instrumentação , Escherichia coli/enzimologia , Filtração/métodosRESUMO
The interaction between the enteric microbiota and intestinal cells often involves signal molecules that affect both microbial behaviour and host responses. Examples of such signal molecules are the molecules secreted by bacteria that induce quorum sensing mechanisms in the producing microorganism and signal transduction pathways in the host cells. The pentapeptide competence and sporulation factor (CSF) of Bacillus subtilis is a well characterized quorum sensing factor that controls competence and spore formation in the producing bacterium and induces cytoprotective heat shock proteins in intestinal epithelial cells. We analysed several Bacillus strains isolated from human ileal biopsies of healthy volunteers and observed that some of them were unable to produce CSF but still able to act in a CSF-like fashion on model intestinal epithelial cells. One of those strains belonging to the Bacillus megaterium species secreted at least two factors with effects on intestinal HT29 cells: a peptide smaller than 3 kDa able to induce heat shock protein 27 (hsp27) and p38-MAPK, and a larger molecule able to induce protein kinase B (PKB/Akt) with a pro-proliferative effect.
Assuntos
Bacillus megaterium/fisiologia , Células Epiteliais/microbiologia , Bacillus megaterium/classificação , Bacillus megaterium/isolamento & purificação , Proteínas de Bactérias/metabolismo , Proteínas de Bactérias/uso terapêutico , Células CACO-2 , Ciclo Celular , Linhagem Celular Tumoral , Meios de Cultura , Células Epiteliais/citologia , Proteínas de Choque Térmico HSP27/metabolismo , Células HT29 , Humanos , Percepção de Quorum , Proteínas Repressoras/metabolismo , Proteínas Repressoras/uso terapêutico , Transdução de Sinais , Estresse FisiológicoRESUMO
Treated wastewater reuse is increasing in semi-arid regions as a response to the effects of climate change and increased competition for natural water resources. Investigating the fate of bacterial indicators is relevant to assess their persistence in the environment and possible transfer to groundwater or to the food chain. A long-term field-scale experimental campaign and a soil column test were carried out to evaluate the fate of the fecal indicator Escherichia coli (E. coli) in a cultivated soil when contaminated water resources are used for irrigation. For field experiments, fecal contamination was simulated by dosing the indicator to the effluent of a membrane bioreactor, thus simulating a filtration system's failure, and irrigating a test field where grass was grown. The presence of E. coli on grass and topsoil samples was monitored under different scenarios. For evaluating the fate of the same indicator in the subsoil, a set of soil columns was installed next to the field, operated, and monitored for E. coli concentration over time and along depth. Real municipal wastewater was used in this case as source of fecal contamination. Results showed that short- and medium-term effects on topsoil were strongly dependent on the concentration of E. coli in the irrigation water. Limited persistence and no relevant accumulation of the indicator on the grass and in the topsoil were observed. Watering events performed after fecal contamination did not influence significantly the decay in the topsoil, which followed a log-linear model. The trend of the E. coli concentrations in the leaching of the soil columns followed a log-linear model as well, suggesting bacterial decay as the dominant mechanism affecting the underground indicator's concentration.
Assuntos
Irrigação Agrícola , Escherichia coli/isolamento & purificação , Água Subterrânea/microbiologia , Águas Residuárias/microbiologia , Microbiologia da Água , Fezes/microbiologia , Poaceae/microbiologia , Microbiologia do Solo , Eliminação de Resíduos Líquidos/métodosRESUMO
Chemical-biological degradation of a widely spread antibacterial (nalidixic acid) was successfully obtained by an integrated membrane bioreactor (MBR)-ozonation process. The composition of the treated solution simulated the wastewater from the production of the target pharmaceutical, featuring high salinity and a relevant concentration of sodium acetate. Aim of treatment integration was to exploit the synergistic effects of chemical oxidation and bioprocesses, by adopting the latter to remove most of the COD and the ozonation biodegradable products. Integration was achieved by placing ozonation in the recirculation stream of the bioreactor effluent. The recirculation flow rate was three-fold the MBR feed, and the performance of the integrated system was compared to the standard polishing configuration (single ozonation step after the MBR). Results showed that the introduction of the ozonation step did not cause relevant drawbacks to both biological and filtration processes. nalidixic acid passed undegraded through the MBR and was completely removed in the ozonation step. Complete degradation of most of the detected ozonation products was better achieved with the integrated MBR-ozonation process than using the sequential treatment configuration, i.e. ozone polishing after MBR, given the same ozone dosage.
Assuntos
Reatores Biológicos , Ácido Nalidíxico/isolamento & purificação , Ozônio/químicaRESUMO
The treatment of a pharmaceutical wastewater resulting from the production of an antibacterial drug (nalidixic acid) was investigated employing a membrane bioreactor (MBR) integrated with either ozonation or UV/H(2)O(2) process. This was achieved by placing chemical oxidation in the recirculation stream of the MBR. A conventional configuration with chemical oxidation as polishing for the MBR effluent was also tested as a reference. The synergistic effect of MBR when integrated with chemical oxidation was assessed by monitoring (i) the main wastewater characteristics, (ii) the concentration of nalidixic acid, (iii) the 48 organics identified in the raw wastewater and (iv) the 55 degradation products identified during wastewater treatment. Results showed that MBR integration with ozonation or UV/H(2)O(2) did not cause relevant drawbacks to both biological and filtration processes, with COD removal rates in the range 85-95%. Nalidixic acid passed undegraded through the MBR and was completely removed in the chemical oxidation step. Although the polishing configuration appeared to give better performances than the integrated system in removing 15 out of 48 secondary organics while similar removals were obtained for 19 other compounds. The benefit of the integrated system was however evident for the removal of the degradation products. Indeed, the integrated system allowed higher removals for 34 out of 55 degradation products while for only 4 compounds the polishing configuration gave better performance. Overall, results showed the effectiveness of the integrated treatment with both ozone and UV/H(2)O(2).
Assuntos
Reatores Biológicos , Peróxido de Hidrogênio , Resíduos Industriais/análise , Compostos Orgânicos/química , Raios Ultravioleta , Eliminação de Resíduos Líquidos/métodos , Membranas Artificiais , Ácido Nalidíxico/química , Poluentes Químicos da Água/química , Purificação da ÁguaRESUMO
Membrane filtration was investigated at field scale in order to assess its effectiveness for reusing municipal effluents in agriculture. The study was started on April 2002 and ended on September 2007, as part of a national R&D project (AQUATEC). Preliminary results, which we already reported elsewhere, concerned the first two project years while this paper refers to the subsequent period. Three different crops (processing tomato, fennel and lettuce) were grown in rotation at a test field located in Apulia (Southern Italy) and irrigated with membrane filtered municipal secondary effluents. The quality of the reclaimed water was monitored chemically and microbiologically, and compared with conventional water pumped from a local well. Both water sources were used in parallel for irrigating two plots of the test field. The results showed that the microbiological quality of the treated wastewater was comparable to or even higher than that of the conventional source. Protozoan (oo)cysts were experimentally identified as effective indicators of possible failures of the filtration system. Moreover, long term heavy metals accumulation trends were monitored in soil and crops, showing that despite some lead and copper accumulation in the soil, no measurable increase of these metals was observed in the edible parts of the crops.
Assuntos
Agricultura , Conservação dos Recursos Naturais , Filtração/instrumentação , Filtração/métodos , Eliminação de Resíduos Líquidos/métodos , Cidades , Foeniculum , Itália , Lactuca , Solanum lycopersicum , Membranas Artificiais , Poluentes Químicos da Água/química , Purificação da Água/métodosRESUMO
The enhanced removal of organic compounds from a pharmaceutical wastewater resulting from the production of an anti-viral drug (acyclovir) was obtained by employing a membrane bioreactor (MBR) and an ozonation system. An integrated MBR-ozonation system was set-up by placing the ozonation reactor in the recirculation stream of the MBR effluent. A conventional treatment set-up (ozonation as polishing step after MBR) was also used as a reference. The biological treatment alone reached an average COD removal of 99%, which remained unvaried when the ozonation step was introduced. An acyclovir removal of 99% was also obtained with the MBR step and the ozonation allowed to further remove 99% of the residual concentration in the MBR effluent. For several of the 28 organics identified in the wastewater the efficiency of the MBR treatment improved from 20% to 60% as soon as the ozonation was placed in the recirculation stream. The benefit of the integrated system, with respect to the conventional treatment set-up was evident for the removal of a specific ozonation by-product. The latter was efficiently removed in the integrated system, being its abundance in the final effluent 20-fold lower than what obtained when ozonation was used as a polishing step. In addition, if the conventional treatment configuration is employed, the same performance of the integrated system in terms of by-product removal can only be obtained when the ozonation is operated for longer than 60 min. This demonstrates the effectiveness of the integrated system compared to the conventional polishing configuration.
Assuntos
Reatores Biológicos/microbiologia , Compostos Orgânicos/metabolismo , Ozônio/química , Preparações Farmacêuticas/metabolismo , Eliminação de Resíduos Líquidos , Aciclovir/metabolismo , Antivirais/metabolismo , Biodegradação Ambiental , Preparações Farmacêuticas/químicaRESUMO
INTRODUCTION: In 2009 the limit value of benzo(a)pyrene (BaP) in ambient air of 1.0 ng/m3 has been exceeded in the urban district of Taranto near to the industrial area, where a several large plants are located, including an integrated cycle steel plant. OBJECTIVE: To identify emission sources and quantify relative contribution to the PAHs levels; to estimate health impact associated to PAHs exposure in general population. METHODS: Multivariate receptor models have been used. Concentration of PAHs measured in 4 location in Taranto in 2008-2009 have been analyzed. 5 different models estimated profiles of unknown sources and identified significant chemical species. To compute the lung cancer risk the WHO unit risk estimate for BaP (8.7 x 10(5) ng/m3) has been adopted. RESULTS: Models employed identify 3 to 4 emission sources. Estimated profiles have been compared with measured ones. Based on the average annual BaP level measured (1.3 ng/m3), 2 attributable cancer cases in the district Taranto population are estimated to result from a life-time exposure. CONCLUSIONS: Among different emissive sources, the analysis identifies theoretical sources whose profiles, compared with observed data, allow to identify dominant contributions to PAHs pollution and to design corrective actions to reduce environmental and health impact.
Assuntos
Benzo(a)pireno/análise , Carcinógenos/análise , Exposição Ambiental/análise , Humanos , Itália , Medição de RiscoRESUMO
The biodegradability of different wastewater samples originated from the industrial production of three pharmaceuticals (naproxen, acyclovir, and nalidixic acid) was performed through the standard Zahn-Wellens test. Moreover, the wastewater composition before and during the test was evaluated in terms of parent compounds and main metabolites by LC/MS, and the biodegradability of the parent compounds was also assessed by performing extra Zahn-Wellens tests on synthetic solutions. The results, besides showing the relatively good biodegradability of acyclovir and naproxen, evidenced the masking role of the organic matrices, especially in the case of nalidixic acid. The latter compound showed to be recalcitrant and persistent, despite the apparently good performance of the Zahn-Wellens test. Deeper evaluation evidenced that the biodegradation of high concentrations of organic solvents and other biodegradable compound tended to "hide" the lack of removal of the target compound.
Assuntos
Bactérias Aeróbias/metabolismo , Reatores Biológicos , Resíduos de Drogas/metabolismo , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/metabolismo , Aciclovir/química , Aciclovir/metabolismo , Biodegradação Ambiental , Cromatografia Líquida , Resíduos de Drogas/química , Espectrometria de Massas , Estrutura Molecular , Ácido Nalidíxico/química , Ácido Nalidíxico/metabolismo , Naproxeno/química , Naproxeno/metabolismoRESUMO
Membrane bioreactors allow for higher sludge concentrations and improved degradation efficiencies with respect to conventional activated sludge. However, in the current practice these systems are often operated under sub-optimal conditions, since so far no precise indications have yet been issued on the optimal operating conditions of MBR for municipal wastewater treatment. This paper reports some results of four years of operation of a bench scale membrane bioreactor where steady state conditions were investigated under different sludge retention times. The whole experimental campaign was oriented towards the investigation of optimal process conditions in terms of COD removal and nitrification, biomass activity and growth, and sludge characteristics. The membrane bioreactor treated real municipal sewage, and four different sludge ages were tested (20, 40, 60, and 80 days) and compared with previous data on complete sludge retention. The results showed that the the biology of the system, as assessed by the oxygen uptake rate, is less affected than the sludge physical parameters. In particular, although the growth yield was observed to dramatically drop for SRT higher than 80 days, the biological activity was maintained under all the tested conditions. These considerations suggest that high SRT are convenient in terms of limited excess sludge production without losses of the treatment capacity. Physical characteristics such as the viscosity and the filterability appear to be negatively affected by prolonged sludge retention times, but their values remain within the ranges normally reported for conventional activated sludge.
Assuntos
Reatores Biológicos , Cidades , Laboratórios , Membranas Artificiais , Eliminação de Resíduos/métodos , Esgotos/química , Biomassa , Compostos de Nitrogênio/química , Fatores de TempoRESUMO
The rheological characterization is of crucial importance in sludge management both for biomass dewatering and stabilization purposes and for the definition of design parameters for sludge handling operations. The sludge retention time (SRT) has a significant influence on biomass properties in biological wastewater treatment systems and in particular in membrane bioreactors (MBR). The aim of this work is to compare the rheological behaviour of the biomass in a membrane bioreactor operated under different SRT. A bench scale MBR was operated for four years under the same conditions except for the SRT, that ranged from 20 days to complete sludge retention. The rheological properties were measured over time and the apparent viscosity was correlated with the concentration of solid material under equilibrium conditions. The three models most commonly adopted for rheological simulations were evaluated and compared in terms of their parameters. Steady state average values of these parameters were related to the equilibrium biomass concentration (MLSS). The models were tested to select the one better fitting the experimental data in terms of Mean Root Square Error (MRSE). The relationship between the apparent viscosity and the shear rate, as a function of solid concentration, was determined and proposed.
Assuntos
Esgotos , Biomassa , Reatores Biológicos , Cinética , Reologia , Viscosidade , Eliminação de Resíduos Líquidos/métodosRESUMO
Rheological characterization is of crucial importance in sludge management both in terms of biomass dewatering and stabilization properties and in terms of design parameters for sludge handling operations. The sludge retention time (SRT) has a significant influence on biomass properties in biological wastewater treatment systems and in particular in membrane bioreactors (MBRs). The aim of this work is to compare the rheological behaviour of the biomass in a MBR operated under different SRTs. A bench-scale MBR was operated for 4 years under the same conditions except for the SRT, which ranged from 20 days to complete sludge retention. The rheological properties were measured over time and the apparent viscosity was correlated with the concentration of solid material when equilibrium conditions were reached and maintained. The three models most commonly adopted for rheological simulations were evaluated and compared in terms of their parameters. Then, steady-state average values of these parameters were related to the equilibrium biomass concentration (MLSS). The models were tested to select the one better fitting the experimental data in terms of mean root square error (MRSE). The relationship between the apparent viscosity and the shear rate, as a function of solid concentration, was determined and is proposed here. Statistical analysis showed that, in general, the Bingham model provided slightly better results than the Ostwald one. However, considering that a strong correlation between the two parameters of the Ostwald model was found for all the SRTs tested, both in the transient growth phases and under steady-state conditions, this model might be used more conveniently. This feature suggests that the latter model is easier to be used for the determination of the sludge apparent viscosity.
Assuntos
Reatores Biológicos , Membranas Artificiais , Reologia , EsgotosRESUMO
The p14ARF tumor suppressor is a key regulator of cellular proliferation, frequently inactivated in human cancer. The mechanisms that regulate alternative reading frame (ARF) turnover have been obscure for long time, being ARF a relatively stable protein. Recently, it has been described that its degradation depends, at least in part, on the proteasome and that it can be subjected to N-terminal ubiquitination. We have previously reported that ARF protein levels are regulated by TBP-1 (Tat-Binding Protein 1), a multifunctional protein, component of the regulatory subunit of the proteasome, involved in different cellular processes. Here we demonstrate that the stabilization effect exerted by TBP-1 requires an intact N-terminal 39 amino acids in ARF and occurs independently from N-terminal ubiquitination of the protein. Furthermore, we observed that ARF can be degraded in vitro by the 20S proteasome, in the absence of ubiquitination and this effect can be counteracted by TBP-1. These observations seem relevant in the comprehension of the regulation of ARF metabolism as, among the plethora of cellular ARF's interactors already identified, only NPM/B23 and TBP-1 appear to be involved in the control of ARF intracellular levels.
Assuntos
Complexo de Endopeptidases do Proteassoma/metabolismo , Proteína Supressora de Tumor p14ARF/metabolismo , ATPases Associadas a Diversas Atividades Celulares , Sequência de Aminoácidos/genética , Células Cultivadas , Humanos , Peptídeos/genética , Peptídeos/metabolismo , Complexo de Endopeptidases do Proteassoma/genética , Proteína Supressora de Tumor p14ARF/genética , Ubiquitina/metabolismoRESUMO
Sludge physical characteristics play an important role in the operation of membrane bioreactors (MBR) due to their influence on filtration and their effects on handling of excess sludge. These systems are designed to maintain high solid concentrations, thus limiting sludge production and the related operational costs of the process. In this study, the sludge from a bench scale MBR operated for about 1 year with complete solid retention was investigated to assess its physical and rheological properties. Concentrations of mixed liquor suspended solids (MLSS) up to 24 gTSSL(-1) affected the diluted sludge volume index (DSVI), the capillary suction time (CST), the specific resistance to filtration (SRF) and the compressibility (s). The MBR sludge displayed similar dewatering properties of conventional waste activated sludge, suggesting that the upgrade of wastewater treatment plants with the MBR technology would not affect the behaviour of the dewatering equipment. The apparent viscosity was expressed as a function of the MLSS and the experimental data were interpreted by comparing different models. Ostwald model was chosen, and two equations for viscosity were proposed. The thixotropy of MBR sludge was also evaluated by measuring the reduced hysteresis area (rHa) and relating this parameter to the characteristics of the sludge. The evaluation of energy consumption for mixing evidenced that, under the tested conditions, the increase of solid concentration from 3 to 30 gTSSL(-1) resulted in a limited increase of energy requirements (25-30%).
Assuntos
Reatores Biológicos , Esgotos , Biomassa , Filtração , ReologiaRESUMO
A wastewater tertiary treatment system based on membrane ultrafiltration and fed with secondary-treated municipal wastewater was evaluated for its Giardia cyst and Cryptosporidium oocyst removal efficiency. Giardia duodenalis (assemblages A and B) and Cryptosporidium parvum were identified in feed water but were found in filtered water only during occasional failure of the filtration system.
Assuntos
Cryptosporidium/isolamento & purificação , Água Doce/parasitologia , Giardia/isolamento & purificação , Ultrafiltração , Purificação da Água/métodos , Agricultura , Animais , Cidades , Cryptosporidium/crescimento & desenvolvimento , Giardia/crescimento & desenvolvimento , Membranas Artificiais , Filtros Microporos , Oocistos/crescimento & desenvolvimento , Ultrafiltração/instrumentação , Ultrafiltração/métodos , Eliminação de Resíduos Líquidos/métodosRESUMO
The removal of odours from wastewater treatment plants through diffusion of odour-containing air volumes into the aerated basins was investigated in a bench scale experimental campaign which lasted more than 200 days. Hydrogen sulphide was selected as a model odorous compound and its removal efficiencies were experimentally evaluated along with its effects on the biomass and on the main biochemical processes. Two bench scale sequencing batch reactors were fed in parallel on real primary sewage and monitored for chemical oxygen demand removal, nitrification and denitrification. The balance of H2S was also monitored after adding to one of them a Na2S liquid solution of 17 mgS l(reactor)(-1) d(-1), corresponding to a gas-phase concentration of 240 mgS (Nm3)(-1). Results showed an average sulphide removal of 94% in the reactor supplied with Na2S. Moreover, microbial composition did not show relevant variations after the addition of sulphide, and the good features of activated sludge flocs were maintained also in terms of sludge settleability. No relevant effects of sulphide were detected on carbon and nitrogen metabolism and chemical oxygen demand removal, nitrification and denitrification efficiencies were always above 75%, 95%, and 50% respectively, and comparable across the two reactors.
Assuntos
Biomassa , Sulfeto de Hidrogênio/metabolismo , Odorantes , Esgotos/química , Amônia/análise , Difusão , Odorantes/análise , Oxigênio/metabolismoRESUMO
A rheological characterization of the sludge sampled from a complete retention membrane bioreactor was performed in order to correlate the apparent viscosity with the concentration of solids. The three most commonly adopted models were tested to select the one better fitting the experimental data. Ostwald model was choosen, and the relationship between the apparent viscosity and the shear rate was determined for mixed liquor suspended solids (MLSS) concentrations ranging between 9 and 25 g l(-1). Ostwald model parameters k and n were correlated with MLSS concentration, comparing linear, power, and exponential-power (only for k) laws in terms of R2 and Mean Root Square Error (MRSE). Both power and exponential-power functions provided good and comparable correlations for parameter k, while the linear relationship was much less accurate, especially at the highest solid concentrations. The parameter n was better modelled by a power function than by a linear one. Therefore two simulation models were proposed, both based on Ostwald's equation, where the two parameters k and n were expressed as functions of MLSS. Evaluation of energy consumption for mixing showed that the increase of solid concentration from 3 to 30 g l(-1) resulted in a limited increase in energy requirement (25-30 %). In real systems, where Reynolds numbers shift towards the turbulent regime, the increase of energy requirements for increasing solids concentration is even less pronounced. The thixotropy of membrane bioreactor sludge was also evaluated by measuring the rHa (reduced hysteresis area) and relating this parameter to the characteristics of the sludge growing within the reactor.